[rubygems/rubygems] Raise an error when top level dependency does not resolve under all locked platforms

https://github.com/rubygems/rubygems/commit/25304f3e8d

lib/bundler/resolver.rb

@@ -248,8 +248,22 @@ module Bundler
       results = filter_matching_specs(results, locked_requirement) if locked_requirement
 
       versions = results.group_by(&:version).reduce([]) do |groups, (version, specs)|
-        platform_specs = package.platforms.flat_map {|platform| select_best_platform_match(specs, platform) }
-        next groups if platform_specs.empty?
+        platform_specs = package.platforms.map {|platform| select_best_platform_match(specs, platform) }
+
+        # If package is a top-level dependency,
+        #   candidate is only valid if there are matching versions for all resolution platforms.
+        #
+        # If package is not a top-level deependency,
+        #   then it's not necessary that it has matching versions for all platforms, since it may have been introduced only as
+        #   a dependency for a platform specific variant, so it will only need to have a valid version for that platform.
+        #
+        if package.top_level?
+          next groups if platform_specs.any?(&:empty?)
+        else
+          next groups if platform_specs.all?(&:empty?)
+        end
+
+        platform_specs.flatten!
 
         ruby_specs = select_best_platform_match(specs, Gem::Platform::RUBY)
         groups << Resolver::Candidate.new(version, :specs => ruby_specs) if ruby_specs.any?

lib/bundler/resolver/package.rb

@@ -21,6 +21,7 @@ module Bundler
         @locked_version = locked_specs[name].first&.version
         @unlock = unlock
         @dependency = dependency || Dependency.new(name, @locked_version)
+        @top_level = !dependency.nil?
         @prerelease = @dependency.prerelease? || @locked_version&.prerelease? || prerelease ? :consider_first : :ignore
       end
 
@@ -32,6 +33,10 @@ module Bundler
         false
       end
 
+      def top_level?
+        @top_level
+      end
+
       def meta?
         @name.end_with?("\0")
       end

spec/bundler/install/gems/resolving_spec.rb

@@ -425,6 +425,62 @@ RSpec.describe "bundle install with install-time dependencies" do
         end
       end
 
+      context "when adding a new gem that does not resolve under all locked platforms" do
+        before do
+          simulate_platform "x86_64-linux" do
+            build_repo4 do
+              build_gem "nokogiri", "1.14.0" do |s|
+                s.platform = "x86_64-linux"
+              end
+              build_gem "nokogiri", "1.14.0" do |s|
+                s.platform = "arm-linux"
+              end
+
+              build_gem "sorbet-static", "0.5.10696" do |s|
+                s.platform = "x86_64-linux"
+              end
+            end
+
+            lockfile <<~L
+              GEM
+                remote: #{file_uri_for(gem_repo4)}/
+                specs:
+                  nokogiri (1.14.0-arm-linux)
+                  nokogiri (1.14.0-x86_64-linux)
+
+              PLATFORMS
+                arm-linux
+                x86_64-linux
+
+              DEPENDENCIES
+                nokogiri
+
+              BUNDLED WITH
+                 #{Bundler::VERSION}
+            L
+
+            gemfile <<~G
+              source "#{file_uri_for(gem_repo4)}"
+
+              gem "nokogiri"
+              gem "sorbet-static"
+            G
+
+            bundle "lock", :raise_on_error => false
+          end
+        end
+
+        it "raises a proper error" do
+          nice_error = <<~E.strip
+            Could not find gems matching 'sorbet-static' valid for all resolution platforms (arm-linux, x86_64-linux) in rubygems repository #{file_uri_for(gem_repo4)}/ or installed locally.
+
+            The source contains the following gems matching 'sorbet-static':
+              * sorbet-static-0.5.10696-x86_64-linux
+          E
+          expect(err).to end_with(nice_error)
+        end
+      end
+
       it "gives a meaningful error on ruby version mismatches between dependencies" do
         build_repo4 do
           build_gem "requires-old-ruby" do |s|