1 files changed, 149 insertions, 0 deletions
diff --git a/lib/rubygems/vendor/molinillo/lib/molinillo/errors.rb b/lib/rubygems/vendor/molinillo/lib/molinillo/errors.rb
new file mode 100644
index 0000000000..07ea5fdf37
--- /dev/null
+++ b/lib/rubygems/vendor/molinillo/lib/molinillo/errors.rb
@@ -0,0 +1,149 @@
+# frozen_string_literal: true
+
+module Gem::Molinillo
+  # An error that occurred during the resolution process
+  class ResolverError < StandardError; end
+
+  # An error caused by searching for a dependency that is completely unknown,
+  # i.e. has no versions available whatsoever.
+  class NoSuchDependencyError < ResolverError
+    # @return [Object] the dependency that could not be found
+    attr_accessor :dependency
+
+    # @return [Array<Object>] the specifications that depended upon {#dependency}
+    attr_accessor :required_by
+
+    # Initializes a new error with the given missing dependency.
+    # @param [Object] dependency @see {#dependency}
+    # @param [Array<Object>] required_by @see {#required_by}
+    def initialize(dependency, required_by = [])
+      @dependency = dependency
+      @required_by = required_by.uniq
+      super()
+    end
+
+    # The error message for the missing dependency, including the specifications
+    # that had this dependency.
+    def message
+      sources = required_by.map { |r| "`#{r}`" }.join(' and ')
+      message = "Unable to find a specification for `#{dependency}`"
+      message += " depended upon by #{sources}" unless sources.empty?
+      message
+    end
+  end
+
+  # An error caused by attempting to fulfil a dependency that was circular
+  #
+  # @note This exception will be thrown if and only if a {Vertex} is added to a
+  #   {DependencyGraph} that has a {DependencyGraph::Vertex#path_to?} an
+  #   existing {DependencyGraph::Vertex}
+  class CircularDependencyError < ResolverError
+    # [Set<Object>] the dependencies responsible for causing the error
+    attr_reader :dependencies
+
+    # Initializes a new error with the given circular vertices.
+    # @param [Array<DependencyGraph::Vertex>] vertices the vertices in the dependency
+    #   that caused the error
+    def initialize(vertices)
+      super "There is a circular dependency between #{vertices.map(&:name).join(' and ')}"
+      @dependencies = vertices.map { |vertex| vertex.payload.possibilities.last }.to_set
+    end
+  end
+
+  # An error caused by conflicts in version
+  class VersionConflict < ResolverError
+    # @return [{String => Resolution::Conflict}] the conflicts that caused
+    #   resolution to fail
+    attr_reader :conflicts
+
+    # @return [SpecificationProvider] the specification provider used during
+    #   resolution
+    attr_reader :specification_provider
+
+    # Initializes a new error with the given version conflicts.
+    # @param [{String => Resolution::Conflict}] conflicts see {#conflicts}
+    # @param [SpecificationProvider] specification_provider see {#specification_provider}
+    def initialize(conflicts, specification_provider)
+      pairs = []
+      conflicts.values.flat_map(&:requirements).each do |conflicting|
+        conflicting.each do |source, conflict_requirements|
+          conflict_requirements.each do |c|
+            pairs << [c, source]
+          end
+        end
+      end
+
+      super "Unable to satisfy the following requirements:\n\n" \
+        "#{pairs.map { |r, d| "- `#{r}` required by `#{d}`" }.join("\n")}"
+
+      @conflicts = conflicts
+      @specification_provider = specification_provider
+    end
+
+    require_relative 'delegates/specification_provider'
+    include Delegates::SpecificationProvider
+
+    # @return [String] An error message that includes requirement trees,
+    #   which is much more detailed & customizable than the default message
+    # @param [Hash] opts the options to create a message with.
+    # @option opts [String] :solver_name The user-facing name of the solver
+    # @option opts [String] :possibility_type The generic name of a possibility
+    # @option opts [Proc] :reduce_trees A proc that reduced the list of requirement trees
+    # @option opts [Proc] :printable_requirement A proc that pretty-prints requirements
+    # @option opts [Proc] :additional_message_for_conflict A proc that appends additional
+    #   messages for each conflict
+    # @option opts [Proc] :version_for_spec A proc that returns the version number for a
+    #   possibility
+    def message_with_trees(opts = {})
+      solver_name = opts.delete(:solver_name) { self.class.name.split('::').first }
+      possibility_type = opts.delete(:possibility_type) { 'possibility named' }
+      reduce_trees = opts.delete(:reduce_trees) { proc { |trees| trees.uniq.sort_by(&:to_s) } }
+      printable_requirement = opts.delete(:printable_requirement) { proc { |req| req.to_s } }
+      additional_message_for_conflict = opts.delete(:additional_message_for_conflict) { proc {} }
+      version_for_spec = opts.delete(:version_for_spec) { proc(&:to_s) }
+      incompatible_version_message_for_conflict = opts.delete(:incompatible_version_message_for_conflict) do
+        proc do |name, _conflict|
+          %(#{solver_name} could not find compatible versions for #{possibility_type} "#{name}":)
+        end
+      end
+
+      full_message_for_conflict = opts.delete(:full_message_for_conflict) do
+        proc do |name, conflict|
+          o = "\n".dup << incompatible_version_message_for_conflict.call(name, conflict) << "\n"
+          if conflict.locked_requirement
+            o << %(  In snapshot (#{name_for_locking_dependency_source}):\n)
+            o << %(    #{printable_requirement.call(conflict.locked_requirement)}\n)
+            o << %(\n)
+          end
+          o << %(  In #{name_for_explicit_dependency_source}:\n)
+          trees = reduce_trees.call(conflict.requirement_trees)
+
+          o << trees.map do |tree|
+            t = ''.dup
+            depth = 2
+            tree.each do |req|
+              t << '  ' * depth << printable_requirement.call(req)
+              unless tree.last == req
+                if spec = conflict.activated_by_name[name_for(req)]
+                  t << %( was resolved to #{version_for_spec.call(spec)}, which)
+                end
+                t << %( depends on)
+              end
+              t << %(\n)
+              depth += 1
+            end
+            t
+          end.join("\n")
+
+          additional_message_for_conflict.call(o, name, conflict)
+
+          o
+        end
+      end
+
+      conflicts.sort.reduce(''.dup) do |o, (name, conflict)|
+        o << full_message_for_conflict.call(name, conflict)
+      end.strip
+    end
+  end
+end