Add compiler for ActiveRecord delegated types

lib/tapioca/dsl/compilers/active_record_delegated_types.rb

@@ -0,0 +1,163 @@
+# typed: strict
+# frozen_string_literal: true
+
+begin
+  require "active_record"
+rescue LoadError
+  return
+end
+
+require "tapioca/dsl/helpers/active_record_column_type_helper"
+require "tapioca/dsl/helpers/active_record_constants_helper"
+
+module Tapioca
+  module Dsl
+    module Compilers
+      # `Tapioca::Dsl::Compilers::DelegatedTypes` defines RBI files for subclasses of
+      # [`ActiveRecord::Base`](https://api.rubyonrails.org/classes/ActiveRecord/Base.html).
+      # This compiler is only responsible for defining the methods that would be created for delegated_types that
+      # are defined in the Active Record model.
+      #
+      # For example, with the following model class:
+      #
+      # ~~~rb
+      # class Entry < ActiveRecord::Base
+      #   delegated_type :entryable, types: %w[ Message Comment ]
+      # end
+      # ~~~
+      #
+      # this compiler will produce the following methods in the RBI file
+      # `entry.rbi`:
+      #
+      # ~~~rbi
+      # # entry.rbi
+      # # typed: true
+      #
+      # class Entry
+      #   include GeneratedDelegatedTypeMethods
+      #
+      #   module GeneratedDelegatedTypeMethods
+      #     sig { params(args: T.untyped).returns(T.any(Message, Comment)) }
+      #     def build_entryable(*args); end
+      #
+      #     sig { returns(Class) }
+      #     def entryable_class; end
+      #
+      #     sig { returns(ActiveSupport::StringInquirer) }
+      #     def entryable_name; end
+      #
+      #     sig { returns(T::Boolean) }
+      #     def message?; end
+      #
+      #     sig { returns(T.nilable(Message)) }
+      #     def message; end
+      #
+      #     sig { returns(T.nilable(Integer)) }
+      #     def message_id; end
+      #
+      #     sig { returns(T::Boolean) }
+      #     def comment?; end
+      #
+      #     sig { returns(T.nilable(Comment)) }
+      #     def comment; end
+      #
+      #     sig { returns(T.nilable(Integer)) }
+      #     def comment_id; end
+      #   end
+      # end
+      #
+      # ~~~
+      class ActiveRecordDelegatedTypes < Compiler
+        extend T::Sig
+        include Helpers::ActiveRecordConstantsHelper
+
+        ConstantType = type_member { { fixed: T.all(T.class_of(ActiveRecord::Base), Extensions::ActiveRecord) } }
+
+        sig { override.void }
+        def decorate
+          return if constant.__tapioca_delegated_types.nil?
+
+          root.create_path(constant) do |model|
+            model.create_module(DelegatedTypesModuleName) do |mod|
+              constant.__tapioca_delegated_types.each do |role, data|
+                types = data.fetch(:types)
+                options = data.fetch(:options, {})
+                populate_role_accessors(mod, role, types)
+                populate_type_helpers(mod, role, types, options)
+              end
+            end
+
+            model.create_include(DelegatedTypesModuleName)
+          end
+        end
+
+        class << self
+          extend T::Sig
+
+          sig { override.returns(T::Enumerable[Module]) }
+          def gather_constants
+            descendants_of(::ActiveRecord::Base).reject(&:abstract_class?)
+          end
+        end
+
+        private
+
+        sig { params(mod: RBI::Scope, role: Symbol, types: T::Array[String]).void }
+        def populate_role_accessors(mod, role, types)
+          mod.create_method(
+            "#{role}_name",
+            parameters: [],
+            return_type: "ActiveSupport::StringInquirer",
+          )
+
+          mod.create_method(
+            "#{role}_class",
+            parameters: [],
+            return_type: "Class",
+          )
+
+          mod.create_method(
+            "build_#{role}",
+            parameters: [create_rest_param("args", type: "T.untyped")],
+            return_type: "T.any(#{types.join(", ")})",
+          )
+        end
+
+        sig { params(mod: RBI::Scope, role: Symbol, types: T::Array[String], options: T::Hash[Symbol, T.untyped]).void }
+        def populate_type_helpers(mod, role, types, options)
+          types.each do |type|
+            populate_type_helper(mod, role, type, options)
+          end
+        end
+
+        sig { params(mod: RBI::Scope, role: Symbol, type: String, options: T::Hash[Symbol, T.untyped]).void }
+        def populate_type_helper(mod, role, type, options)
+          singular   = type.tableize.tr("/", "_").singularize
+          query      = "#{singular}?"
+          primary_key = options[:primary_key] || "id"
+          role_id = options[:foreign_key] || "#{role}_id"
+
+          getter_type, _ = Helpers::ActiveRecordColumnTypeHelper.new(constant).type_for(role_id.to_s)
+
+          mod.create_method(
+            query,
+            parameters: [],
+            return_type: "T::Boolean",
+          )
+
+          mod.create_method(
+            singular,
+            parameters: [],
+            return_type: "T.nilable(#{type})",
+          )
+
+          mod.create_method(
+            "#{singular}_#{primary_key}",
+            parameters: [],
+            return_type: as_nilable_type(getter_type),
+          )
+        end
+      end
+    end
+  end
+end

