[rubygems/rubygems] Always resolve against the local platform

If RUBY is the only platform in the lockfile, we were skipping adding
the local platform to the list of resolution platforms. This generally
works anyways, because we had some code to still add it if the RUBY
platform is not valid for the set of locked gems.

However, sometimes it can happen that "RUBY" is valid for the current
set of locked gems, but when adding a new dependency, it becomes
invalid. For example, when adding sorbet to a Gemfile, that will
introduce `sorbet-static` as an indirect dependency which does not have
a generic "RUBY" variant. This will cause resolution to take a long time
continuously backtracking trying to find solutions that don't introduce
`sorbet-static` as a dependency and will eventually fail.

Instead, we can always add the local platform to the set of resolution
platforms before resolving, and remove it as necessary after resolution
so that we lock the correct set of platforms.

rubygems/rubygems@6ed1fe6050

Author: deivid-rodriguez

lib/bundler/definition.rb

@@ -624,6 +624,11 @@ def start_resolution
       result = SpecSet.new(resolver.start)
 
       @resolved_bundler_version = result.find {|spec| spec.name == "bundler" }&.version
+
+      if @current_ruby_locked_platform && @current_ruby_locked_platform != local_platform
+        @platforms.delete(result.incomplete_for_platform?(dependencies, @current_ruby_locked_platform) ? @current_ruby_locked_platform : local_platform)
+      end
+
       @platforms = result.add_extra_platforms!(platforms) if should_add_extra_platforms?
 
       result.complete_platforms!(platforms)
@@ -661,7 +666,7 @@ def current_platform_locked?
     end
 
     def add_current_platform
-      return if current_ruby_platform_locked?
+      @current_ruby_locked_platform = most_specific_locked_platform if current_ruby_platform_locked?
 
       add_platform(local_platform)
     end
@@ -1049,7 +1054,6 @@ def remove_invalid_platforms!(dependencies)
                 !@originally_locked_specs.incomplete_for_platform?(dependencies, platform)
 
         remove_platform(platform)
-        add_current_platform if platform == Gem::Platform::RUBY
       end
     end
 

spec/bundler/install/gemfile/specific_platform_spec.rb

@@ -1066,6 +1066,60 @@
     end
   end
 
+  it "automatically fixes the lockfile when only RUBY platform locked, and adding a dependency with subdependencies not valid for RUBY" do
+    simulate_platform "x86_64-linux" do
+      build_repo4 do
+        build_gem("sorbet", "0.5.10160") do |s|
+          s.add_runtime_dependency "sorbet-static", "= 0.5.10160"
+        end
+
+        build_gem("sorbet-static", "0.5.10160") do |s|
+          s.platform = "x86_64-linux"
+        end
+      end
+
+      gemfile <<~G
+        source "#{file_uri_for(gem_repo4)}"
+
+        gem "sorbet"
+      G
+
+      lockfile <<~L
+        GEM
+          remote: #{file_uri_for(gem_repo4)}/
+          specs:
+
+        PLATFORMS
+          ruby
+
+        DEPENDENCIES
+
+        BUNDLED WITH
+           #{Bundler::VERSION}
+      L
+
+      bundle "lock"
+
+      expect(lockfile).to eq <<~L
+        GEM
+          remote: #{file_uri_for(gem_repo4)}/
+          specs:
+            sorbet (0.5.10160)
+              sorbet-static (= 0.5.10160)
+            sorbet-static (0.5.10160-x86_64-linux)
+
+        PLATFORMS
+          x86_64-linux
+
+        DEPENDENCIES
+          sorbet
+
+        BUNDLED WITH
+           #{Bundler::VERSION}
+      L
+    end
+  end
+
   it "locks specific platforms automatically" do
     simulate_platform "x86_64-linux" do
       build_repo4 do