Implement RuboCop DSL compiler

This generates RBI signatures for use of Rubocop's Node Pattern macros (`def_node_matcher` & `def_node_search`).
Shopify · Oct 28, 2022 · 57670ce · 57670ce
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diff --git a/lib/tapioca/dsl/compilers/rubocop.rb b/lib/tapioca/dsl/compilers/rubocop.rb
@@ -0,0 +1,66 @@
+# typed: strict
+# frozen_string_literal: true
+
+begin
+  require "rubocop"
+rescue LoadError
+  return
+end
+
+module Tapioca
+  module Dsl
+    module Compilers
+      # `Tapioca::Dsl::Compilers::RuboCop` generates types for RuboCop cops.
+      # RuboCop uses macros to define methods leveraging "AST node patterns".
+      # For example, in this cop
+      #
+      #   class MyCop < Base
+      #     def_node_matcher :matches_some_pattern?, "..."
+      #
+      #     def on_send(node)
+      #       return unless matches_some_pattern?(node)
+      #       # ...
+      #     end
+      #   end
+      #
+      # the use of `def_node_matcher` will generate the method
+      # `matches_some_pattern?`, for which this compiler will generate a `sig`.
+      #
+      # More complex uses are also supported, including:
+      #
+      # - Usage of `def_node_search`
+      # - Parameter specification
+      # - Default parameter specification, including generating sigs for
+      #   `without_defaults_*` methods
+      class RuboCop < Compiler
+        ConstantType = type_member { { fixed: T.all(T.class_of(::RuboCop::Cop::Base), Extensions::RuboCop) } }
+
+        class << self
+          extend T::Sig
+          sig { override.returns(T::Enumerable[Class]) }
+          def gather_constants
+            descendants_of(::RuboCop::Cop::Base).select { |constant| name_of(constant) }
+          end
+        end
+
+        sig { override.void }
+        def decorate
+          return if node_methods.empty?
+
+          root.create_path(constant) do |cop_klass|
+            node_methods.each do |name|
+              create_method_from_def(cop_klass, constant.instance_method(name))
+            end
+          end
+        end
+
+        private
+
+        sig { returns(T::Array[Extensions::RuboCop::MethodName]) }
+        def node_methods
+          constant.__tapioca_node_methods
+        end
+      end
+    end
+  end
+end
diff --git a/lib/tapioca/dsl/extensions/rubocop.rb b/lib/tapioca/dsl/extensions/rubocop.rb
@@ -0,0 +1,46 @@
+# typed: strict
+# frozen_string_literal: true
+
+begin
+  require "rubocop"
+rescue LoadError
+  return
+end
+
+module Tapioca
+  module Dsl
+    module Compilers
+      module Extensions
+        module RuboCop
+          extend T::Sig
+
+          MethodName = T.type_alias { T.any(String, Symbol) }
+
+          sig { params(name: MethodName, _args: T.untyped, defaults: T.untyped).returns(MethodName) }
+          def def_node_matcher(name, *_args, **defaults)
+            __tapioca_node_methods << name
+            __tapioca_node_methods << :"without_defaults_#{name}" unless defaults.empty?
+
+            super
+          end
+
+          sig { params(name: MethodName, _args: T.untyped, defaults: T.untyped).returns(MethodName) }
+          def def_node_search(name, *_args, **defaults)
+            __tapioca_node_methods << name
+            __tapioca_node_methods << :"without_defaults_#{name}" unless defaults.empty?
+
+            super
+          end
+
+          sig { returns(T::Array[MethodName]) }
+          def __tapioca_node_methods
+            @__tapioca_node_methods = T.let(@__tapioca_node_methods, T.nilable(T::Array[MethodName]))
+            @__tapioca_node_methods ||= []
+          end
+
+          ::RuboCop::Cop::Base.singleton_class.prepend(self)
+        end
+      end
+    end
+  end
+end
diff --git a/manual/compiler_rubocop.md b/manual/compiler_rubocop.md
@@ -0,0 +1,24 @@
+## RuboCop
+
+`Tapioca::Dsl::Compilers::RuboCop` generates types for RuboCop cops.
+RuboCop uses macros to define methods leveraging "AST node patterns".
+For example, in this cop
+
+  class MyCop < Base
+    def_node_matcher :matches_some_pattern?, "..."
+
+    def on_send(node)
+      return unless matches_some_pattern?(node)
+      # ...
+    end
+  end
+
+the use of `def_node_matcher` will generate the method
+`matches_some_pattern?`, for which this compiler will generate a `sig`.
+
+More complex uses are also supported, including:
+
+- Usage of `def_node_search`
+- Parameter specification
+- Default parameter specification, including generating sigs for
+  `without_defaults_*` methods
diff --git a/manual/compilers.md b/manual/compilers.md
@@ -28,6 +28,7 @@ In the following section you will find all available DSL compilers:
 * [MixedInClassAttributes](compiler_mixedinclassattributes.md)
 * [Protobuf](compiler_protobuf.md)
 * [RailsGenerators](compiler_railsgenerators.md)
+* [RuboCop](compiler_rubocop.md)
 * [SidekiqWorker](compiler_sidekiqworker.md)
 * [SmartProperties](compiler_smartproperties.md)
 * [StateMachines](compiler_statemachines.md)

diff --git a/spec/tapioca/dsl/compilers/rubocop_spec.rb b/spec/tapioca/dsl/compilers/rubocop_spec.rb
@@ -0,0 +1,166 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "spec_helper"
+require "rubocop"
+require "rubocop-sorbet"
+
+module Tapioca
+  module Dsl
+    module Compilers
+      class RuboCopSpec < ::DslSpec
+        # Collect constants from gems, before defining any in tests.
