Merge RubyGems-3.2.11 and Bundler-2.2.11

32 files changed, 468 insertions, 449 deletions

diff --git a/lib/bundler/definition.rb b/lib/bundler/definition.rb
index 9178f0126f..3c25149d33 100644
--- a/lib/bundler/definition.rb
+++ b/lib/bundler/definition.rb
@@ -106,19 +106,6 @@ module Bundler
         @locked_platforms = []
       end
 
-      @locked_gem_sources = @locked_sources.select {|s| s.is_a?(Source::Rubygems) }
-      @disable_multisource = !Bundler.frozen_bundle? || @locked_gem_sources.none? {|s| s.remotes.size > 1 }
-
-      unless @disable_multisource
-        msg = "Your lockfile contains a single rubygems source section with multiple remotes, which is insecure. " \
-          "You should regenerate your lockfile in a non frozen environment."
-
-        Bundler::SharedHelpers.major_deprecation 2, msg
-
-        @sources.allow_multisource!
-        @locked_gem_sources.each(&:allow_multisource!)
-      end
-
       @unlock[:gems] ||= []
       @unlock[:sources] ||= []
       @unlock[:ruby] ||= if @ruby_version && locked_ruby_version_object
@@ -158,14 +145,6 @@ module Bundler
       end
     end
 
-    def disable_multisource?
-      @disable_multisource
-    end
-
-    def allow_multisource!
-      @disable_multisource = false
-    end
-
     def resolve_with_cache!
       raise "Specs already loaded" if @specs
       sources.cached!
@@ -285,7 +264,7 @@ module Bundler
           # Run a resolve against the locally available gems
           Bundler.ui.debug("Found changes from the lockfile, re-resolving dependencies because #{change_reason}")
           expanded_dependencies = expand_dependencies(dependencies + metadata_dependencies, @remote)
-          Resolver.resolve(expanded_dependencies, source_requirements, last_resolve, gem_version_promoter, additional_base_requirements_for_resolve, platforms)
+          Resolver.resolve(expanded_dependencies, index, source_requirements, last_resolve, gem_version_promoter, additional_base_requirements_for_resolve, platforms)
         end
       end
     end
@@ -551,9 +530,6 @@ module Bundler
     attr_reader :sources
     private :sources
 
-    attr_reader :locked_gem_sources
-    private :locked_gem_sources
-
     def nothing_changed?
       !@source_changes && !@dependency_changes && !@new_platform && !@path_changes && !@local_changes && !@locked_specs_incomplete_for_platform
     end
@@ -678,20 +654,21 @@ module Bundler
     end
 
     def converge_rubygems_sources
-      return false if disable_multisource?
+      return false if Bundler.feature_flag.disable_multisource?
 
-      return false if locked_gem_sources.empty?
+      changes = false
 
+      # Get the RubyGems sources from the Gemfile.lock
+      locked_gem_sources = @locked_sources.select {|s| s.is_a?(Source::Rubygems) }
       # Get the RubyGems remotes from the Gemfile
       actual_remotes = sources.rubygems_remotes
-      return false if actual_remotes.empty?
-
-      changes = false
 
       # If there is a RubyGems source in both
-      locked_gem_sources.each do |locked_gem|
-        # Merge the remotes from the Gemfile into the Gemfile.lock
-        changes |= locked_gem.replace_remotes(actual_remotes, Bundler.settings[:allow_deployment_source_credential_changes])
+      if !locked_gem_sources.empty? && !actual_remotes.empty?
+        locked_gem_sources.each do |locked_gem|
+          # Merge the remotes from the Gemfile into the Gemfile.lock
+          changes |= locked_gem.replace_remotes(actual_remotes, Bundler.settings[:allow_deployment_source_credential_changes])
+        end
       end
 
       changes
@@ -916,18 +893,30 @@ module Bundler
       # Record the specs available in each gem's source, so that those
       # specs will be available later when the resolver knows where to
       # look for that gemspec (or its dependencies)
-      source_requirements = { :default => sources.default_source }.merge(dependency_source_requirements)
+      default = sources.default_source
+      source_requirements = { :default => default }
+      default = nil unless Bundler.feature_flag.disable_multisource?
+      dependencies.each do |dep|
+        next unless source = dep.source || default
+        source_requirements[dep.name] = source
+      end
       metadata_dependencies.each do |dep|
         source_requirements[dep.name] = sources.metadata_source
       end
-      source_requirements[:global] = index unless disable_multisource?
       source_requirements[:default_bundler] = source_requirements["bundler"] || source_requirements[:default]
       source_requirements["bundler"] = sources.metadata_source # needs to come last to override
       source_requirements
     end
 
     def pinned_spec_names(skip = nil)
-      dependency_source_requirements.reject {|_, source| source == skip }.keys
+      pinned_names = []
+      default = Bundler.feature_flag.disable_multisource? && sources.default_source
+      @dependencies.each do |dep|
+        next unless dep_source = dep.source || default
+        next if dep_source == skip
+        pinned_names << dep.name
+      end
+      pinned_names
     end
 
     def requested_groups
@@ -984,18 +973,5 @@ module Bundler
 
       Bundler.settings[:allow_deployment_source_credential_changes] && source.equivalent_remotes?(sources.rubygems_remotes)
     end
-
-    def dependency_source_requirements
-      @dependency_source_requirements ||= begin
-        source_requirements = {}
-        default = disable_multisource? && sources.default_source
-        dependencies.each do |dep|
-          dep_source = dep.source || default
-          next unless dep_source
-          source_requirements[dep.name] = dep_source
-        end
-        source_requirements
-      end
-    end
   end
 end
diff --git a/lib/bundler/dsl.rb b/lib/bundler/dsl.rb
index ef5aaf669b..1cc7908b8a 100644
--- a/lib/bundler/dsl.rb
+++ b/lib/bundler/dsl.rb
@@ -24,9 +24,6 @@ module Bundler
     def initialize
       @source               = nil
       @sources              = SourceList.new
-
-      @global_rubygems_sources = []
-
       @git_sources          = {}
       @dependencies         = []
       @groups               = []
@@ -48,7 +45,6 @@ module Bundler
       @gemfiles << expanded_gemfile_path
       contents ||= Bundler.read_file(@gemfile.to_s)
       instance_eval(contents.dup.tap{|x| x.untaint if RUBY_VERSION < "2.7" }, gemfile.to_s, 1)
-      check_primary_source_safety
     rescue Exception => e # rubocop:disable Lint/RescueException
       message = "There was an error " \
         "#{e.is_a?(GemfileEvalError) ? "evaluating" : "parsing"} " \
@@ -168,7 +164,8 @@ module Bundler
       elsif block_given?
         with_source(@sources.add_rubygems_source("remotes" => source), &blk)
       else
-        @global_rubygems_sources << source
+        check_primary_source_safety(@sources)
+        @sources.global_rubygems_source = source
       end
     end
 
@@ -186,14 +183,24 @@ module Bundler
     end
 
     def path(path, options = {}, &blk)
+      unless block_given?
+        msg = "You can no longer specify a path source by itself. Instead, \n" \
+              "either use the :path option on a gem, or specify the gems that \n" \
+              "bundler should find in the path source by passing a block to \n" \
+              "the path method, like: \n\n" \
+              "    path 'dir/containing/rails' do\n" \
+              "      gem 'rails'\n" \
+              "    end\n\n"
+
+        raise DeprecatedError, msg if Bundler.feature_flag.disable_multisource?
+        SharedHelpers.major_deprecation(2, msg.strip)
+      end
+
       source_options = normalize_hash(options).merge(
         "path" => Pathname.new(path),
         "root_path" => gemfile_root,
         "gemspec" => gemspecs.find {|g| g.name == options["name"] }
       )
-
-      source_options["global"] = true unless block_given?
-
       source = @sources.add_path_source(source_options)
       with_source(source, &blk)
     end
@@ -272,11 +279,6 @@ module Bundler
       raise GemfileError, "Undefined local variable or method `#{name}' for Gemfile"
     end
 
-    def check_primary_source_safety
-      check_path_source_safety
-      check_rubygems_source_safety
-    end
-
     private
 
     def add_git_sources
@@ -438,40 +440,25 @@ repo_name ||= user_name
       end
     end
 
-    def check_path_source_safety
-      return if @sources.global_path_source.nil?
-
-      msg = "You can no longer specify a path source by itself. Instead, \n" \
-              "either use the :path option on a gem, or specify the gems that \n" \
-              "bundler should find in the path source by passing a block to \n" \
-              "the path method, like: \n\n" \
-              "    path 'dir/containing/rails' do\n" \
-              "      gem 'rails'\n" \
-              "    end\n\n"
+    def check_primary_source_safety(source_list)
+      return if source_list.rubygems_primary_remotes.empty? && source_list.global_rubygems_source.nil?
 
