[rubygems/rubygems] Don't discard candidates matching ruby metadata

Do dependency filtering and materialization in one step. Before,
dependency filtering would not consider ruby metadata so it would
discard variants that end up not being materializable in the end.

https://github.com/rubygems/rubygems/commit/0c0d40d417

Co-authored-by: Ian Ker-Seymer <ian.kerseymer@shopify.com>

lib/bundler/gem_helpers.rb

@@ -44,6 +44,12 @@ module Bundler
 
     def select_best_platform_match(specs, platform)
       matching = specs.select {|spec| spec.match_platform(platform) }
+
+      sort_best_platform_match(matching, platform)
+    end
+    module_function :select_best_platform_match
+
+    def sort_best_platform_match(matching, platform)
       exact = matching.select {|spec| spec.platform == platform }
       return exact if exact.any?
 
@@ -52,7 +58,7 @@ module Bundler
 
       sorted_matching.take_while {|spec| same_specificity(platform, spec, exemplary_spec) && same_deps(spec, exemplary_spec) }
     end
-    module_function :select_best_platform_match
+    module_function :sort_best_platform_match
 
     class PlatformMatch
       def self.specificity_score(spec_platform, user_platform)

lib/bundler/lazy_specification.rb

@@ -88,6 +88,8 @@ module Bundler
         source.specs.search(self)
       end
 
+      return self if candidates.empty?
+
       __materialize__(candidates)
     end
 
@@ -105,8 +107,8 @@ module Bundler
           spec.is_a?(StubSpecification) ||
             (spec.required_ruby_version.satisfied_by?(Gem.ruby_version) &&
               spec.required_rubygems_version.satisfied_by?(Gem.rubygems_version))
-        end || candidates.last
-        search.dependencies = dependencies if search && (search.is_a?(RemoteSpecification) || search.is_a?(EndpointSpecification))
+        end
+        search.dependencies = dependencies if search && search.full_name == full_name && (search.is_a?(RemoteSpecification) || search.is_a?(EndpointSpecification))
         search
       end
     end

lib/bundler/spec_set.rb

@@ -66,10 +66,6 @@ module Bundler
     def materialize(deps)
       materialized = self.for(deps, true).uniq
 
-      materialized.map! do |s|
-        next s unless s.is_a?(LazySpecification)
-        s.materialize_for_installation || s
-      end
       SpecSet.new(materialized)
     end
 
@@ -180,7 +176,8 @@ module Bundler
     def specs_for_dependency(dep, platform)
       specs_for_name = lookup[dep.name]
       if platform.nil?
-        GemHelpers.select_best_platform_match(specs_for_name.select {|s| Gem::Platform.match_spec?(s) }, Bundler.local_platform)
+        matching_specs = specs_for_name.map {|s| s.materialize_for_installation if Gem::Platform.match_spec?(s) }.compact
+        GemHelpers.sort_best_platform_match(matching_specs, Bundler.local_platform)
       else
         GemHelpers.select_best_platform_match(specs_for_name, dep.force_ruby_platform ? Gem::Platform::RUBY : platform)
       end

spec/bundler/install/gemfile/specific_platform_spec.rb

@@ -374,6 +374,41 @@ RSpec.describe "bundle install with specific platforms" do
     ERROR
   end
 
+  it "can fallback to a source gem when platform gems are incompatible with current ruby version" do
+    setup_multiplatform_gem_with_source_gem
+
+    source = file_uri_for(gem_repo2)
+
+    gemfile <<~G
+      source "#{source}"
+
+      gem "my-precompiled-gem"
+    G
+
+    # simulate lockfile which includes both a precompiled gem with:
+    # - Gem the current platform (with imcompatible ruby version)
+    # - A source gem with compatible ruby version
+    lockfile <<-L
+      GEM
+        remote: #{source}/
+        specs:
+          my-precompiled-gem (3.0.0)
+          my-precompiled-gem (3.0.0-#{Bundler.local_platform})
+
+      PLATFORMS
+        ruby
+        #{Bundler.local_platform}
+
+      DEPENDENCIES
+        my-precompiled-gem
+
+      BUNDLED WITH
+         #{Bundler::VERSION}
+    L
+
+    bundle :install
+  end
+
   private
 
   def setup_multiplatform_gem
@@ -404,4 +439,16 @@ RSpec.describe "bundle install with specific platforms" do
       build_gem("CFPropertyList")
     end
   end
+
+  def setup_multiplatform_gem_with_source_gem
+    build_repo2 do
+      build_gem("my-precompiled-gem", "3.0.0")
+      build_gem("my-precompiled-gem", "3.0.0") do |s|
+        s.platform = Bundler.local_platform
+
+        # purposely unresolvable
+        s.required_ruby_version = ">= 1000.0.0"
+      end
+    end
+  end
 end

spec/bundler/install/gems/resolving_spec.rb

@@ -241,7 +241,7 @@ RSpec.describe "bundle install with install-time dependencies" do
         expect(the_bundle).to include_gems("rack 1.2")
       end
 
-      it "gives a meaningful error if there's a lockfile using the newer incompatible version" do
+      it "automatically updates lockfile to use the older version" do
         build_repo2 do
           build_gem "parallel_tests", "3.7.0" do |s|
             s.required_ruby_version = ">= #{current_ruby_minor}"
@@ -273,9 +273,23 @@ RSpec.describe "bundle install with install-time dependencies" do
              #{Bundler::VERSION}
         L
 
-        bundle "install --verbose", :artifice => "compact_index", :env => { "BUNDLER_SPEC_GEM_REPO" => gem_repo2.to_s }, :raise_on_error => false
-        expect(err).to include("parallel_tests-3.8.0 requires ruby version >= #{next_ruby_minor}")
-        expect(err).not_to include("That means the author of parallel_tests (3.8.0) has removed it.")
+        bundle "install --verbose", :artifice => "compact_index", :env => { "BUNDLER_SPEC_GEM_REPO" => gem_repo2.to_s }
+
+        expect(lockfile).to eq <<~L
+          GEM
+            remote: http://localgemserver.test/
+            specs:
+              parallel_tests (3.7.0)
+
+          PLATFORMS
+            #{lockfile_platforms}
+
+          DEPENDENCIES
+            parallel_tests
+
+          BUNDLED WITH
+             #{Bundler::VERSION}
+        L
       end
 
       it "gives a meaningful error on ruby version mismatches between dependencies" do