Support Prism as a Ruby parser

Follow up rubocop/rubocop-ast#277

Internally, the Parser gem API is used directly to parse db/schema.rb.
This has been replaced with `RuboCop::AST::ProcessedSource` from RuboCop AST 1.31,
which is compatible with the Prism parser API of the Parser gem API.

This change resolves error (e.g., `uninitialized constant Parser::Ruby33`)
related to db/schema.rb parsing when Prism is specified as the parser engine,
enabling paring with Prism.

.github/workflows/test.yml

@@ -53,6 +53,22 @@ jobs:
       - name: internal_investigation
         run: bundle exec rake internal_investigation
 
+  prism:
+    runs-on: ubuntu-latest
+    name: Prism
+    steps:
+      - uses: actions/checkout@v4
+      - name: set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          # Specify the minimum Ruby version 2.7 required for Prism to run.
+          ruby-version: 2.7
+          bundler-cache: true
+      - name: spec
+        env:
+          PARSER_ENGINE: parser_prism
+        run: bundle exec rake prism_spec
+
   documentation_checks:
     runs-on: ubuntu-latest
     name: Check documentation syntax

Gemfile

@@ -7,6 +7,7 @@ git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 gemspec
 
 gem 'bump', require: false
+gem 'prism'
 gem 'rake'
 gem 'rspec'
 gem 'rubocop', github: 'rubocop/rubocop'

Rakefile

@@ -27,6 +27,11 @@ task :spec do
   end
 end
 
+desc 'Run RSpec code examples with Prism'
+task :prism_spec do
+  sh('PARSER_ENGINE=parser_prism bundle exec rake spec')
+end
+
 desc 'Run RSpec with code coverage'
 task :coverage do
   ENV['COVERAGE'] = 'true'
@@ -36,7 +41,7 @@ end
 desc 'Run RuboCop over itself'
 RuboCop::RakeTask.new(:internal_investigation)
 
-task default: %i[documentation_syntax_check spec internal_investigation]
+task default: %i[documentation_syntax_check spec prism_spec internal_investigation]
 
 desc 'Generate a new cop template'
 task :new_cop, [:cop] do |_task, args|

changelog/new_support_prism.md

@@ -0,0 +1 @@
+* [#1245](https://github.com/rubocop/rubocop-rails/pull/1245): Support Prism as a Ruby parser. ([@koic][])

lib/rubocop/cop/mixin/active_record_helper.rb

@@ -39,7 +39,12 @@ def external_dependency_checksum
       end
 
       def schema
-        RuboCop::Rails::SchemaLoader.load(target_ruby_version)
+        # For compatibility with RuboCop 1.16.0 or lower.
+        if respond_to?(:parser_engine)
+          RuboCop::Rails::SchemaLoader.load(target_ruby_version, parser_engine)
+        else
+          RuboCop::Rails::SchemaLoader.load(target_ruby_version, :parser_whitequark)
+        end
       end
 
       def table_name(class_node)

lib/rubocop/rails/schema_loader.rb

@@ -12,10 +12,10 @@ module SchemaLoader
       # So a cop that uses the loader should handle `nil` properly.
       #
       # @return [Schema, nil]
-      def load(target_ruby_version)
+      def load(target_ruby_version, parser_engine)
         return @load if defined?(@load)
 
-        @load = load!(target_ruby_version)
+        @load = load!(target_ruby_version, parser_engine)
       end
 
       def reset!
@@ -38,23 +38,16 @@ def db_schema_path
 
       private
 
-      def load!(target_ruby_version)
+      def load!(target_ruby_version, parser_engine)
         path = db_schema_path
         return unless path
 
-        ast = parse(path, target_ruby_version)
+        ast = parse(path, target_ruby_version, parser_engine)
         Schema.new(ast) if ast
       end
 
-      def parse(path, target_ruby_version)
-        klass_name = :"Ruby#{target_ruby_version.to_s.sub('.', '')}"
-        klass = ::Parser.const_get(klass_name)
-        parser = klass.new(RuboCop::AST::Builder.new)
-
-        buffer = Parser::Source::Buffer.new(path, 1)
-        buffer.source = path.read
-
-        parser.parse(buffer)
+      def parse(path, target_ruby_version, parser_engine)
+        RuboCop::AST::ProcessedSource.new(File.read(path), target_ruby_version, path, parser_engine: parser_engine).ast
       end
     end
   end

rubocop-rails.gemspec

@@ -36,5 +36,5 @@ Gem::Specification.new do |s|
   # introduced in rack 1.1
   s.add_runtime_dependency 'rack', '>= 1.1'
   s.add_runtime_dependency 'rubocop', '>= 1.33.0', '< 2.0'
-  s.add_runtime_dependency 'rubocop-ast', '>= 1.30.0', '< 2.0'
+  s.add_runtime_dependency 'rubocop-ast', '>= 1.31.1', '< 2.0'
 end