-      SharedHelpers.major_deprecation(2, msg.strip)
-    end
-
-    def check_rubygems_source_safety
-      if @global_rubygems_sources.size <= 1
-        @sources.global_rubygems_source = @global_rubygems_sources.first
-        return
-      end
-
-      @global_rubygems_sources.each do |source|
-        @sources.add_rubygems_remote(source)
-      end
-
-      if Bundler.feature_flag.bundler_3_mode?
+      if Bundler.feature_flag.disable_multisource?
         msg = "This Gemfile contains multiple primary sources. " \
           "Each source after the first must include a block to indicate which gems " \
           "should come from that source"
+        unless Bundler.feature_flag.bundler_2_mode?
+          msg += ". To downgrade this error to a warning, run " \
+            "`bundle config unset disable_multisource`"
+        end
         raise GemfileEvalError, msg
       else
         Bundler::SharedHelpers.major_deprecation 2, "Your Gemfile contains multiple primary sources. " \
           "Using `source` more than once without a block is a security risk, and " \
           "may result in installing unexpected gems. To resolve this warning, use " \
-          "a block to indicate which gems should come from the secondary source."
+          "a block to indicate which gems should come from the secondary source. " \
+          "To upgrade this warning to an error, run `bundle config set --local " \
+          "disable_multisource true`."
       end
     end
 
diff --git a/lib/bundler/feature_flag.rb b/lib/bundler/feature_flag.rb
index 9b7172fa35..a1b443b042 100644
--- a/lib/bundler/feature_flag.rb
+++ b/lib/bundler/feature_flag.rb
@@ -32,6 +32,7 @@ module Bundler
     settings_flag(:cache_all) { bundler_3_mode? }
     settings_flag(:default_install_uses_path) { bundler_3_mode? }
     settings_flag(:deployment_means_frozen) { bundler_3_mode? }
+    settings_flag(:disable_multisource) { bundler_3_mode? }
     settings_flag(:forget_cli_options) { bundler_3_mode? }
     settings_flag(:global_gem_cache) { bundler_3_mode? }
     settings_flag(:only_update_to_newer_versions) { bundler_3_mode? }
diff --git a/lib/bundler/inline.rb b/lib/bundler/inline.rb
index 02da06cee9..59211193d4 100644
--- a/lib/bundler/inline.rb
+++ b/lib/bundler/inline.rb
@@ -50,7 +50,6 @@ def gemfile(install = false, options = {}, &gemfile)
     Bundler::Plugin.gemfile_install(&gemfile) if Bundler.feature_flag.plugins?
     builder = Bundler::Dsl.new
     builder.instance_eval(&gemfile)
-    builder.check_primary_source_safety
 
     Bundler.settings.temporary(:frozen => false) do
       definition = builder.to_definition(nil, true)
diff --git a/lib/bundler/lockfile_parser.rb b/lib/bundler/lockfile_parser.rb
index 058d353bbe..f836737621 100644
--- a/lib/bundler/lockfile_parser.rb
+++ b/lib/bundler/lockfile_parser.rb
@@ -64,6 +64,8 @@ module Bundler
       @state        = nil
       @specs        = {}
 
+      @rubygems_aggregate = Source::Rubygems.new
+
       if lockfile.match(/<<<<<<<|=======|>>>>>>>|\|\|\|\|\|\|\|/)
         raise LockfileError, "Your #{Bundler.default_lockfile.relative_path_from(SharedHelpers.pwd)} contains merge conflicts.\n" \
           "Run `git checkout HEAD -- #{Bundler.default_lockfile.relative_path_from(SharedHelpers.pwd)}` first to get a clean lock."
@@ -87,6 +89,7 @@ module Bundler
           send("parse_#{@state}", line)
         end
       end
+      @sources << @rubygems_aggregate unless Bundler.feature_flag.disable_multisource?
       @specs = @specs.values.sort_by(&:identifier)
       warn_for_outdated_bundler_version
     rescue ArgumentError => e
@@ -131,19 +134,16 @@ module Bundler
             @sources << @current_source
           end
         when GEM
-          source_remotes = Array(@opts["remote"])
-
-          if source_remotes.size == 1
+          if Bundler.feature_flag.disable_multisource?
             @opts["remotes"] = @opts.delete("remote")
             @current_source = TYPES[@type].from_lock(@opts)
+            @sources << @current_source
           else
-            source_remotes.each do |url|
-              rubygems_aggregate.add_remote(url)
+            Array(@opts["remote"]).each do |url|
+              @rubygems_aggregate.add_remote(url)
             end
-            @current_source = rubygems_aggregate
+            @current_source = @rubygems_aggregate
           end
-
-          @sources << @current_source
         when PLUGIN
           @current_source = Plugin.source_from_lock(@opts)
           @sources << @current_source
@@ -245,9 +245,5 @@ module Bundler
     def parse_ruby(line)
       @ruby_version = line.strip
     end
-
-    def rubygems_aggregate
-      @rubygems_aggregate ||= Source::Rubygems.new
-    end
   end
 end
diff --git a/lib/bundler/man/bundle-config.1 b/lib/bundler/man/bundle-config.1
index da628a7dcc..00bb708240 100644
--- a/lib/bundler/man/bundle-config.1
+++ b/lib/bundler/man/bundle-config.1
@@ -56,6 +56,9 @@ Executing \fBbundle config unset \-\-local <name> <value>\fR will delete the con
 .P
 Executing bundle with the \fBBUNDLE_IGNORE_CONFIG\fR environment variable set will cause it to ignore all configuration\.
 .
+.P
+Executing \fBbundle config set \-\-local disable_multisource true\fR upgrades the warning about the Gemfile containing multiple primary sources to an error\. Executing \fBbundle config unset disable_multisource\fR downgrades this error to a warning\.
+.
 .SH "REMEMBERING OPTIONS"
 Flags passed to \fBbundle install\fR or the Bundler runtime, such as \fB\-\-path foo\fR or \fB\-\-without production\fR, are remembered between commands and saved to your local application\'s configuration (normally, \fB\./\.bundle/config\fR)\.
 .
@@ -181,6 +184,9 @@ The following is a list of all configuration keys and their purpose\. You can le
 \fBdisable_local_revision_check\fR (\fBBUNDLE_DISABLE_LOCAL_REVISION_CHECK\fR): Allow Bundler to use a local git override without checking if the revision present in the lockfile is present in the repository\.
 .
 .IP "\(bu" 4
+\fBdisable_multisource\fR (\fBBUNDLE_DISABLE_MULTISOURCE\fR): When set, Gemfiles containing multiple sources will produce errors instead of warnings\. Use \fBbundle config unset disable_multisource\fR to unset\.
+.
+.IP "\(bu" 4
 \fBdisable_shared_gems\fR (\fBBUNDLE_DISABLE_SHARED_GEMS\fR): Stop Bundler from accessing gems installed to RubyGems\' normal location\.
 .
 .IP "\(bu" 4
diff --git a/lib/bundler/man/bundle-config.1.ronn b/lib/bundler/man/bundle-config.1.ronn
index 81d0603e8b..dc99c69412 100644
--- a/lib/bundler/man/bundle-config.1.ronn
+++ b/lib/bundler/man/bundle-config.1.ronn
@@ -47,6 +47,10 @@ configuration only from the local application.
 Executing bundle with the `BUNDLE_IGNORE_CONFIG` environment variable set will
 cause it to ignore all configuration.
 
+Executing `bundle config set --local disable_multisource true` upgrades the warning about
+the Gemfile containing multiple primary sources to an error. Executing `bundle
+config unset disable_multisource` downgrades this error to a warning.
+
 ## REMEMBERING OPTIONS
 
 Flags passed to `bundle install` or the Bundler runtime, such as `--path foo` or
@@ -174,6 +178,10 @@ learn more about their operation in [bundle install(1)](bundle-install.1.html).
 * `disable_local_revision_check` (`BUNDLE_DISABLE_LOCAL_REVISION_CHECK`):
    Allow Bundler to use a local git override without checking if the revision
    present in the lockfile is present in the repository.
+* `disable_multisource` (`BUNDLE_DISABLE_MULTISOURCE`):
+   When set, Gemfiles containing multiple sources will produce errors
+   instead of warnings.
+   Use `bundle config unset disable_multisource` to unset.
 * `disable_shared_gems` (`BUNDLE_DISABLE_SHARED_GEMS`):
    Stop Bundler from accessing gems installed to RubyGems' normal location.
 * `disable_version_check` (`BUNDLE_DISABLE_VERSION_CHECK`):
diff --git a/lib/bundler/plugin.rb b/lib/bundler/plugin.rb
index dddb468582..da3f468da5 100644
--- a/lib/bundler/plugin.rb
+++ b/lib/bundler/plugin.rb
@@ -105,7 +105,6 @@ module Bundler
         else
           builder.eval_gemfile(gemfile)
         end
-        builder.check_primary_source_safety
         definition = builder.to_definition(nil, true)
 
         return if definition.dependencies.empty?
diff --git a/lib/bundler/plugin/installer.rb b/lib/bundler/plugin/installer.rb
index 73198aec04..26cec4f18c 100644
--- a/lib/bundler/plugin/installer.rb
+++ b/lib/bundler/plugin/installer.rb
@@ -16,13 +16,15 @@ module Bundler
 
         version = options[:version] || [">= 0"]
 
-        if options[:git]
-          install_git(names, version, options)
-        elsif options[:local_git]
-          install_local_git(names, version, options)
-        else
-          sources = options[:source] || Bundler.rubygems.sources
-          install_rubygems(names, version, sources)
+        Bundler.settings.temporary(:disable_multisource => false) do
+          if options[:git]
+            install_git(names, version, options)
+          elsif options[:local_git]
+            install_local_git(names, version, options)
+          else
+            sources = options[:source] || Bundler.rubygems.sources
+            install_rubygems(names, version, sources)
+          end
         end
       end
 
@@ -82,7 +84,6 @@ module Bundler
         deps = names.map {|name| Dependency.new name, version }
 
         definition = Definition.new(nil, deps, source_list, true)
-        definition.allow_multisource!
         install_definition(definition)
       end
 
diff --git a/lib/bundler/resolver.rb b/lib/bundler/resolver.rb
index 0c11c83b72..585b8667ad 100644
--- a/lib/bundler/resolver.rb
+++ b/lib/bundler/resolver.rb
@@ -17,14 +17,15 @@ module Bundler
     # ==== Returns
     # <GemBundle>,nil:: If the list of dependencies can be resolved, a
     #   collection of gemspecs is returned. Otherwise, nil is returned.
-    def self.resolve(requirements, source_requirements = {}, base = [], gem_version_promoter = GemVersionPromoter.new, additional_base_requirements = [], platforms = nil)
+    def self.resolve(requirements, index, source_requirements = {}, base = [], gem_version_promoter = GemVersionPromoter.new, additional_base_requirements = [], platforms = nil)
       base = SpecSet.new(base) unless base.is_a?(SpecSet)
-      resolver = new(source_requirements, base, gem_version_promoter, additional_base_requirements, platforms)
+      resolver = new(index, source_requirements, base, gem_version_promoter, additional_base_requirements, platforms)
       result = resolver.start(requirements)
       SpecSet.new(result)
     end
 
-    def initialize(source_requirements, base, gem_version_promoter, additional_base_requirements, platforms)
+    def initialize(index, source_requirements, base, gem_version_promoter, additional_base_requirements, platforms)
+      @index = index
       @source_requirements = source_requirements
       @base = base
       @resolver = Molinillo::Resolver.new(self, self)
@@ -39,7 +40,7 @@ module Bundler
       @resolving_only_for_ruby = platforms == [Gem::Platform::RUBY]
       @gem_version_promoter = gem_version_promoter
       @use_gvp = Bundler.feature_flag.use_gem_version_promoter_for_major_updates? || !@gem_version_promoter.major?
-      @no_aggregate_global_source = @source_requirements[:global].nil?
+      @lockfile_uses_separate_rubygems_sources = Bundler.feature_flag.disable_multisource?
 
