[Fix #9580] Add New Cop to Enforce Bundler Gem filename

changelog/fix_enforce_gem_file_name.md

@@ -0,0 +1 @@
+* [#9580](https://github.com/rubocop/rubocop/issues/9580): Add a new cop that enforces which bundler gem file to use. ([@gregfletch][])

config/default.yml

@@ -174,6 +174,20 @@ Bundler/GemComment:
   IgnoredGems: []
   OnlyFor: []
 
+Bundler/GemFilename:
+  Description: 'Enforces the filename for managing gems.'
+  Enabled: true
+  VersionAdded: '<<next>>'
+  EnforcedStyle: 'Gemfile'
+  SupportedStyles:
+    - 'Gemfile'
+    - 'gems.rb'
+  Include:
+    - '**/Gemfile'
+    - '**/gems.rb'
+    - '**/Gemfile.lock'
+    - '**/gems.locked'
+
 Bundler/GemVersion:
   Description: 'Requires or forbids specifying gem versions.'
   Enabled: false

lib/rubocop.rb

@@ -152,6 +152,7 @@
 
 require_relative 'rubocop/cop/bundler/duplicated_gem'
 require_relative 'rubocop/cop/bundler/gem_comment'
+require_relative 'rubocop/cop/bundler/gem_filename'
 require_relative 'rubocop/cop/bundler/gem_version'
 require_relative 'rubocop/cop/bundler/insecure_protocol_source'
 require_relative 'rubocop/cop/bundler/ordered_gems'

lib/rubocop/cop/bundler/gem_filename.rb

@@ -0,0 +1,103 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Bundler
+      # This cop verifies that a project contains Gemfile or gems.rb file and correct
+      # associated lock file based on the configuration.
+      #
+      # @example EnforcedStyle: Gemfile (default)
+      #   # bad
+      #   Project contains gems.rb and gems.locked files
+      #
+      #   # bad
+      #   Project contains Gemfile and gems.locked file
+      #
+      #   # good
+      #   Project contains Gemfile and Gemfile.lock
+      #
+      # @example EnforcedStyle: gems.rb
+      #   # bad
+      #   Project contains Gemfile and Gemfile.lock files
+      #
+      #   # bad
+      #   Project contains gems.rb and Gemfile.lock file
+      #
+      #   # good
+      #   Project contains gems.rb and gems.locked files
+      class GemFilename < Base
+        include ConfigurableEnforcedStyle
+        include RangeHelp
+
+        MSG_GEMFILE_REQUIRED = '`gems.rb` file was found but `Gemfile` is required '\
+                               '(file path: %<file_path>s).'
+        MSG_GEMS_RB_REQUIRED = '`Gemfile` was found but `gems.rb` file is required '\
+                               '(file path: %<file_path>s).'
+        MSG_GEMFILE_MISMATCHED = 'Expected a `Gemfile.lock` with `Gemfile` but found '\
+                                 '`gems.locked` file (file path: %<file_path>s).'
+        MSG_GEMS_RB_MISMATCHED = 'Expected a `gems.locked` file with `gems.rb` but found '\
+                                 '`Gemfile.lock` (file path: %<file_path>s).'
+        GEMFILE_FILES = %w[Gemfile Gemfile.lock].freeze
+        GEMS_RB_FILES = %w[gems.rb gems.locked].freeze
+
+        def on_new_investigation
+          file_path = processed_source.file_path
+          basename = File.basename(file_path)
+          return if expected_gemfile?(basename)
+
+          register_offense(file_path, basename)
+        end
+
+        private
+
+        def register_offense(file_path, basename)
+          register_gemfile_offense(file_path, basename) if gemfile_offense?(basename)
+          register_gems_rb_offense(file_path, basename) if gems_rb_offense?(basename)
+        end
+
+        def register_gemfile_offense(file_path, basename)
+          message = case basename
+                    when 'gems.rb'
+                      MSG_GEMFILE_REQUIRED
+                    when 'gems.locked'
+                      MSG_GEMFILE_MISMATCHED
+                    end
+
+          add_global_offense(format(message, file_path: file_path))
+        end
+
+        def register_gems_rb_offense(file_path, basename)
+          message = case basename
+                    when 'Gemfile'
+                      MSG_GEMS_RB_REQUIRED
+                    when 'Gemfile.lock'
+                      MSG_GEMS_RB_MISMATCHED
+                    end
+
+          add_global_offense(format(message, file_path: file_path))
+        end
+
+        def gemfile_offense?(basename)
+          gemfile_required? && GEMS_RB_FILES.include?(basename)
+        end
+
+        def gems_rb_offense?(basename)
+          gems_rb_required? && GEMFILE_FILES.include?(basename)
+        end
+
+        def expected_gemfile?(basename)
+          (gemfile_required? && GEMFILE_FILES.include?(basename)) ||
+            (gems_rb_required? && GEMS_RB_FILES.include?(basename))
+        end
+
+        def gemfile_required?
+          style == :Gemfile
+        end
+
+        def gems_rb_required?
+          style == :'gems.rb'
+        end
+      end
+    end
+  end
+end