spec/rubocop/cop/rails/index_by_spec.rb

@@ -175,7 +175,7 @@
     end
   end
 
-  context 'when using Ruby 2.5 or older', :ruby25 do
+  context 'when using Ruby 2.5 or older', :ruby25, unsupported_on: :prism do
     it 'does not register an offense for `to_h { ... }`' do
       expect_no_offenses(<<~RUBY)
         x.to_h { |el| [el.to_sym, el] }

spec/rubocop/cop/rails/index_with_spec.rb

@@ -148,7 +148,7 @@
       end
     end
 
-    context 'when using Ruby 2.5 or older', :ruby25 do
+    context 'when using Ruby 2.5 or older', :ruby25, unsupported_on: :prism do
       it 'does not register an offense for `to_h { ... }`' do
         expect_no_offenses(<<~RUBY)
           x.to_h { |el| [el, el.to_sym] }

spec/rubocop/cop/rails/root_pathname_methods_spec.rb

@@ -46,7 +46,7 @@
     end
   end
 
-  context 'when using `Dir.glob` on Ruby 2.4 or lower', :ruby24 do
+  context 'when using `Dir.glob` on Ruby 2.4 or lower', :ruby24, unsupported_on: :prism do
     it 'does not registers an offense' do
       expect_no_offenses(<<~RUBY)
         Dir.glob(Rails.root.join('**/*.rb'))

spec/rubocop/cop/rails/safe_navigation_spec.rb

@@ -28,7 +28,7 @@
 
     it_behaves_like 'accepts', 'non try! method calls', 'join'
 
-    context 'target_ruby_version < 2.3', :ruby22 do
+    context 'target_ruby_version < 2.3', :ruby22, unsupported_on: :prism do
       it_behaves_like 'accepts', 'try! with a single parameter', 'try!(:join)'
       it_behaves_like 'accepts', 'try! with a multiple parameters', 'try!(:join, ",")'
       it_behaves_like 'accepts', 'try! with a block', 'try!(:map) { |e| e.some_method }'
@@ -93,7 +93,7 @@
   context 'convert try and try!' do
     let(:cop_config) { { 'ConvertTry' => true } }
 
-    context 'target_ruby_version < 2.3', :ruby22 do
+    context 'target_ruby_version < 2.3', :ruby22, unsupported_on: :prism do
       it_behaves_like 'accepts', 'try! with a single parameter', 'try!(:join)'
       it_behaves_like 'accepts', 'try! with a multiple parameters', 'try!(:join, ",")'
       it_behaves_like 'accepts', 'try! with a block', 'try!(:map) { |e| e.some_method }'

spec/rubocop/cop/rails/strip_heredoc_spec.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 RSpec.describe RuboCop::Cop::Rails::StripHeredoc, :config do
-  context 'Ruby <= 2.2', :ruby22 do
+  context 'Ruby <= 2.2', :ruby22, unsupported_on: :prism do
     it 'does not register an offense when using `strip_heredoc`' do
       expect_no_offenses(<<~RUBY)
         <<-EOS.strip_heredoc

spec/rubocop/rails/schema_loader_spec.rb

@@ -2,8 +2,11 @@
 
 RSpec.describe RuboCop::Rails::SchemaLoader do
   describe '.load' do
-    require 'parser/ruby27'
-    let(:target_ruby_version) { 2.7 }
+    let(:target_ruby_version) do
+      # The minimum version Prism can parse is 3.3.
+      ENV['PARSER_ENGINE'] == 'parser_prism' ? 3.3 : RuboCop::TargetRuby::DEFAULT_VERSION
+    end
+    let(:parser_engine) { ENV.fetch('PARSER_ENGINE', :parser_whitequark).to_sym }
 
     around do |example|
       described_class.reset!
@@ -13,13 +16,13 @@
 
     context 'without schema.rb' do
       it do
-        expect(described_class.load(target_ruby_version).nil?).to be(true)
+        expect(described_class.load(target_ruby_version, parser_engine).nil?).to be(true)
       end
     end
 
     context 'with schema.rb' do
       subject(:loaded_schema) do
-        described_class.load(target_ruby_version)
+        described_class.load(target_ruby_version, parser_engine)
       end
 
       let(:rails_root) { Pathname(Dir.mktmpdir) }

spec/spec_helper.rb

@@ -19,6 +19,10 @@
 
   config.shared_context_metadata_behavior = :apply_to_host_groups
   config.filter_run_when_matching :focus
+
+  # Prism supports Ruby 3.3+ parsing.
+  config.filter_run_excluding unsupported_on: :prism if ENV['PARSER_ENGINE'] == 'parser_prism'
+
   config.example_status_persistence_file_path = 'spec/examples.txt'
   config.disable_monkey_patching!
   config.warnings = true