       @variant_specific_names = []
       @generic_names = ["Ruby\0", "RubyGems\0"]
@@ -124,7 +125,8 @@ module Bundler
       dependency = dependency_proxy.dep
       name = dependency.name
       search_result = @search_for[dependency_proxy] ||= begin
-        results = results_for(dependency, @base[name])
+        index = index_for(dependency)
+        results = index.search(dependency, @base[name])
 
         if vertex = @base_dg.vertex_named(name)
           locked_requirement = vertex.payload.requirement
@@ -193,26 +195,23 @@ module Bundler
       search_result
     end
 
-    def index_for(dependency, base)
+    def index_for(dependency)
       source = @source_requirements[dependency.name]
       if source
         source.specs
-      elsif @no_aggregate_global_source
-        dependency.all_sources.find(-> { Index.new }) do |s|
-          idx = s.specs
-          results = idx.search(dependency, base)
-          next if results.empty? || results == base
-          return idx
+      elsif @lockfile_uses_separate_rubygems_sources
+        Index.build do |idx|
+          if dependency.all_sources
+            dependency.all_sources.each {|s| idx.add_source(s.specs) if s }
+          else
+            idx.add_source @source_requirements[:default].specs
+          end
         end
       else
-        @source_requirements[:global]
+        @index
       end
     end
 
-    def results_for(dependency, base)
-      index_for(dependency, base).search(dependency, base)
-    end
-
     def name_for(dependency)
       dependency.name
     end
@@ -239,13 +238,11 @@ module Bundler
 
     def relevant_sources_for_vertex(vertex)
       if vertex.root?
-        [@source_requirements[vertex.name]].compact
-      elsif @no_aggregate_global_source
+        [@source_requirements[vertex.name]]
+      elsif @lockfile_uses_separate_rubygems_sources
         vertex.recursive_predecessors.map do |v|
           @source_requirements[v.name]
-        end.compact << @source_requirements[:default]
-      else
-        []
+        end << @source_requirements[:default]
       end
     end
 
@@ -286,7 +283,7 @@ module Bundler
         if (base = @base[dependency.name]) && !base.empty?
           dependency.requirement.satisfied_by?(base.first.version) ? 0 : 1
         else
-          all = index_for(dependency, base).search(dependency.name).size
+          all = index_for(dependency).search(dependency.name).size
 
           if all <= 1
             all - 1_000_000
@@ -329,7 +326,7 @@ module Bundler
             "The source does not contain any versions of '#{name}'"
           end
         else
-          message = "Could not find gem '#{SharedHelpers.pretty_dependency(requirement)}' in any of the gem sources " \
+          message = "Could not find gem '#{requirement}' in any of the gem sources " \
             "listed in your Gemfile#{cache_message}."
         end
         raise GemNotFound, message
@@ -414,8 +411,14 @@ module Bundler
 
             relevant_sources = if conflict.requirement.source
               [conflict.requirement.source]
-            else
+            elsif conflict.requirement.all_sources
               conflict.requirement.all_sources
+            elsif @lockfile_uses_separate_rubygems_sources
+              # every conflict should have an explicit group of sources when we
+              # enforce strict pinning
+              raise "no source set for #{conflict}"
+            else
+              []
             end.compact.map(&:to_s).uniq.sort
 
             metadata_requirement = name.end_with?("\0")
@@ -452,8 +455,7 @@ module Bundler
     def validate_resolved_specs!(resolved_specs)
       resolved_specs.each do |v|
         name = v.name
-        sources = relevant_sources_for_vertex(v)
-        next unless sources.any?
+        next unless sources = relevant_sources_for_vertex(v)
         sources.compact!
         if default_index = sources.index(@source_requirements[:default])
           sources.delete_at(default_index)
@@ -462,12 +464,14 @@ module Bundler
         sources.uniq!
         next if sources.size <= 1
 
+        multisource_disabled = Bundler.feature_flag.disable_multisource?
+
         msg = ["The gem '#{name}' was found in multiple relevant sources."]
         msg.concat sources.map {|s| "  * #{s}" }.sort
-        msg << "You #{@no_aggregate_global_source ? :must : :should} add this gem to the source block for the source you wish it to be installed from."
+        msg << "You #{multisource_disabled ? :must : :should} add this gem to the source block for the source you wish it to be installed from."
         msg = msg.join("\n")
 
-        raise SecurityError, msg if @no_aggregate_global_source
+        raise SecurityError, msg if multisource_disabled
         Bundler.ui.warn "Warning: #{msg}"
       end
     end
diff --git a/lib/bundler/settings.rb b/lib/bundler/settings.rb
index ceb2fde32c..749e4eb60e 100644
--- a/lib/bundler/settings.rb
+++ b/lib/bundler/settings.rb
@@ -20,6 +20,7 @@ module Bundler
       disable_exec_load
       disable_local_branch_check
       disable_local_revision_check
+      disable_multisource
       disable_shared_gems
       disable_version_check
       force_ruby_platform
diff --git a/lib/bundler/source/rubygems.rb b/lib/bundler/source/rubygems.rb
index 1b4bccadb8..5b89b1645d 100644
--- a/lib/bundler/source/rubygems.rb
+++ b/lib/bundler/source/rubygems.rb
@@ -21,7 +21,6 @@ module Bundler
         @allow_remote = false
         @allow_cached = false
         @caches = [cache_path, *Bundler.rubygems.gem_cache]
-        @disable_multisource = true
 
         Array(options["remotes"] || []).reverse_each {|r| add_remote(r) }
       end
@@ -50,16 +49,8 @@ module Bundler
         o.is_a?(Rubygems) && (o.credless_remotes - credless_remotes).empty?
       end
 
-      def disable_multisource?
-        @disable_multisource
-      end
-
-      def allow_multisource!
-        @disable_multisource = false
-      end
-
       def can_lock?(spec)
-        return super if disable_multisource?
+        return super if Bundler.feature_flag.disable_multisource?
         spec.source.is_a?(Rubygems)
       end
 
diff --git a/lib/bundler/source_list.rb b/lib/bundler/source_list.rb
index 4ba6415448..436891256d 100644
--- a/lib/bundler/source_list.rb
+++ b/lib/bundler/source_list.rb
@@ -5,41 +5,24 @@ module Bundler
     attr_reader :path_sources,
       :git_sources,
       :plugin_sources,
-      :global_path_source,
-      :metadata_source,
-      :disable_multisource
-
-    def global_rubygems_source
-      @global_rubygems_source ||= rubygems_aggregate_class.new
-    end
+      :global_rubygems_source,
+      :metadata_source
 
     def initialize
       @path_sources           = []
       @git_sources            = []
       @plugin_sources         = []
       @global_rubygems_source = nil
-      @global_path_source     = nil
+      @rubygems_aggregate     = rubygems_aggregate_class.new
       @rubygems_sources       = []
       @metadata_source        = Source::Metadata.new
-      @disable_multisource    = true
-    end
-
-    def disable_multisource?
-      @disable_multisource
-    end
-
-    def allow_multisource!
-      rubygems_sources.map(&:allow_multisource!)
-      @disable_multisource = false
     end
 
     def add_path_source(options = {})
       if options["gemspec"]
         add_source_to_list Source::Gemspec.new(options), path_sources
       else
-        path_source = add_source_to_list Source::Path.new(options), path_sources
-        @global_path_source ||= path_source if options["global"]
-        path_source
+        add_source_to_list Source::Path.new(options), path_sources
       end
     end
 
@@ -58,20 +41,24 @@ module Bundler
     end
 
     def global_rubygems_source=(uri)
-      @global_rubygems_source ||= rubygems_aggregate_class.new("remotes" => uri)
+      if Bundler.feature_flag.disable_multisource?
+        @global_rubygems_source ||= rubygems_aggregate_class.new("remotes" => uri)
+      end
+      add_rubygems_remote(uri)
     end
 
     def add_rubygems_remote(uri)
-      global_rubygems_source.add_remote(uri)
-      global_rubygems_source
+      return if Bundler.feature_flag.disable_multisource?
+      @rubygems_aggregate.add_remote(uri)
+      @rubygems_aggregate
     end
 
     def default_source
-      global_path_source || global_rubygems_source
+      global_rubygems_source || @rubygems_aggregate
     end
 
     def rubygems_sources
-      @rubygems_sources + [global_rubygems_source]
+      @rubygems_sources + [default_source]
     end
 
     def rubygems_remotes
@@ -88,7 +75,7 @@ module Bundler
 
     def lock_sources
       lock_sources = (path_sources + git_sources + plugin_sources).sort_by(&:to_s)
-      if disable_multisource?
+      if Bundler.feature_flag.disable_multisource?
         lock_sources + rubygems_sources.sort_by(&:to_s)
       else
         lock_sources << combine_rubygems_sources
@@ -105,9 +92,9 @@ module Bundler
         end
       end
 
