Suppress spurious warning for non-gem stdlib libraries

When running `rbs collection install` with an existing lockfile that
includes non-gem standard libraries (like socket, pathname), the
lockfile generator would emit a misleading warning:

  Cannot find `socket` gem. Using incorrect Bundler context?

This happens because these libraries are part of Ruby's standard
library but are not distributed as gems, so they never appear in
Bundler's gem specifications. With an existing lockfile, the code
path bypasses stdlib detection and falls through to the gem_hash
lookup, which fails and triggers the warning.

Add NONGEM_STDLIBS constant listing all non-gem standard libraries
that have type definitions in stdlib/, and skip the warning for them.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: soutaro

lib/rbs/collection/config/lockfile_generator.rb

@@ -21,6 +21,17 @@ class LockfileGenerator
           "pstore" => nil,
         }
 
+        NONGEM_STDLIBS = Set[
+          "cgi-escape",
+          "coverage",
+          "monitor",
+          "objspace",
+          "pathname",
+          "pty",
+          "ripper",
+          "socket",
+        ]
+
         class GemfileLockMismatchError < StandardError
           def initialize(expected:, actual:)
             @expected = expected
@@ -168,7 +179,9 @@ def generate
               end
             end
           else
-            RBS.logger.warn "Cannot find `#{name}` gem. Using incorrect Bundler context? (#{definition.lockfile})"
+            unless NONGEM_STDLIBS.include?(name)
+              RBS.logger.warn "Cannot find `#{name}` gem. Using incorrect Bundler context? (#{definition.lockfile})"
+            end
           end
         end
 

sig/collection/config/lockfile_generator.rbs

@@ -6,6 +6,8 @@ module RBS
         #
         ALUMNI_STDLIBS: Hash[String, String?]
 
+        NONGEM_STDLIBS: Set[String]
+
         class GemfileLockMismatchError < StandardError
           @expected: Pathname
 

test/rbs/cli_test.rb

@@ -1491,6 +1491,54 @@ def test_collection_install__pathname_set
     end
   end
 
+  def test_collection_install__nongem_stdlib_no_warning
+    Dir.mktmpdir do |dir|
+      Dir.chdir(dir) do
+        dir = Pathname(dir)
+        dir.join(RBS::Collection::Config::PATH).write(<<~YAML)
+          sources:
+            - name: ruby/gem_rbs_collection
+              remote: https://github.com/ruby/gem_rbs_collection.git
+              revision: b4d3b346d9657543099a35a1fd20347e75b8c523
+              repo_dir: gems
+
+          path: #{dir.join('gem_rbs_collection')}
+
+          gems:
+          - name: socket
+          - name: pathname
+        YAML
+
+        bundle_install('ast', 'logger', 'tsort')
+
+        # First install creates the lockfile with socket as stdlib
+        _stdout, stderr = run_rbs_collection("install", bundler: true)
+
+        lockfile = RBS::Collection::Config::Lockfile.from_lockfile(
+          lockfile_path: dir + "rbs_collection.lock.yaml",
+          data: YAML.safe_load((dir + "rbs_collection.lock.yaml").read)
+        )
+
+        assert_instance_of RBS::Collection::Sources::Stdlib, lockfile.gems["socket"][:source]
+        assert_instance_of RBS::Collection::Sources::Stdlib, lockfile.gems["pathname"][:source]
+
+        # Second install with existing lockfile should not warn about nongem stdlibs
+        _stdout, stderr = run_rbs_collection("install", bundler: true)
+
+        refute_match(/Cannot find `socket` gem/, stderr)
+        refute_match(/Cannot find `pathname` gem/, stderr)
+
+        lockfile = RBS::Collection::Config::Lockfile.from_lockfile(
+          lockfile_path: dir + "rbs_collection.lock.yaml",
+          data: YAML.safe_load((dir + "rbs_collection.lock.yaml").read)
+        )
+
+        assert_instance_of RBS::Collection::Sources::Stdlib, lockfile.gems["socket"][:source]
+        assert_instance_of RBS::Collection::Sources::Stdlib, lockfile.gems["pathname"][:source]
+      end
+    end
+  end
+
   def test_collection_install__set_pathname__manifest
     Dir.mktmpdir do |dir|
       Dir.chdir(dir) do