1 files changed, 39 insertions, 20 deletions
diff --git a/lib/rubygems/resolver/api_specification.rb b/lib/rubygems/resolver/api_specification.rb
index 1e22dd0b6f..ccfd6fe084 100644
--- a/lib/rubygems/resolver/api_specification.rb
+++ b/lib/rubygems/resolver/api_specification.rb
@@ -1,17 +1,28 @@
 # frozen_string_literal: true
+
 ##
-# Represents a specification retrieved via the rubygems.org API.
+# Represents a specification retrieved via the Compact Index API.
 #
 # This is used to avoid loading the full Specification object when all we need
 # is the name, version, and dependencies.
 
 class Gem::Resolver::APISpecification < Gem::Resolver::Specification
+  ##
+  # We assume that all instances of this class are immutable;
+  # so avoid duplicated generation for performance.
+  @@cache = {}
+  def self.new(set, api_data)
+    cache_key = [set, api_data]
+    cache = @@cache[cache_key]
+    return cache if cache
+    @@cache[cache_key] = super
+  end
 
   ##
-  # Creates an APISpecification for the given +set+ from the rubygems.org
+  # Creates an APISpecification for the given +set+ from the Compact Index API
   # +api_data+.
   #
-  # See http://guides.rubygems.org/rubygems-org-api/#misc_methods for the
+  # See https://guides.rubygems.org/rubygems-org-compact-index-api for the
   # format of the +api_data+.
 
   def initialize(set, api_data)
@@ -19,20 +30,26 @@ class Gem::Resolver::APISpecification < Gem::Resolver::Specification
 
     @set = set
     @name = api_data[:name]
-    @version = Gem::Version.new api_data[:number]
-    @platform = Gem::Platform.new api_data[:platform]
+    @version = Gem::Version.new(api_data[:number]).freeze
+    @platform = Gem::Platform.new(api_data[:platform]).freeze
+    @original_platform = api_data[:platform].freeze
     @dependencies = api_data[:dependencies].map do |name, ver|
-      Gem::Dependency.new name, ver.split(/\s*,\s*/)
-    end
+      Gem::Dependency.new(name, ver.split(/\s*,\s*/)).freeze
+    end.freeze
+    @required_ruby_version = Gem::Requirement.new(api_data.dig(:requirements, :ruby)).freeze
+    @required_rubygems_version = Gem::Requirement.new(api_data.dig(:requirements, :rubygems)).freeze
   end
 
-  def == other # :nodoc:
-    self.class === other and
-      @set          == other.set and
-      @name         == other.name and
-      @version      == other.version and
-      @platform     == other.platform and
-      @dependencies == other.dependencies
+  def ==(other) # :nodoc:
+    self.class === other &&
+      @set          == other.set &&
+      @name         == other.name &&
+      @version      == other.version &&
+      @platform     == other.platform
+  end
+
+  def hash
+    @set.hash ^ @name.hash ^ @version.hash ^ @platform.hash
   end
 
   def fetch_development_dependencies # :nodoc:
@@ -42,11 +59,11 @@ class Gem::Resolver::APISpecification < Gem::Resolver::Specification
   end
 
   def installable_platform? # :nodoc:
-    Gem::Platform.match @platform
+    Gem::Platform.match_gem? @platform, @name
   end
 
-  def pretty_print q # :nodoc:
-    q.group 2, '[APISpecification', ']' do
+  def pretty_print(q) # :nodoc:
+    q.group 2, "[APISpecification", "]" do
       q.breakable
       q.text "name: #{name}"
 
@@ -57,7 +74,7 @@ class Gem::Resolver::APISpecification < Gem::Resolver::Specification
       q.text "platform: #{platform}"
 
       q.breakable
-      q.text 'dependencies:'
+      q.text "dependencies:"
       q.breakable
       q.pp @dependencies
 
@@ -73,7 +90,11 @@ class Gem::Resolver::APISpecification < Gem::Resolver::Specification
     @spec ||=
       begin
         tuple = Gem::NameTuple.new @name, @version, @platform
+        source.fetch_spec tuple
+      rescue Gem::RemoteFetcher::FetchError
+        raise if @original_platform == @platform
 
+        tuple = Gem::NameTuple.new @name, @version, @original_platform
         source.fetch_spec tuple
       end
   end
@@ -81,6 +102,4 @@ class Gem::Resolver::APISpecification < Gem::Resolver::Specification
   def source # :nodoc:
     @set.source
   end
-
 end
-