-      replacement_rubygems = !disable_multisource? &&
+      replacement_rubygems = !Bundler.feature_flag.disable_multisource? &&
         replacement_sources.detect {|s| s.is_a?(Source::Rubygems) }
-      @global_rubygems_source = replacement_rubygems if replacement_rubygems
+      @rubygems_aggregate = replacement_rubygems if replacement_rubygems
 
       return true if !equal_sources?(lock_sources, replacement_sources) && !equivalent_sources?(lock_sources, replacement_sources)
       return true if replacement_rubygems && rubygems_remotes.sort_by(&:to_s) != replacement_rubygems.remotes.sort_by(&:to_s)
@@ -123,6 +110,10 @@ module Bundler
       all_sources.each(&:remote!)
     end
 
+    def rubygems_primary_remotes
+      @rubygems_aggregate.remotes
+    end
+
     private
 
     def rubygems_aggregate_class
@@ -145,9 +136,7 @@ module Bundler
     end
 
     def combine_rubygems_sources
-      aggregate_source = Source::Rubygems.new("remotes" => rubygems_remotes)
-      aggregate_source.allow_multisource! unless disable_multisource?
-      aggregate_source
+      Source::Rubygems.new("remotes" => rubygems_remotes)
     end
 
     def warn_on_git_protocol(source)
diff --git a/lib/bundler/version.rb b/lib/bundler/version.rb
index 0ddfa668cd..64c46ddb25 100644
--- a/lib/bundler/version.rb
+++ b/lib/bundler/version.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: false
 
 module Bundler
-  VERSION = "2.2.10".freeze
+  VERSION = "2.2.11".freeze
 
   def self.bundler_major_version
     @bundler_major_version ||= VERSION.split(".").first.to_i
diff --git a/lib/rubygems.rb b/lib/rubygems.rb
index 22fe0366b2..d5f6356822 100644
--- a/lib/rubygems.rb
+++ b/lib/rubygems.rb
@@ -8,7 +8,7 @@
 require 'rbconfig'
 
 module Gem
-  VERSION = "3.2.10".freeze
+  VERSION = "3.2.11".freeze
 end
 
 # Must be first since it unloads the prelude from 1.9.2
diff --git a/lib/rubygems/config_file.rb b/lib/rubygems/config_file.rb
index 854d09ef3d..9dc41a2995 100644
--- a/lib/rubygems/config_file.rb
+++ b/lib/rubygems/config_file.rb
@@ -45,6 +45,7 @@ class Gem::ConfigFile
   DEFAULT_UPDATE_SOURCES = true
   DEFAULT_CONCURRENT_DOWNLOADS = 8
   DEFAULT_CERT_EXPIRATION_LENGTH_DAYS = 365
+  DEFAULT_IPV4_FALLBACK_ENABLED = false
 
   ##
   # For Ruby packagers to set configuration defaults.  Set in
@@ -141,6 +142,12 @@ class Gem::ConfigFile
   attr_accessor :cert_expiration_length_days
 
   ##
+  # == Experimental ==
+  # Fallback to IPv4 when IPv6 is not reachable or slow (default: false)
+
+  attr_accessor :ipv4_fallback_enabled
+
+  ##
   # Path name of directory or file of openssl client certificate, used for remote https connection with client authentication
 
   attr_reader :ssl_client_cert
@@ -175,6 +182,7 @@ class Gem::ConfigFile
     @update_sources = DEFAULT_UPDATE_SOURCES
     @concurrent_downloads = DEFAULT_CONCURRENT_DOWNLOADS
     @cert_expiration_length_days = DEFAULT_CERT_EXPIRATION_LENGTH_DAYS
+    @ipv4_fallback_enabled = ENV['IPV4_FALLBACK_ENABLED'] == 'true' || DEFAULT_IPV4_FALLBACK_ENABLED
 
     operating_system_config = Marshal.load Marshal.dump(OPERATING_SYSTEM_DEFAULTS)
     platform_config = Marshal.load Marshal.dump(PLATFORM_DEFAULTS)
@@ -203,6 +211,7 @@ class Gem::ConfigFile
     @disable_default_gem_server  = @hash[:disable_default_gem_server]  if @hash.key? :disable_default_gem_server
     @sources                     = @hash[:sources]                     if @hash.key? :sources
     @cert_expiration_length_days = @hash[:cert_expiration_length_days] if @hash.key? :cert_expiration_length_days
+    @ipv4_fallback_enabled       = @hash[:ipv4_fallback_enabled]       if @hash.key? :ipv4_fallback_enabled
 
     @ssl_verify_mode  = @hash[:ssl_verify_mode]  if @hash.key? :ssl_verify_mode
     @ssl_ca_cert      = @hash[:ssl_ca_cert]      if @hash.key? :ssl_ca_cert
diff --git a/lib/rubygems/core_ext/tcpsocket_init.rb b/lib/rubygems/core_ext/tcpsocket_init.rb
new file mode 100644
index 0000000000..3275c58112
--- /dev/null
+++ b/lib/rubygems/core_ext/tcpsocket_init.rb
@@ -0,0 +1,49 @@
+require 'socket'
+
+module CoreExtensions
+  module TCPSocketExt
+    def self.prepended(base)
+      base.prepend Initializer
+    end
+
+    module Initializer
+      CONNECTION_TIMEOUT = 5
+      IPV4_DELAY_SECONDS = 0.1
+
+      def initialize(host, serv, *rest)
+        mutex = Mutex.new
+        addrs = []
+        cond_var = ConditionVariable.new
+
+        Addrinfo.foreach(host, serv, nil, :STREAM) do |addr|
+          Thread.report_on_exception = false if defined? Thread.report_on_exception = ()
+
+          Thread.new(addr) do
+            # give head start to ipv6 addresses
+            sleep IPV4_DELAY_SECONDS if addr.ipv4?
+
+            # raises Errno::ECONNREFUSED when ip:port is unreachable
+            Socket.tcp(addr.ip_address, serv, connect_timeout: CONNECTION_TIMEOUT).close
+            mutex.synchronize do
+              addrs << addr.ip_address
+              cond_var.signal
+            end
+          end
+        end
+
+        mutex.synchronize do
+          timeout_time = CONNECTION_TIMEOUT + Time.now.to_f
+          while addrs.empty? && (remaining_time = timeout_time - Time.now.to_f) > 0
+            cond_var.wait(mutex, remaining_time)
+          end
+
+          host = addrs.shift unless addrs.empty?
+        end
+
+        super(host, serv, *rest)
+      end
+    end
+  end
+end
+
+TCPSocket.prepend CoreExtensions::TCPSocketExt
diff --git a/lib/rubygems/remote_fetcher.rb b/lib/rubygems/remote_fetcher.rb
index 53e840978c..7ac334d30d 100644
--- a/lib/rubygems/remote_fetcher.rb
+++ b/lib/rubygems/remote_fetcher.rb
@@ -78,6 +78,7 @@ class Gem::RemoteFetcher
   #            fetching the gem.
 
   def initialize(proxy=nil, dns=nil, headers={})
+    require 'rubygems/core_ext/tcpsocket_init' if Gem.configuration.ipv4_fallback_enabled
     require 'net/http'
     require 'stringio'
     require 'uri'
diff --git a/spec/bundler/bundler/dsl_spec.rb b/spec/bundler/bundler/dsl_spec.rb
index a47dd6e399..ff87b57886 100644
--- a/spec/bundler/bundler/dsl_spec.rb
+++ b/spec/bundler/bundler/dsl_spec.rb
@@ -25,7 +25,7 @@ RSpec.describe Bundler::Dsl do
       expect { subject.git_source(:example) }.to raise_error(Bundler::InvalidOption)
     end
 
-    context "default hosts", :bundler => "< 3" do
+    context "default hosts", :bundler => "2" do
       it "converts :github to URI using https" do
         subject.gem("sparks", :github => "indirect/sparks")
         github_uri = "https://github.com/indirect/sparks.git"
@@ -195,6 +195,19 @@ RSpec.describe Bundler::Dsl do
     #   gem 'spree_api'
     #   gem 'spree_backend'
     # end
+    describe "#github", :bundler => "< 3" do
+      it "from github" do
+        spree_gems = %w[spree_core spree_api spree_backend]
+        subject.github "spree" do
+          spree_gems.each {|spree_gem| subject.send :gem, spree_gem }
+        end
+
+        subject.dependencies.each do |d|
+          expect(d.source.uri).to eq("https://github.com/spree/spree.git")
+        end
+      end
+    end
+
     describe "#github" do
       it "from github" do
         spree_gems = %w[spree_core spree_api spree_backend]
diff --git a/spec/bundler/bundler/plugin_spec.rb b/spec/bundler/bundler/plugin_spec.rb
index d18896895e..8c95723bcc 100644
--- a/spec/bundler/bundler/plugin_spec.rb
+++ b/spec/bundler/bundler/plugin_spec.rb
@@ -112,7 +112,6 @@ RSpec.describe Bundler::Plugin do
     before do
       allow(Plugin::DSL).to receive(:new) { builder }
       allow(builder).to receive(:eval_gemfile).with(gemfile)
-      allow(builder).to receive(:check_primary_source_safety)
       allow(builder).to receive(:to_definition) { definition }
       allow(builder).to receive(:inferred_plugins) { [] }
     end
diff --git a/spec/bundler/bundler/source_list_spec.rb b/spec/bundler/bundler/source_list_spec.rb
index 0c40ba8a77..3a0691b959 100644
--- a/spec/bundler/bundler/source_list_spec.rb
+++ b/spec/bundler/bundler/source_list_spec.rb
@@ -372,7 +372,26 @@ RSpec.describe Bundler::SourceList do
       source_list.add_git_source("uri" => "git://first-git.org/path.git")
     end
 