spec/rubocop/cop/bundler/gem_filename_spec.rb

@@ -0,0 +1,139 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Bundler::GemFilename, :config do
+  shared_examples_for 'invalid gem file' do |message|
+    it 'registers an offense' do
+      offenses = _investigate(cop, processed_source)
+
+      expect(offenses.size).to eq(1)
+      expect(offenses.first.message).to eq(message)
+    end
+  end
+
+  shared_examples_for 'valid gem file' do
+    it 'does not register an offense' do
+      offenses = _investigate(cop, processed_source)
+
+      expect(offenses.size).to eq(0)
+    end
+  end
+
+  context 'with default configuration (EnforcedStyle => `Gemfile`)' do
+    let(:source) { 'print 1' }
+    let(:processed_source) { parse_source(source) }
+
+    before { allow(processed_source.buffer).to receive(:name).and_return(filename) }
+
+    context 'with gems.rb file path' do
+      let(:filename) { 'gems.rb' }
+
+      include_examples 'invalid gem file',
+                       '`gems.rb` file was found but `Gemfile` is required '\
+                       '(file path: gems.rb).'
+    end
+
+    context 'with non-root gems.rb file path' do
+      let(:filename) { 'spec/gems.rb' }
+
+      include_examples 'invalid gem file',
+                       '`gems.rb` file was found but `Gemfile` is required '\
+                       '(file path: spec/gems.rb).'
+    end
+
+    context 'with gems.locked file path' do
+      let(:filename) { 'gems.locked' }
+
+      include_examples 'invalid gem file',
+                       'Expected a `Gemfile.lock` with `Gemfile` but found `gems.locked` file '\
+                       '(file path: gems.locked).'
+    end
+
+    context 'with non-root gems.locked file path' do
+      let(:filename) { 'spec/gems.locked' }
+
+      include_examples 'invalid gem file',
+                       'Expected a `Gemfile.lock` with `Gemfile` but found `gems.locked` file '\
+                       '(file path: spec/gems.locked).'
+    end
+
+    context 'with Gemfile file path' do
+      let(:filename) { 'Gemfile' }
+
+      include_examples 'valid gem file'
+    end
+
+    context 'with non-root Gemfile file path' do
+      let(:filename) { 'spec/Gemfile' }
+
+      include_examples 'valid gem file'
+    end
+
+    context 'with Gemfile.lock file path' do
+      let(:filename) { 'Gemfile.lock' }
+
+      include_examples 'valid gem file'
+    end
+
+    context 'with non-root Gemfile.lock file path' do
+      let(:filename) { 'spec/Gemfile.lock' }
+
+      include_examples 'valid gem file'
+    end
+  end
+
+  context 'with EnforcedStyle set to `gems.rb`' do
+    let(:source) { 'print 1' }
+    let(:processed_source) { parse_source(source) }
+    let(:cop_config) { { 'EnforcedStyle' => 'gems.rb' } }
+
+    before { allow(processed_source.buffer).to receive(:name).and_return(filename) }
+
+    context 'with Gemfile file path' do
+      let(:filename) { 'Gemfile' }
+
+      include_examples 'invalid gem file', '`Gemfile` was found but `gems.rb` file is required '\
+                                           '(file path: Gemfile).'
+    end
+
+    context 'with non-root Gemfile file path' do
+      let(:filename) { 'spec/Gemfile' }
+
+      include_examples 'invalid gem file', '`Gemfile` was found but `gems.rb` file is required '\
+                                           '(file path: spec/Gemfile).'
+    end
+
+    context 'with Gemfile.lock file path' do
+      let(:filename) { 'Gemfile.lock' }
+
+      include_examples 'invalid gem file',
+                       'Expected a `gems.locked` file with `gems.rb` but found `Gemfile.lock` '\
+                       '(file path: Gemfile.lock).'
+    end
+
+    context 'with non-root Gemfile.lock file path' do
+      let(:filename) { 'spec/Gemfile.lock' }
+
+      include_examples 'invalid gem file',
+                       'Expected a `gems.locked` file with `gems.rb` but found `Gemfile.lock` '\
+                       '(file path: spec/Gemfile.lock).'
+    end
+
+    context 'with gems.rb file path' do
+      let(:filename) { 'gems.rb' }
+
+      include_examples 'valid gem file'
+    end
+
+    context 'with non-root gems.rb file path' do
+      let(:filename) { 'spec/gems.rb' }
+
+      include_examples 'valid gem file'
+    end
+
+    context 'with non-root gems.locked file path' do
+      let(:filename) { 'spec/gems.locked' }
+
+      include_examples 'valid gem file'
+    end
+  end
+end