Let Gitlab/RailsLogger check only log methods

The use of e.g. `Rails.logger.level` is fine for historical reasons.

rubocop/cop/gitlab/rails_logger.rb

@@ -8,7 +8,7 @@ module RuboCop
       class RailsLogger < ::RuboCop::Cop::Cop
         include CodeReuseHelpers
 
-        # This cop checks for the Rails.logger in the codebase
+        # This cop checks for the Rails.logger log methods in the codebase
         #
         # @example
         #
@@ -17,15 +17,26 @@ module RuboCop
         #
         #   # good
         #   Gitlab::AppLogger.error("Project %{project_path} could not be saved" % { project_path: project.full_path })
+        #
+        #   # OK
+        #   Rails.logger.level
         MSG = 'Use a structured JSON logger instead of `Rails.logger`. ' \
           'https://docs.gitlab.com/ee/development/logging.html'.freeze
 
-        def_node_matcher :rails_logger?, <<~PATTERN
-          (send (const nil? :Rails) :logger ... )
+        # See supported log methods:
+        # https://ruby-doc.org/stdlib-2.6.6/libdoc/logger/rdoc/Logger.html
+        LOG_METHODS = %i[debug error fatal info warn].freeze
+        LOG_METHODS_PATTERN = LOG_METHODS.map(&:inspect).join(' ').freeze
+
+        def_node_matcher :rails_logger_log?, <<~PATTERN
+          (send
+            (send (const nil? :Rails) :logger)
+            {#{LOG_METHODS_PATTERN}} ...
+          )
         PATTERN
 
         def on_send(node)
-          return unless rails_logger?(node)
+          return unless rails_logger_log?(node)
 
           add_offense(node, location: :expression)
         end

spec/rubocop/cop/gitlab/rails_logger_spec.rb

@@ -10,22 +10,12 @@ RSpec.describe RuboCop::Cop::Gitlab::RailsLogger, type: :rubocop do
 
   subject(:cop) { described_class.new }
 
-  it 'flags the use of Rails.logger.error with a constant receiver' do
-    inspect_source("Rails.logger.error('some error')")
+  described_class::LOG_METHODS.each do |method|
+    it "flags the use of Rails.logger.#{method} with a constant receiver" do
+      inspect_source("Rails.logger.#{method}('some error')")
 
-    expect(cop.offenses.size).to eq(1)
-  end
-
-  it 'flags the use of Rails.logger.info with a constant receiver' do
-    inspect_source("Rails.logger.info('some info')")
-
-    expect(cop.offenses.size).to eq(1)
-  end
-
-  it 'flags the use of Rails.logger.warn with a constant receiver' do
-    inspect_source("Rails.logger.warn('some warning')")
-
-    expect(cop.offenses.size).to eq(1)
+      expect(cop.offenses.size).to eq(1)
+    end
   end
 
   it 'does not flag the use of Rails.logger with a constant that is not Rails' do
@@ -39,4 +29,10 @@ RSpec.describe RuboCop::Cop::Gitlab::RailsLogger, type: :rubocop do
 
     expect(cop.offenses.size).to eq(0)
   end
+
+  it 'does not flag the use of Rails.logger.level' do
+    inspect_source("Rails.logger.level")
+
+    expect(cop.offenses.size).to eq(0)
+  end
 end