-    it "returns all sources, without combining rubygems sources" do
+    it "combines the rubygems sources into a single instance, removing duplicate remotes from the end", :bundler => "< 3" do
+      expect(source_list.lock_sources).to eq [
+        Bundler::Source::Git.new("uri" => "git://first-git.org/path.git"),
+        Bundler::Source::Git.new("uri" => "git://second-git.org/path.git"),
+        Bundler::Source::Git.new("uri" => "git://third-git.org/path.git"),
+        ASourcePlugin.new("uri" => "https://second-plugin.org/random"),
+        ASourcePlugin.new("uri" => "https://third-bar.org/foo"),
+        Bundler::Source::Path.new("path" => "/first/path/to/gem"),
+        Bundler::Source::Path.new("path" => "/second/path/to/gem"),
+        Bundler::Source::Path.new("path" => "/third/path/to/gem"),
+        Bundler::Source::Rubygems.new("remotes" => [
+          "https://duplicate-rubygems.org",
+          "https://first-rubygems.org",
+          "https://second-rubygems.org",
+          "https://third-rubygems.org",
+        ]),
+      ]
+    end
+
+    it "returns all sources, without combining rubygems sources", :bundler => "3" do
       expect(source_list.lock_sources).to eq [
         Bundler::Source::Git.new("uri" => "git://first-git.org/path.git"),
         Bundler::Source::Git.new("uri" => "git://second-git.org/path.git"),
diff --git a/spec/bundler/commands/exec_spec.rb b/spec/bundler/commands/exec_spec.rb
index bb4091ef98..5d43586116 100644
--- a/spec/bundler/commands/exec_spec.rb
+++ b/spec/bundler/commands/exec_spec.rb
@@ -762,8 +762,7 @@ RSpec.describe "bundle exec" do
       let(:exit_code) { Bundler::GemNotFound.new.status_code }
       let(:expected) { "" }
       let(:expected_err) { <<-EOS.strip }
-\e[31mCould not find gem 'rack (= 2)' in locally installed gems.
-The source contains the following versions of 'rack': 0.9.1, 1.0.0\e[0m
+\e[31mCould not find gem 'rack (= 2)' in any of the gem sources listed in your Gemfile.\e[0m
 \e[33mRun `bundle install` to install missing gems.\e[0m
       EOS
 
diff --git a/spec/bundler/commands/post_bundle_message_spec.rb b/spec/bundler/commands/post_bundle_message_spec.rb
index 3f81808980..2c965f0ddd 100644
--- a/spec/bundler/commands/post_bundle_message_spec.rb
+++ b/spec/bundler/commands/post_bundle_message_spec.rb
@@ -113,7 +113,16 @@ RSpec.describe "post bundle message" do
         bundle "config set force_ruby_platform true"
       end
 
-      it "should report a helpful error message" do
+      it "should report a helpful error message", :bundler => "< 3" do
+        install_gemfile <<-G, :raise_on_error => false
+          source "#{file_uri_for(gem_repo1)}"
+          gem "rack"
+          gem "not-a-gem", :group => :development
+        G
+        expect(err).to include("Could not find gem 'not-a-gem' in any of the gem sources listed in your Gemfile.")
+      end
+
+      it "should report a helpful error message", :bundler => "3" do
         install_gemfile <<-G, :raise_on_error => false
           source "#{file_uri_for(gem_repo1)}"
           gem "rack"
diff --git a/spec/bundler/install/gemfile/gemspec_spec.rb b/spec/bundler/install/gemfile/gemspec_spec.rb
index 4001df26da..7a95a8abde 100644
--- a/spec/bundler/install/gemfile/gemspec_spec.rb
+++ b/spec/bundler/install/gemfile/gemspec_spec.rb
@@ -422,13 +422,14 @@ RSpec.describe "bundle install from an existing gemspec" do
           end
         end
 
-        gemfile <<-G
-          source "#{file_uri_for(gem_repo2)}"
-          gemspec
-        G
-
-        simulate_platform("ruby") { bundle "install" }
-        simulate_platform("jruby") { bundle "install" }
+        %w[ruby jruby].each do |platform|
+          simulate_platform(platform) do
+            install_gemfile <<-G
+              source "#{file_uri_for(gem_repo2)}"
+              gemspec
+            G
+          end
+        end
       end
 
       context "on ruby" do
diff --git a/spec/bundler/install/gemfile/sources_spec.rb b/spec/bundler/install/gemfile/sources_spec.rb
index e40ae84c59..655f91dd69 100644
--- a/spec/bundler/install/gemfile/sources_spec.rb
+++ b/spec/bundler/install/gemfile/sources_spec.rb
@@ -27,7 +27,7 @@ RSpec.describe "bundle install with gems on multiple sources" do
         G
       end
 
-      it "warns about ambiguous gems, but installs anyway, prioritizing sources last to first", :bundler => "< 3" do
+      it "warns about ambiguous gems, but installs anyway, prioritizing sources last to first", :bundler => "2" do
         bundle :install
 
         expect(err).to include("Warning: the gem 'rack' was found in multiple sources.")
@@ -54,7 +54,7 @@ RSpec.describe "bundle install with gems on multiple sources" do
         G
       end
 
-      it "warns about ambiguous gems, but installs anyway", :bundler => "< 3" do
+      it "warns about ambiguous gems, but installs anyway", :bundler => "2" do
         bundle :install
         expect(err).to include("Warning: the gem 'rack' was found in multiple sources.")
         expect(err).to include("Installed from: #{file_uri_for(gem_repo1)}")
@@ -96,7 +96,7 @@ RSpec.describe "bundle install with gems on multiple sources" do
 
       it "installs the gems without any warning" do
         bundle :install
-        expect(err).not_to include("Warning")
+        expect(out).not_to include("Warning")
         expect(the_bundle).to include_gems("rack-obama 1.0.0")
         expect(the_bundle).to include_gems("rack 1.0.0", :source => "remote1")
       end
@@ -128,7 +128,7 @@ RSpec.describe "bundle install with gems on multiple sources" do
           end
         end
 
-        install_gemfile <<-G
+        gemfile <<-G
           source "#{file_uri_for(gem_repo3)}"
           gem "rack-obama" # should come from repo3!
           gem "rack", :source => "#{file_uri_for(gem_repo1)}"
@@ -136,7 +136,8 @@ RSpec.describe "bundle install with gems on multiple sources" do
       end
 
       it "installs the gems without any warning" do
-        expect(err).not_to include("Warning")
+        bundle :install
+        expect(out).not_to include("Warning")
         expect(the_bundle).to include_gems("rack-obama 1.0.0", "rack 1.0.0")
       end
     end
@@ -172,8 +173,8 @@ RSpec.describe "bundle install with gems on multiple sources" do
 
           it "installs from the same source without any warning" do
             bundle :install
-            expect(err).not_to include("Warning")
-            expect(the_bundle).to include_gems("depends_on_rack 1.0.1", "rack 1.0.0", :source => "remote3")
+            expect(out).not_to include("Warning")
+            expect(the_bundle).to include_gems("depends_on_rack 1.0.1", "rack 1.0.0")
           end
         end
 
@@ -187,38 +188,27 @@ RSpec.describe "bundle install with gems on multiple sources" do
             end
           end
 
-          it "installs from the same source without any warning" do
-            bundle :install
+          context "when disable_multisource is set" do
+            before do
+              bundle "config set disable_multisource true"
+            end
 
-            expect(err).not_to include("Warning: the gem 'rack' was found in multiple sources.")
-            expect(the_bundle).to include_gems("depends_on_rack 1.0.1", "rack 1.0.0", :source => "remote3")
+            it "installs from the same source without any warning" do
+              bundle :install
 
-            # In https://github.com/bundler/bundler/issues/3585 this failed
-            # when there is already a lock file, and the gems are missing, so try again
-            system_gems []
-            bundle :install
+              expect(out).not_to include("Warning: the gem 'rack' was found in multiple sources.")
+              expect(err).not_to include("Warning: the gem 'rack' was found in multiple sources.")
+              expect(the_bundle).to include_gems("depends_on_rack 1.0.1", "rack 1.0.0")
 
-            expect(err).not_to include("Warning: the gem 'rack' was found in multiple sources.")
-            expect(the_bundle).to include_gems("depends_on_rack 1.0.1", "rack 1.0.0", :source => "remote3")
-          end
-        end
+              # when there is already a lock file, and the gems are missing, so try again
+              system_gems []
+              bundle :install
 
-        context "and in another source with a higher version" do
-          before do
-            # need this to be broken to check for correct source ordering
-            build_repo gem_repo2 do
-              build_gem "rack", "1.0.1" do |s|
-                s.write "lib/rack.rb", "RACK = 'FAIL'"
-              end
+              expect(out).not_to include("Warning: the gem 'rack' was found in multiple sources.")
+              expect(err).not_to include("Warning: the gem 'rack' was found in multiple sources.")
+              expect(the_bundle).to include_gems("depends_on_rack 1.0.1", "rack 1.0.0")
             end
           end
-
-          it "installs from the same source without any warning" do
-            bundle :install
-
-            expect(err).not_to include("Warning: the gem 'rack' was found in multiple sources.")
-            expect(the_bundle).to include_gems("depends_on_rack 1.0.1", "rack 1.0.0", :source => "remote3")
-          end
         end
       end
 
@@ -232,7 +222,7 @@ RSpec.describe "bundle install with gems on multiple sources" do
 
         context "and not in any other sources" do
           before do
-            install_gemfile <<-G
+            gemfile <<-G
               source "#{file_uri_for(gem_repo2)}"
               source "#{file_uri_for(gem_repo3)}" do
                 gem "depends_on_rack"
@@ -241,7 +231,8 @@ RSpec.describe "bundle install with gems on multiple sources" do
           end
 
           it "installs from the other source without any warning" do
-            expect(err).not_to include("Warning")
+            bundle :install
+            expect(out).not_to include("Warning")
             expect(the_bundle).to include_gems("depends_on_rack 1.0.1", "rack 1.0.0")
           end
         end
@@ -257,7 +248,7 @@ RSpec.describe "bundle install with gems on multiple sources" do
             G
           end
 