lib/tapioca/dsl/extensions/active_record.rb

@@ -0,0 +1,29 @@
+# typed: true
+# frozen_string_literal: true
+
+begin
+  require "active_record"
+rescue LoadError
+  return
+end
+
+module Tapioca
+  module Dsl
+    module Compilers
+      module Extensions
+        module ActiveRecord
+          attr_reader :__tapioca_delegated_types
+
+          def delegated_type(role, types:, **options)
+            @__tapioca_delegated_types ||= {}
+            @__tapioca_delegated_types[role] = { types: types, options: options }
+
+            super
+          end
+
+          ::ActiveRecord::Base.singleton_class.prepend(self)
+        end
+      end
+    end
+  end
+end

lib/tapioca/dsl/helpers/active_record_constants_helper.rb

@@ -13,6 +13,7 @@ module ActiveRecordConstantsHelper
 
         AttributeMethodsModuleName = T.let("GeneratedAttributeMethods", String)
         AssociationMethodsModuleName = T.let("GeneratedAssociationMethods", String)
+        DelegatedTypesModuleName = T.let("GeneratedDelegatedTypeMethods", String)
 
         RelationMethodsModuleName = T.let("GeneratedRelationMethods", String)
         AssociationRelationMethodsModuleName = T.let("GeneratedAssociationRelationMethods", String)

manual/compiler_activerecorddelegatedtypes.md

@@ -0,0 +1,56 @@
+## ActiveRecordDelegatedTypes
+
+`Tapioca::Dsl::Compilers::DelegatedTypes` defines RBI files for subclasses of
+[`ActiveRecord::Base`](https://api.rubyonrails.org/classes/ActiveRecord/Base.html).
+This compiler is only responsible for defining the methods that would be created for delegated_types that
+are defined in the Active Record model.
+
+For example, with the following model class:
+
+~~~rb
+class Entry < ActiveRecord::Base
+  delegated_type :entryable, types: %w[ Message Comment ]
+end
+~~~
+
+this compiler will produce the following methods in the RBI file
+`entry.rbi`:
+
+~~~rbi
+# entry.rbi
+# typed: true
+
+class Entry
+  include GeneratedDelegatedTypeMethods
+
+  module GeneratedDelegatedTypeMethods
+    sig { params(args: T.untyped).returns(T.any(Message, Comment)) }
+    def build_entryable(*args); end
+
+    sig { returns(Class) }
+    def entryable_class; end
+
+    sig { returns(ActiveSupport::StringInquirer) }
+    def entryable_name; end
+
+    sig { returns(T::Boolean) }
+    def message?; end
+
+    sig { returns(T.nilable(Message)) }
+    def message; end
+
+    sig { returns(T.nilable(Integer)) }
+    def message_id; end
+
+    sig { returns(T::Boolean) }
+    def comment?; end
+
+    sig { returns(T.nilable(Comment)) }
+    def comment; end
+
+    sig { returns(T.nilable(Integer)) }
+    def comment_id; end
+  end
+end
+
+~~~

manual/compilers.md

@@ -11,6 +11,7 @@ In the following section you will find all available DSL compilers:
 * [ActiveModelSecurePassword](compiler_activemodelsecurepassword.md)
 * [ActiveRecordAssociations](compiler_activerecordassociations.md)
 * [ActiveRecordColumns](compiler_activerecordcolumns.md)
+* [ActiveRecordDelegatedTypes](compiler_activerecorddelegatedtypes.md)
 * [ActiveRecordEnum](compiler_activerecordenum.md)
 * [ActiveRecordFixtures](compiler_activerecordfixtures.md)
 * [ActiveRecordRelations](compiler_activerecordrelations.md)

spec/tapioca/cli/dsl_spec.rb

@@ -1869,6 +1869,7 @@ class PostCompiler < Tapioca::Dsl::Compiler
               Tapioca::Dsl::Compilers::ActiveModelSecurePassword       enabled
               Tapioca::Dsl::Compilers::ActiveRecordAssociations        enabled
               Tapioca::Dsl::Compilers::ActiveRecordColumns             enabled
+              Tapioca::Dsl::Compilers::ActiveRecordDelegatedTypes      enabled
               Tapioca::Dsl::Compilers::ActiveRecordEnum                enabled
               Tapioca::Dsl::Compilers::ActiveRecordRelations           enabled
               Tapioca::Dsl::Compilers::ActiveRecordScope               enabled
@@ -1897,6 +1898,7 @@ class PostCompiler < Tapioca::Dsl::Compiler
               Tapioca::Dsl::Compilers::ActiveModelSecurePassword       enabled
               Tapioca::Dsl::Compilers::ActiveRecordAssociations        enabled
               Tapioca::Dsl::Compilers::ActiveRecordColumns             enabled
+              Tapioca::Dsl::Compilers::ActiveRecordDelegatedTypes      enabled
               Tapioca::Dsl::Compilers::ActiveRecordEnum                disabled
               Tapioca::Dsl::Compilers::ActiveRecordRelations           enabled
               Tapioca::Dsl::Compilers::ActiveRecordScope               enabled
@@ -1925,6 +1927,7 @@ class PostCompiler < Tapioca::Dsl::Compiler
               Tapioca::Dsl::Compilers::ActiveModelSecurePassword       disabled
               Tapioca::Dsl::Compilers::ActiveRecordAssociations        disabled
               Tapioca::Dsl::Compilers::ActiveRecordColumns             disabled
+              Tapioca::Dsl::Compilers::ActiveRecordDelegatedTypes      disabled
               Tapioca::Dsl::Compilers::ActiveRecordEnum                enabled
               Tapioca::Dsl::Compilers::ActiveRecordRelations           disabled
               Tapioca::Dsl::Compilers::ActiveRecordScope               disabled