Don't warn about default gems missing from Gemfile.lock

lib/rbs/collection/config/lockfile_generator.rb

@@ -179,7 +179,7 @@ def generate
               end
             end
           else
-            unless NONGEM_STDLIBS.include?(name)
+            unless NONGEM_STDLIBS.include?(name) || default_gem?(name)
               RBS.logger.warn "Cannot find `#{name}` gem. Using incorrect Bundler context? (#{definition.lockfile})"
             end
           end
@@ -250,6 +250,11 @@ def generate
           end
         end
 
+        # Default gems are always available without being listed in Gemfile.lock.
+        private def default_gem?(name)
+          Gem::Specification.default_stubs("#{name}-*.gemspec").any? { |stub| stub.name == name }
+        end
+
         private def find_source(name:)
           sources = config.sources
 

sig/collection/config/lockfile_generator.rbs

@@ -55,6 +55,10 @@ module RBS
         #
         def assign_stdlib: (name: String, ?from_gem: String) -> void
 
+        # Returns `true` if a default gem with the name is installed.
+        #
+        def default_gem?: (String name) -> bool
+
         # Find a source of a gem from ones registered in `config.sources`
         #
         # Returns `nil` if no source contains the definition of the gem.

sig/shims/rubygems.rbs

@@ -6,9 +6,15 @@ module Gem
 
     def self.find_by_name: (String name, *String requirements) -> instance
 
+    def self.default_stubs: (?String pattern) -> Array[StubSpecification]
+
     def dependencies: () -> Array[Dependency]
   end
 
+  class StubSpecification
+    def name: () -> String
+  end
+
   class Dependency
     def name: () -> String
   end

test/rbs/cli_test.rb

@@ -1648,7 +1648,12 @@ def test_collection_install__pathname_set
         bundle_install('ast', 'logger', 'tsort')
         _stdout, stderr = run_rbs_collection("install", bundler: true)
 
-        assert_include stderr, 'Cannot find `set` gem.'
+        # `set` is a default gem until Ruby 3.5, where it became a core class.
+        if Gem::Specification.default_stubs("set-*.gemspec").any? { _1.name == "set" }
+          refute_match(/Cannot find `set` gem/, stderr)
+        else
+          assert_include stderr, 'Cannot find `set` gem.'
+        end
 
         lockfile = RBS::Collection::Config::Lockfile.from_lockfile(
           lockfile_path: dir + "rbs_collection.lock.yaml",

test/rbs/collection/config_test.rb

@@ -697,6 +697,50 @@ def test_generate_lockfile__gems_not_included_in_gemfile
     end
   end
 
+  def test_generate_lockfile__default_gems_not_included_in_gemfile
+    omit unless Gem::Specification.default_stubs("un-*.gemspec").any? { _1.name == "un" }
+
+    mktmpdir do |tmpdir|
+      config_path = tmpdir / 'rbs_collection.yaml'
+      config_path.write <<~YAML
+        sources: []
+        path: '.gem_rbs_collection'
+        gems:
+          - name: un
+      YAML
+      gemfile_path = tmpdir / 'Gemfile'
+      gemfile_path.write <<~GEMFILE
+        source 'https://rubygems.org'
+      GEMFILE
+      gemfile_lock_path = tmpdir / 'Gemfile.lock'
+      gemfile_lock_path.write <<~GEMFILE_LOCK
+        GEM
+          remote: https://rubygems.org/
+          specs:
+
+        PLATFORMS
+          x86_64-linux
+
+        DEPENDENCIES
+
+        BUNDLED WITH
+           2.2.0
+      GEMFILE_LOCK
+
+      definition = Bundler::Definition.build(gemfile_path, gemfile_lock_path, false)
+
+      log = StringIO.new
+      RBS.logger_output = log
+      begin
+        RBS::Collection::Config.generate_lockfile(config_path: config_path, definition: definition)
+      ensure
+        RBS.logger_output = nil
+      end
+
+      refute_match(/Cannot find `un` gem/, log.string)
+    end
+  end
+
   def test_generate_lockfile__dependency_source
     mktmpdir do |tmpdir|
       config_path = tmpdir / 'rbs_collection.yaml'