-          it "installs from the other source and warns about ambiguous gems", :bundler => "< 3" do
+          it "installs from the other source and warns about ambiguous gems", :bundler => "2" do
             bundle :install
             expect(err).to include("Warning: the gem 'rack' was found in multiple sources.")
             expect(err).to include("Installed from: #{file_uri_for(gem_repo2)}")
@@ -289,7 +280,7 @@ RSpec.describe "bundle install with gems on multiple sources" do
             G
           end
 
-          it "installs the dependency from the pinned source without warning", :bundler => "< 3" do
+          it "installs the dependency from the pinned source without warning", :bundler => "2" do
             bundle :install
 
             expect(err).not_to include("Warning: the gem 'rack' was found in multiple sources.")
@@ -314,74 +305,80 @@ RSpec.describe "bundle install with gems on multiple sources" do
     end
 
     context "when a top-level gem has an indirect dependency" do
-      before do
-        build_repo gem_repo2 do
-          build_gem "depends_on_rack", "1.0.1" do |s|
-            s.add_dependency "rack"
-          end
+      context "when disable_multisource is set" do
+        before do
+          bundle "config set disable_multisource true"
         end
 
-        build_repo gem_repo3 do
-          build_gem "unrelated_gem", "1.0.0"
-        end
+        before do
+          build_repo gem_repo2 do
+            build_gem "depends_on_rack", "1.0.1" do |s|
+              s.add_dependency "rack"
+            end
+          end
 
-        gemfile <<-G
-          source "#{file_uri_for(gem_repo2)}"
+          build_repo gem_repo3 do
+            build_gem "unrelated_gem", "1.0.0"
+          end
 
-          gem "depends_on_rack"
+          gemfile <<-G
+            source "#{file_uri_for(gem_repo2)}"
 
-          source "#{file_uri_for(gem_repo3)}" do
-            gem "unrelated_gem"
-          end
-        G
-      end
+            gem "depends_on_rack"
 
-      context "and the dependency is only in the top-level source" do
-        before do
-          update_repo gem_repo2 do
-            build_gem "rack", "1.0.0"
-          end
+            source "#{file_uri_for(gem_repo3)}" do
+              gem "unrelated_gem"
+            end
+          G
         end
 
-        it "installs all gems without warning" do
-          bundle :install
-          expect(err).not_to include("Warning")
-          expect(the_bundle).to include_gems("depends_on_rack 1.0.1", "rack 1.0.0", "unrelated_gem 1.0.0")
+        context "and the dependency is only in the top-level source" do
+          before do
+            update_repo gem_repo2 do
+              build_gem "rack", "1.0.0"
+            end
+          end
+
+          it "installs all gems without warning" do
+            bundle :install
+            expect(err).not_to include("Warning")
+            expect(the_bundle).to include_gems("depends_on_rack 1.0.1", "rack 1.0.0", "unrelated_gem 1.0.0")
+          end
         end
-      end
 
-      context "and the dependency is only in a pinned source" do
-        before do
-          update_repo gem_repo3 do
-            build_gem "rack", "1.0.0" do |s|
-              s.write "lib/rack.rb", "RACK = 'FAIL'"
+        context "and the dependency is only in a pinned source" do
+          before do
+            update_repo gem_repo3 do
+              build_gem "rack", "1.0.0" do |s|
+                s.write "lib/rack.rb", "RACK = 'FAIL'"
+              end
             end
           end
-        end
 
-        it "does not find the dependency" do
-          bundle :install, :raise_on_error => false
-          expect(err).to include("Could not find gem 'rack', which is required by gem 'depends_on_rack', in any of the relevant sources")
+          it "does not find the dependency" do
+            bundle :install, :raise_on_error => false
+            expect(err).to include("Could not find gem 'rack', which is required by gem 'depends_on_rack', in any of the relevant sources")
+          end
         end
-      end
 
-      context "and the dependency is in both the top-level and a pinned source" do
-        before do
-          update_repo gem_repo2 do
-            build_gem "rack", "1.0.0"
-          end
+        context "and the dependency is in both the top-level and a pinned source" do
+          before do
+            update_repo gem_repo2 do
+              build_gem "rack", "1.0.0"
+            end
 
-          update_repo gem_repo3 do
-            build_gem "rack", "1.0.0" do |s|
-              s.write "lib/rack.rb", "RACK = 'FAIL'"
+            update_repo gem_repo3 do
+              build_gem "rack", "1.0.0" do |s|
+                s.write "lib/rack.rb", "RACK = 'FAIL'"
+              end
             end
           end
-        end
 
-        it "installs the dependency from the top-level source without warning" do
-          bundle :install
-          expect(err).not_to include("Warning")
-          expect(the_bundle).to include_gems("depends_on_rack 1.0.1", "rack 1.0.0", "unrelated_gem 1.0.0")
+          it "installs the dependency from the top-level source without warning" do
+            bundle :install
+            expect(err).not_to include("Warning")
+            expect(the_bundle).to include_gems("depends_on_rack 1.0.1", "rack 1.0.0", "unrelated_gem 1.0.0")
+          end
         end
       end
     end
@@ -392,14 +389,15 @@ RSpec.describe "bundle install with gems on multiple sources" do
           build_gem "not_in_repo1", "1.0.0"
         end
 
-        install_gemfile <<-G, :raise_on_error => false
+        gemfile <<-G
           source "#{file_uri_for(gem_repo3)}"
           gem "not_in_repo1", :source => "#{file_uri_for(gem_repo1)}"
         G
       end
 
       it "does not install the gem" do
-        expect(err).to include("Could not find gem 'not_in_repo1")
+        bundle :install, :raise_on_error => false
+        expect(err).to include("Could not find gem 'not_in_repo1'")
       end
     end
 
@@ -435,92 +433,6 @@ RSpec.describe "bundle install with gems on multiple sources" do
       end
     end
 
-    context "with a lockfile with aggregated rubygems sources" do
-      let(:aggregate_gem_section_lockfile) do
-        <<~L
-          GEM
-            remote: #{file_uri_for(gem_repo1)}/
-            remote: #{file_uri_for(gem_repo3)}/
-            specs:
-              rack (0.9.1)
-
-          PLATFORMS
-            #{specific_local_platform}
-
-          DEPENDENCIES
-            rack!
-
-          BUNDLED WITH
-             #{Bundler::VERSION}
-        L
-      end
-
-      let(:split_gem_section_lockfile) do
-        <<~L
-          GEM
-            remote: #{file_uri_for(gem_repo1)}/
-            specs:
-
-          GEM
-            remote: #{file_uri_for(gem_repo3)}/
-            specs:
-              rack (0.9.1)
-
-          PLATFORMS
-            #{specific_local_platform}
-
-          DEPENDENCIES
-            rack!
-
-          BUNDLED WITH
-             #{Bundler::VERSION}
-        L
-      end
-
-      before do
-        build_repo gem_repo3 do
-          build_gem "rack", "0.9.1"
-        end
-
-        gemfile <<-G
-          source "#{file_uri_for(gem_repo1)}"
-          source "#{file_uri_for(gem_repo3)}" do
-            gem 'rack'
-          end
-        G
-
-        lockfile aggregate_gem_section_lockfile
-      end
-
-      it "installs a lockfile with separate rubygems source sections if not in frozen mode" do
-        bundle "install"
-
-        expect(lockfile).to eq(split_gem_section_lockfile)
-
-        expect(the_bundle).to include_gems("rack 0.9.1", :source => "remote3")
-      end
-
-      it "installs the existing lockfile but prints a warning if in frozen mode", :bundler => "< 3" do
-        bundle "config set --local deployment true"
-
-        bundle "install"
-
-        expect(lockfile).to eq(aggregate_gem_section_lockfile)
-
-        expect(the_bundle).to include_gems("rack 0.9.1", :source => "remote3")
-      end
-
-      it "refuses to install the existing lockfile and prints an error if in frozen mode", :bundler => "3" do
-        bundle "config set --local deployment true"
-
-        bundle "install", :raise_on_error =>false
-
-        expect(lockfile).to eq(aggregate_gem_section_lockfile)
-        expect(err).to include("Your lockfile contains a single rubygems source section with multiple remotes, which is insecure.")
-        expect(out).to be_empty
-      end
-    end
-
     context "with a path gem in the same Gemfile" do
       before do
         build_lib "foo"
@@ -545,13 +457,14 @@ RSpec.describe "bundle install with gems on multiple sources" do
     before do
       system_gems "rack-0.9.1"
 
-      install_gemfile <<-G
+      gemfile <<-G
         source "#{file_uri_for(gem_repo1)}"
         gem "rack" # shoud come from repo1!
       G
     end
 
     it "installs the gems without any warning" do
+      bundle :install
       expect(err).not_to include("Warning")
       expect(the_bundle).to include_gems("rack 1.0.0")
     end
@@ -702,12 +615,16 @@ RSpec.describe "bundle install with gems on multiple sources" do
       G
     end
 
-    it "installs the higher version in the new repo" do
+    it "keeps the old version", :bundler => "2" do
+      expect(the_bundle).to include_gems("rack 1.0.0")
+    end
+
+    it "installs the higher version in the new repo", :bundler => "3" do
       expect(the_bundle).to include_gems("rack 1.2")
     end
   end
 
