Make the config loader Bundler-aware

Before this change, when inheriting a configuration from a gem, rubocop:

1. would fail to find it, if the gem specified in the Gemfile has a `path` or `git` option (because rubygems is unaware of those gems)
2. would always load the config of the latest installed version of a gem, regardless of the version specified in the Gemfile

This commit changes that, so if executed in the context of Bundler (`defined?(Bundler)`) it will first try to get the gem path via Bundler, and fallback to the previous `Gem::Specification` path when not found.

This solves the two mentioned issues while maintaining the possibility to run rubocop in a globally installed context, i.e. without Bundler.

CHANGELOG.md

@@ -26,6 +26,7 @@
 * [#7886](https://github.com/rubocop-hq/rubocop/issues/7886): Fix a bug in `AllowComments` logic in `Lint/SuppressedException`. ([@jonas054][])
 * [#7991](https://github.com/rubocop-hq/rubocop/issues/7991): Fix an error for `Layout/EmptyLinesAroundAttributeAccessor` when attribute method is method chained. ([@koic][])
 * [#7993](https://github.com/rubocop-hq/rubocop/issues/7993): Fix a false positive for `Migration/DepartmentName` when a disable comment contains an unexpected character for department name. ([@koic][])
+* [#7983](https://github.com/rubocop-hq/rubocop/pull/7983): Make the config loader Bundler-aware. ([@CvX][])
 
 ### Changes
 
@@ -4538,3 +4539,4 @@
 [@jeffcarbs]: https://github.com/jeffcarbs
 [@laurmurclar]: https://github.com/laurmurclar
 [@jethrodaniel]: https://github.com/jethrodaniel
+[@CvX]: https://github.com/CvX

lib/rubocop/config_loader_resolver.rb

@@ -208,8 +208,14 @@ def transform(config)
     end
 
     def gem_config_path(gem_name, relative_config_path)
-      spec = Gem::Specification.find_by_name(gem_name)
-      File.join(spec.gem_dir, relative_config_path)
+      if defined?(Bundler)
+        gem = Bundler.load.specs[gem_name].first
+        gem_path = gem.full_gem_path if gem
+      end
+
+      gem_path ||= Gem::Specification.find_by_name(gem_name).gem_dir
+
+      File.join(gem_path, relative_config_path)
     rescue Gem::LoadError => e
       raise Gem::LoadError,
             "Unable to find gem #{gem_name}; is the gem installed? #{e}"

spec/rubocop/config_loader_spec.rb

@@ -823,31 +823,65 @@ class Loop < Cop
         YAML
       end
 
-      it 'returns values from the gem config with local overrides' do
-        gem_class = Struct.new(:gem_dir)
-        %w[gemone gemtwo].each do |gem_name|
-          mock_spec = gem_class.new(File.join(gem_root, gem_name))
-          allow(Gem::Specification).to receive(:find_by_name)
-            .with(gem_name).and_return(mock_spec)
+      context 'and the gem is globally installed' do
+        before do
+          gem_class = Struct.new(:gem_dir)
+          %w[gemone gemtwo].each do |gem_name|
+            mock_spec = gem_class.new(File.join(gem_root, gem_name))
+            allow(Gem::Specification).to receive(:find_by_name)
+              .with(gem_name).and_return(mock_spec)
+          end
+          allow(Gem).to receive(:path).and_return([gem_root])
         end
-        allow(Gem).to receive(:path).and_return([gem_root])
 
-        expected = { 'Enabled' => true,        # overridden in .rubocop.yml
-                     'CountComments' => true,  # overridden in local.yml
-                     'Max' => 200 }            # inherited from somegem
-        expect do
-          expect(configuration_from_file['Metrics/MethodLength']
-                   .to_set.superset?(expected.to_set)).to be(true)
-        end.to output('').to_stderr
+        it 'returns values from the gem config with local overrides' do
+          expected = { 'Enabled' => true, # overridden in .rubocop.yml
+                       'CountComments' => true,  # overridden in local.yml
+                       'Max' => 200 }            # inherited from somegem
+          expect do
+            expect(configuration_from_file['Metrics/MethodLength']
+                    .to_set.superset?(expected.to_set)).to be(true)
+          end.to output('').to_stderr
+
+          expected = { 'Enabled' => true, # gemtwo/config/default.yml
+                       'Max' => 72,              # gemtwo/config/strict.yml
+                       'AllowHeredoc' => false,  # gemtwo/config/strict.yml
+                       'AllowURI' => false }     # overridden in .rubocop.yml
+          expect(
+            configuration_from_file['Layout/LineLength']
+              .to_set.superset?(expected.to_set)
+          ).to be(true)
+        end
+      end
+
+      context 'and the gem is bundled' do
+        before do
+          specs = {
+            'gemone' => [OpenStruct.new(full_gem_path: File.join(gem_root, 'gemone'))],
+            'gemtwo' => [OpenStruct.new(full_gem_path: File.join(gem_root, 'gemtwo'))]
+          }
 
-        expected = { 'Enabled' => true,        # gemtwo/config/default.yml
-                     'Max' => 72,              # gemtwo/config/strict.yml
-                     'AllowHeredoc' => false,  # gemtwo/config/strict.yml
-                     'AllowURI' => false }     # overridden in .rubocop.yml
-        expect(
-          configuration_from_file['Layout/LineLength']
-            .to_set.superset?(expected.to_set)
-        ).to be(true)
+          allow(Bundler).to receive(:load).and_return(OpenStruct.new(specs: specs))
+        end
+
+        it 'returns values from the gem config with local overrides' do
+          expected = { 'Enabled' => true, # overridden in .rubocop.yml
+                       'CountComments' => true,  # overridden in local.yml
+                       'Max' => 200 }            # inherited from somegem
+          expect do
+            expect(configuration_from_file['Metrics/MethodLength']
+                    .to_set.superset?(expected.to_set)).to be(true)
+          end.to output('').to_stderr
+
+          expected = { 'Enabled' => true, # gemtwo/config/default.yml
+                       'Max' => 72,              # gemtwo/config/strict.yml
+                       'AllowHeredoc' => false,  # gemtwo/config/strict.yml
+                       'AllowURI' => false }     # overridden in .rubocop.yml
+          expect(
+            configuration_from_file['Layout/LineLength']
+              .to_set.superset?(expected.to_set)
+          ).to be(true)
+        end
       end
     end