+        EXISTING_CONSTANTS = T.let(
+          Runtime::Reflection
+            .descendants_of(::RuboCop::Cop::Base)
+            .filter_map { |constant| Runtime::Reflection.name_of(constant) },
+          T::Array[String],
+        )
+
+        class << self
+          extend T::Sig
+
+          sig { override.returns(String) }
+          def target_class_file
+            # Against convention, RuboCop uses "rubocop" in its file names, so we do too.
+            super.gsub("rubo_cop", "rubocop")
+          end
+        end
+
+        describe "Tapioca::Dsl::Compilers::RuboCop" do
+          sig { void }
+          def before_setup
+            require "tapioca/dsl/extensions/rubocop"
+            super
+          end
+
+          describe "initialize" do
+            it "gathered constants exclude irrelevant classes" do
+              add_ruby_file("content.rb", <<~RUBY)
+                class Unrelated
+                end
+              RUBY
+              assert_empty(relevant_gathered_constants)
+            end
+
+            it "gathers constants inheriting RuboCop::Cop::Base in gems" do
+              # Sample of miscellaneous constants that should be found from Rubocop and plugins
+              missing_constants = [
+                "RuboCop::Cop::Bundler::GemVersion",
+                "RuboCop::Cop::Cop",
+                "RuboCop::Cop::Gemspec::DependencyVersion",
+                "RuboCop::Cop::Lint::Void",
+                "RuboCop::Cop::Metrics::ClassLength",
+                "RuboCop::Cop::Migration::DepartmentName",
+                "RuboCop::Cop::Naming::MethodName",
+                "RuboCop::Cop::Security::CompoundHash",
+                "RuboCop::Cop::Sorbet::ValidSigil",
+                "RuboCop::Cop::Style::YodaCondition",
+              ] - gathered_constants
+
+              assert_empty(missing_constants, "expected constants to be gathered")
+            end
+
+            it "gathers constants inheriting from RuboCop::Cop::Base in the host app" do
+              add_ruby_file("content.rb", <<~RUBY)
+                class MyCop < ::RuboCop::Cop::Base
+                end
+
+                class MyLegacyCop < ::RuboCop::Cop::Cop
+                end
+
+                module ::RuboCop
+                  module Cop
+                    module MyApp
+                      class MyNamespacedCop < Base
+                      end
+                    end
+                  end
+                end
+              RUBY
+
+              assert_equal(
+                ["MyCop", "MyLegacyCop", "RuboCop::Cop::MyApp::MyNamespacedCop"],
+                relevant_gathered_constants,
+              )
+            end
+          end
+
+          describe "decorate" do
+            it "generates empty RBI when no DSL used" do
+              add_ruby_file("content.rb", <<~RUBY)
+                class MyCop < ::RuboCop::Cop::Base
+                  def on_send(node);end
+                end
+              RUBY
+
+              expected = <<~RBI
+                # typed: strong
+              RBI
+
+              assert_equal(expected, rbi_for(:MyCop))
+            end
+
+            it "generates correct RBI file" do
+              add_ruby_file("content.rb", <<~RUBY)
+                class MyCop < ::RuboCop::Cop::Base
+                  def_node_matcher :some_matcher, "(...)"
+                  def_node_matcher :some_matcher_with_params, "(%1 %two ...)"
+                  def_node_matcher :some_matcher_with_params_and_defaults, "(%1 %two ...)", two: :default
+                  def_node_matcher :some_predicate_matcher?, "(...)"
+                  def_node_search :some_search, "(...)"
+                  def_node_search :some_search_with_params, "(%1 %two ...)"
+                  def_node_search :some_search_with_params_and_defaults, "(%1 %two ...)", two: :default
+
+                  def on_send(node);end
+                end
+              RUBY
+
+              expected = <<~RBI
+                # typed: strong
+
+                class MyCop
+                  sig { params(param0: T.untyped).returns(T.untyped) }
+                  def some_matcher(param0 = T.unsafe(nil)); end
+
+                  sig { params(param0: T.untyped, param1: T.untyped, two: T.untyped).returns(T.untyped) }
+                  def some_matcher_with_params(param0 = T.unsafe(nil), param1, two:); end
+
+                  sig { params(args: T.untyped, values: T.untyped).returns(T.untyped) }
+                  def some_matcher_with_params_and_defaults(*args, **values); end
+
+                  sig { params(param0: T.untyped).returns(T.untyped) }
+                  def some_predicate_matcher?(param0 = T.unsafe(nil)); end
+
+                  sig { params(param0: T.untyped).returns(T.untyped) }
+                  def some_search(param0); end
+
+                  sig { params(param0: T.untyped, param1: T.untyped, two: T.untyped).returns(T.untyped) }
+                  def some_search_with_params(param0, param1, two:); end
+
+                  sig { params(args: T.untyped, values: T.untyped).returns(T.untyped) }
+                  def some_search_with_params_and_defaults(*args, **values); end
+
+                  sig { params(param0: T.untyped, param1: T.untyped, two: T.untyped).returns(T.untyped) }
+                  def without_defaults_some_matcher_with_params_and_defaults(param0 = T.unsafe(nil), param1, two:); end
+
+                  sig { params(param0: T.untyped, param1: T.untyped, two: T.untyped).returns(T.untyped) }
+                  def without_defaults_some_search_with_params_and_defaults(param0, param1, two:); end
+                end
+              RBI
+
+              assert_equal(expected, rbi_for(:MyCop))
+            end
+          end
+
+          private
+
+          sig { returns(T::Array[String]) }
+          def relevant_gathered_constants
+            gathered_constants - EXISTING_CONSTANTS
+          end
+        end
+      end
+    end
+  end
+end