-  context "when a gem is available from multiple ambiguous sources" do
+  context "when a gem is available from multiple ambiguous sources", :bundler => "3" do
     it "raises, suggesting a source block" do
       build_repo4 do
         build_gem "depends_on_rack" do |s|
diff --git a/spec/bundler/install/gems/flex_spec.rb b/spec/bundler/install/gems/flex_spec.rb
index 326ec51214..7ab0ded26d 100644
--- a/spec/bundler/install/gems/flex_spec.rb
+++ b/spec/bundler/install/gems/flex_spec.rb
@@ -245,7 +245,37 @@ RSpec.describe "bundle flex_install" do
   end
 
   describe "when adding a new source" do
-    it "updates the lockfile" do
+    it "updates the lockfile", :bundler => "< 3" do
+      build_repo2
+      install_gemfile <<-G
+        source "#{file_uri_for(gem_repo1)}"
+        gem "rack"
+      G
+      install_gemfile <<-G
+        source "#{file_uri_for(gem_repo1)}"
+        source "#{file_uri_for(gem_repo2)}"
+        gem "rack"
+      G
+
+      lockfile_should_be <<-L
+      GEM
+        remote: #{file_uri_for(gem_repo1)}/
+        remote: #{file_uri_for(gem_repo2)}/
+        specs:
+          rack (1.0.0)
+
+      PLATFORMS
+        #{lockfile_platforms}
+
+      DEPENDENCIES
+        rack
+
+      BUNDLED WITH
+         #{Bundler::VERSION}
+      L
+    end
+
+    it "updates the lockfile", :bundler => "3" do
       build_repo2
       install_gemfile <<-G
         source "#{file_uri_for(gem_repo1)}"
diff --git a/spec/bundler/lock/lockfile_spec.rb b/spec/bundler/lock/lockfile_spec.rb
index 639ccb87ea..d3591cd62a 100644
--- a/spec/bundler/lock/lockfile_spec.rb
+++ b/spec/bundler/lock/lockfile_spec.rb
@@ -318,7 +318,40 @@ RSpec.describe "the lockfile format" do
     G
   end
 
-  it "generates a lockfile without credentials for a configured source" do
+  it "generates a lockfile without credentials for a configured source", :bundler => "< 3" do
+    bundle "config set http://localgemserver.test/ user:pass"
+
+    install_gemfile(<<-G, :artifice => "endpoint_strict_basic_authentication", :quiet => true)
+      source "http://localgemserver.test/" do
+
+      end
+
+      source "http://user:pass@othergemserver.test/" do
+        gem "rack-obama", ">= 1.0"
+      end
+    G
+
+    lockfile_should_be <<-G
+      GEM
+        remote: http://localgemserver.test/
+        remote: http://user:pass@othergemserver.test/
+        specs:
+          rack (1.0.0)
+          rack-obama (1.0)
+            rack
+
+      PLATFORMS
+        #{lockfile_platforms}
+
+      DEPENDENCIES
+        rack-obama (>= 1.0)!
+
+      BUNDLED WITH
+         #{Bundler::VERSION}
+    G
+  end
+
+  it "generates a lockfile without credentials for a configured source", :bundler => "3" do
     bundle "config set http://localgemserver.test/ user:pass"
 
     install_gemfile(<<-G, :artifice => "endpoint_strict_basic_authentication", :quiet => true)
diff --git a/spec/bundler/other/major_deprecation_spec.rb b/spec/bundler/other/major_deprecation_spec.rb
index cb85b6c9cb..d061ca7064 100644
--- a/spec/bundler/other/major_deprecation_spec.rb
+++ b/spec/bundler/other/major_deprecation_spec.rb
@@ -17,7 +17,7 @@ RSpec.describe "major deprecations" do
         bundle "exec ruby -e #{source.dump}"
       end
 
-      it "is deprecated in favor of .unbundled_env", :bundler => "< 3" do
+      it "is deprecated in favor of .unbundled_env", :bundler => "2" do
         expect(deprecations).to include \
           "`Bundler.clean_env` has been deprecated in favor of `Bundler.unbundled_env`. " \
           "If you instead want the environment before bundler was originally loaded, use `Bundler.original_env` " \
@@ -33,7 +33,7 @@ RSpec.describe "major deprecations" do
         bundle "exec ruby -e #{source.dump}"
       end
 
-      it "is deprecated in favor of .unbundled_env", :bundler => "< 3" do
+      it "is deprecated in favor of .unbundled_env", :bundler => "2" do
         expect(deprecations).to include(
           "`Bundler.with_clean_env` has been deprecated in favor of `Bundler.with_unbundled_env`. " \
           "If you instead want the environment before bundler was originally loaded, use `Bundler.with_original_env` " \
@@ -50,7 +50,7 @@ RSpec.describe "major deprecations" do
         bundle "exec ruby -e #{source.dump}"
       end
 
-      it "is deprecated in favor of .unbundled_system", :bundler => "< 3" do
+      it "is deprecated in favor of .unbundled_system", :bundler => "2" do
         expect(deprecations).to include(
           "`Bundler.clean_system` has been deprecated in favor of `Bundler.unbundled_system`. " \
           "If you instead want to run the command in the environment before bundler was originally loaded, use `Bundler.original_system` " \
@@ -67,7 +67,7 @@ RSpec.describe "major deprecations" do
         bundle "exec ruby -e #{source.dump}"
       end
 
-      it "is deprecated in favor of .unbundled_exec", :bundler => "< 3" do
+      it "is deprecated in favor of .unbundled_exec", :bundler => "2" do
         expect(deprecations).to include(
           "`Bundler.clean_exec` has been deprecated in favor of `Bundler.unbundled_exec`. " \
           "If you instead want to exec to a command in the environment before bundler was originally loaded, use `Bundler.original_exec` " \
@@ -84,7 +84,7 @@ RSpec.describe "major deprecations" do
         bundle "exec ruby -e #{source.dump}"
       end
 
-      it "is deprecated in favor of .load", :bundler => "< 3" do
+      it "is deprecated in favor of .load", :bundler => "2" do
         expect(deprecations).to include "Bundler.environment has been removed in favor of Bundler.load (called at -e:1)"
       end
 
@@ -109,7 +109,7 @@ RSpec.describe "major deprecations" do
       bundle "check --path vendor/bundle", :raise_on_error => false
     end
 
-    it "should print a deprecation warning", :bundler => "< 3" do
+    it "should print a deprecation warning", :bundler => "2" do
       expect(deprecations).to include(
         "The `--path` flag is deprecated because it relies on being " \
         "remembered across bundler invocations, which bundler will no " \
@@ -118,7 +118,7 @@ RSpec.describe "major deprecations" do
       )
     end
 
-    pending "fails with a helpful error", :bundler => "3"
+    pending "should fail with a helpful error", :bundler => "3"
   end
 
   context "bundle check --path=" do
@@ -131,7 +131,7 @@ RSpec.describe "major deprecations" do
       bundle "check --path=vendor/bundle", :raise_on_error => false
     end
 
-    it "should print a deprecation warning", :bundler => "< 3" do
+    it "should print a deprecation warning", :bundler => "2" do
       expect(deprecations).to include(
         "The `--path` flag is deprecated because it relies on being " \
         "remembered across bundler invocations, which bundler will no " \
@@ -140,7 +140,7 @@ RSpec.describe "major deprecations" do
       )
     end
 
-    pending "fails with a helpful error", :bundler => "3"
+    pending "should fail with a helpful error", :bundler => "3"
   end
 
   context "bundle cache --all" do
@@ -153,7 +153,7 @@ RSpec.describe "major deprecations" do
       bundle "cache --all", :raise_on_error => false
     end
 
-    it "should print a deprecation warning", :bundler => "< 3" do
+    it "should print a deprecation warning", :bundler => "2" do
       expect(deprecations).to include(
         "The `--all` flag is deprecated because it relies on being " \
         "remembered across bundler invocations, which bundler will no " \
@@ -162,7 +162,7 @@ RSpec.describe "major deprecations" do
       )
     end
 
-    pending "fails with a helpful error", :bundler => "3"
+    pending "should fail with a helpful error", :bundler => "3"
   end
 
   describe "bundle config" do
@@ -292,7 +292,7 @@ RSpec.describe "major deprecations" do
       G
     end
 
-    it "should output a deprecation warning", :bundler => "< 3" do
+    it "should output a deprecation warning", :bundler => "2" do
       expect(deprecations).to include("The --binstubs option will be removed in favor of `bundle binstubs --all`")
     end
 
@@ -356,7 +356,7 @@ RSpec.describe "major deprecations" do
           bundle "install #{flag_name} #{value}"
         end
 
-        it "should print a deprecation warning", :bundler => "< 3" do
+        it "should print a deprecation warning", :bundler => "2" do
           expect(deprecations).to include(
             "The `#{flag_name}` flag is deprecated because it relies on " \
             "being remembered across bundler invocations, which bundler " \
@@ -365,7 +365,7 @@ RSpec.describe "major deprecations" do
           )
         end
 
-        pending "fails with a helpful error", :bundler => "3"
+        pending "should fail with a helpful error", :bundler => "3"
       end
     end
   end
@@ -378,58 +378,18 @@ RSpec.describe "major deprecations" do
       G
     end
 
-    it "shows a deprecation", :bundler => "< 3" do
+    it "shows a deprecation", :bundler => "2" do
       expect(deprecations).to include(
         "Your Gemfile contains multiple primary sources. " \
         "Using `source` more than once without a block is a security risk, and " \
         "may result in installing unexpected gems. To resolve this warning, use " \
-        "a block to indicate which gems should come from the secondary source."
+        "a block to indicate which gems should come from the secondary source. " \
+        "To upgrade this warning to an error, run `bundle config set --local " \
+        "disable_multisource true`."
       )
     end
 
-    pending "fails with a helpful error", :bundler => "3"
-  end
-
-  context "bundle install with a lockfile with a single rubygems section with multiple remotes in frozen mode" do
-    before do
-      build_repo gem_repo3 do
-        build_gem "rack", "0.9.1"
-      end
-
-      gemfile <<-G
-        source "#{file_uri_for(gem_repo1)}"
-        source "#{file_uri_for(gem_repo3)}" do
-          gem 'rack'
-        end
-      G
-
-      lockfile <<~L
-        GEM
-          remote: #{file_uri_for(gem_repo1)}/
-          remote: #{file_uri_for(gem_repo3)}/
-          specs:
-            rack (0.9.1)
-
-        PLATFORMS
-          ruby
-
-        DEPENDENCIES
-          rack!
-
-        BUNDLED WITH
-           #{Bundler::VERSION}
-      L
-
-      bundle "config set --local deployment true"
-    end
-
-    it "shows a deprecation", :bundler => "< 3" do
-      bundle "install"
-
-      expect(deprecations).to include("Your lockfile contains a single rubygems source section with multiple remotes, which is insecure. You should regenerate your lockfile in a non frozen environment.")
-    end
-
-    pending "fails with a helpful error", :bundler => "3"
+    pending "should fail with a helpful error", :bundler => "3"
   end
 
   context "when Bundler.setup is run in a ruby script" do
@@ -462,14 +422,14 @@ RSpec.describe "major deprecations" do
       RUBY
     end
 
-    it "should print a capistrano deprecation warning", :bundler => "< 3" do
+    it "should print a capistrano deprecation warning", :bundler => "2" do
       expect(deprecations).to include("Bundler no longer integrates " \
                              "with Capistrano, but Capistrano provides " \
                              "its own integration with Bundler via the " \
                              "capistrano-bundler gem. Use it instead.")
     end
 
-    pending "fails with a helpful error", :bundler => "3"
+    pending "should fail with a helpful error", :bundler => "3"
   end
 
   describe Bundler::Dsl do
@@ -479,7 +439,7 @@ RSpec.describe "major deprecations" do
     end
 
     context "with github gems" do
-      it "does not warn about removal", :bundler => "< 3" do
+      it "does not warn about removal", :bundler => "2" do
         expect(Bundler.ui).not_to receive(:warn)
         subject.gem("sparks", :github => "indirect/sparks")
         github_uri = "https://github.com/indirect/sparks.git"
@@ -501,7 +461,7 @@ The :github git source is deprecated, and will be removed in the future. Change
     end
 
     context "with bitbucket gems" do
-      it "does not warn about removal", :bundler => "< 3" do
+      it "does not warn about removal", :bundler => "2" do
         expect(Bundler.ui).not_to receive(:warn)
         subject.gem("not-really-a-gem", :bitbucket => "mcorp/flatlab-rails")
       end
@@ -523,7 +483,7 @@ The :bitbucket git source is deprecated, and will be removed in the future. Add
     end
 
     context "with gist gems" do
-      it "does not warn about removal", :bundler => "< 3" do
+      it "does not warn about removal", :bundler => "2" do
         expect(Bundler.ui).not_to receive(:warn)
         subject.gem("not-really-a-gem", :gist => "1234")
       end
@@ -554,7 +514,7 @@ The :gist git source is deprecated, and will be removed in the future. Add this
         bundle :show
       end
 
-      it "prints a deprecation warning recommending `bundle list`", :bundler => "< 3" do
+      it "prints a deprecation warning recommending `bundle list`", :bundler => "2" do
         expect(deprecations).to include("use `bundle list` instead of `bundle show`")
       end
 
@@ -566,7 +526,7 @@ The :gist git source is deprecated, and will be removed in the future. Add this
         bundle "show --outdated"
       end
 
-      it "prints a deprecation warning informing about its removal", :bundler => "< 3" do
+      it "prints a deprecation warning informing about its removal", :bundler => "2" do
         expect(deprecations).to include("the `--outdated` flag to `bundle show` was undocumented and will be removed without replacement")
       end
 
@@ -578,7 +538,7 @@ The :gist git source is deprecated, and will be removed in the future. Add this
         bundle "show --verbose"
       end
 
-      it "prints a deprecation warning informing about its removal", :bundler => "< 3" do
+      it "prints a deprecation warning informing about its removal", :bundler => "2" do
         expect(deprecations).to include("the `--verbose` flag to `bundle show` was undocumented and will be removed without replacement")
       end
 
@@ -590,7 +550,7 @@ The :gist git source is deprecated, and will be removed in the future. Add this
         bundle "show rack"
       end
 
-      it "prints a deprecation warning recommending `bundle info`", :bundler => "< 3" do
+      it "prints a deprecation warning recommending `bundle info`", :bundler => "2" do
         expect(deprecations).to include("use `bundle info rack` instead of `bundle show rack`")
       end
 
@@ -602,7 +562,7 @@ The :gist git source is deprecated, and will be removed in the future. Add this
         bundle "show --paths"
       end
 
-      it "prints a deprecation warning recommending `bundle list`", :bundler => "< 3" do
+      it "prints a deprecation warning recommending `bundle list`", :bundler => "2" do
         expect(deprecations).to include("use `bundle list` instead of `bundle show --paths`")
       end
 
@@ -614,7 +574,7 @@ The :gist git source is deprecated, and will be removed in the future. Add this
         bundle "show rack --paths"
       end
 
-      it "prints deprecation warning recommending `bundle info`", :bundler => "< 3" do
+      it "prints deprecation warning recommending `bundle info`", :bundler => "2" do
         expect(deprecations).to include("use `bundle info rack --path` instead of `bundle show rack --paths`")
       end
 
@@ -627,7 +587,7 @@ The :gist git source is deprecated, and will be removed in the future. Add this
       bundle "console", :raise_on_error => false
     end
 
-    it "prints a deprecation warning", :bundler => "< 3" do
+    it "prints a deprecation warning", :bundler => "2" do
       expect(deprecations).to include \
         "bundle console will be replaced by `bin/console` generated by `bundle gem <name>`"
     end
@@ -643,7 +603,7 @@ The :gist git source is deprecated, and will be removed in the future. Add this
       bundle "viz"
     end
 
-    it "prints a deprecation warning", :bundler => "< 3" do
+    it "prints a deprecation warning", :bundler => "2" do
       expect(deprecations).to include "The `viz` command has been moved to the `bundle-viz` gem, see https://github.com/bundler/bundler-viz"
     end
 
diff --git a/spec/bundler/support/indexes.rb b/spec/bundler/support/indexes.rb
index 1f3c4ddaa6..45b68541f5 100644
--- a/spec/bundler/support/indexes.rb
+++ b/spec/bundler/support/indexes.rb
@@ -30,7 +30,7 @@ module Spec
       args[1] ||= Bundler::GemVersionPromoter.new # gem_version_promoter
       args[2] ||= [] # additional_base_requirements
       args[3] ||= @platforms # platforms
-      Bundler::Resolver.resolve(deps, source_requirements, *args)
+      Bundler::Resolver.resolve(deps, @index, source_requirements, *args)
     end
 
     def should_resolve_as(specs)
diff --git a/test/rubygems/test_gem.rb b/test/rubygems/test_gem.rb
index 8b028d3495..1c6d790b25 100644
--- a/test/rubygems/test_gem.rb
+++ b/test/rubygems/test_gem.rb
@@ -1958,9 +1958,15 @@ class TestGem < Gem::TestCase
       io.write 'gem "a"'
     end
 
+    platform = Bundler::GemHelpers.generic_local_platform
+    if platform == Gem::Platform::RUBY
+      platform = ''
+    else
+      platform = " #{platform}"
+    end
+
     expected = <<-EXPECTED
-Could not find gem 'a' in locally installed gems.
-The source does not contain any versions of 'a'
+Could not find gem 'a#{platform}' in any of the gem sources listed in your Gemfile.
 You may need to `gem install -g` to install missing gems
 
     EXPECTED
diff --git a/test/rubygems/test_gem_config_file.rb b/test/rubygems/test_gem_config_file.rb
index ddc35a9594..7db31013aa 100644
--- a/test/rubygems/test_gem_config_file.rb
+++ b/test/rubygems/test_gem_config_file.rb
@@ -41,6 +41,7 @@ class TestGemConfigFile < Gem::TestCase
     assert_equal true, @cfg.verbose
     assert_equal [@gem_repo], Gem.sources
     assert_equal 365, @cfg.cert_expiration_length_days
+    assert_equal false, @cfg.ipv4_fallback_enabled
 
     File.open @temp_conf, 'w' do |fp|
       fp.puts ":backtrace: true"
@@ -56,6 +57,7 @@ class TestGemConfigFile < Gem::TestCase
       fp.puts ":ssl_verify_mode: 0"
       fp.puts ":ssl_ca_cert: /etc/ssl/certs"
       fp.puts ":cert_expiration_length_days: 28"
+      fp.puts ":ipv4_fallback_enabled: true"
     end
 
     util_config_file
@@ -70,6 +72,14 @@ class TestGemConfigFile < Gem::TestCase
     assert_equal 0, @cfg.ssl_verify_mode
     assert_equal '/etc/ssl/certs', @cfg.ssl_ca_cert
     assert_equal 28, @cfg.cert_expiration_length_days
+    assert_equal true, @cfg.ipv4_fallback_enabled
+  end
+
+  def test_initialize_ipv4_fallback_enabled_env
+    ENV['IPV4_FALLBACK_ENABLED'] = 'true'
+    util_config_file %W[--config-file #{@temp_conf}]
+
+    assert_equal true, @cfg.ipv4_fallback_enabled
   end
 
   def test_initialize_handle_arguments_config_file
diff --git a/test/rubygems/test_gem_remote_fetcher.rb b/test/rubygems/test_gem_remote_fetcher.rb
index 1c88e8d3e8..32600deee2 100644
--- a/test/rubygems/test_gem_remote_fetcher.rb
+++ b/test/rubygems/test_gem_remote_fetcher.rb
@@ -962,6 +962,12 @@ PeIQQkFng2VVot/WAQbv3ePqWq07g1BBcwIBAg==
     end
   end
 
+  def test_tcpsocketext_require
+    with_configured_fetcher(":ipv4_fallback_enabled: true") do |fetcher|
+      refute require('rubygems/core_ext/tcpsocket_init')
+    end
+  end
+
   def with_configured_fetcher(config_str = nil, &block)
     if config_str
       temp_conf = File.join @tempdir, '.gemrc'