WIP

lib/rbi.rb

@@ -16,6 +16,7 @@
 require "rbi/rewriters/nest_non_public_methods"
 require "rbi/rewriters/group_nodes"
 require "rbi/rewriters/remove_known_definitions"
+require "rbi/rewriters/replace_attributes_with_methods"
 require "rbi/rewriters/sort_nodes"
 require "rbi/parser"
 require "rbi/printer"

lib/rbi/model.rb

@@ -42,6 +42,16 @@ def replace(node)
       self.parent_tree = nil
     end
 
+    sig { params(nodes: T::Enumerable[Node]).void }
+    def replace_with_multiple(nodes)
+      tree = parent_tree
+      raise unless tree
+
+      # Does this work?
+      nodes.each { |node| tree << node }
+      detach
+    end
+
     sig { returns(T.nilable(Scope)) }
     def parent_scope
       parent = T.let(parent_tree, T.nilable(Tree))

lib/rbi/rewriters/replace_attributes_with_methods.rb

@@ -0,0 +1,177 @@
+# typed: strict
+# frozen_string_literal: true
+
+module RBI
+  module Rewriters
+    class ReplaceAttributesWithMethods < Visitor
+      extend T::Sig
+
+      sig { override.params(node: T.nilable(Node)).void }
+      def visit(node)
+        return unless node
+
+        case node
+        when Tree
+          node.nodes.dup.each do |child|
+            visit(child)
+            next unless child.is_a?(Attr)
+
+            child.replace_with_multiple(child.convert_to_methods)
+            child.detach
+          end
+        end
+      end
+    end
+  end
+
+  class Attr
+    sig { abstract.returns(T.nilable(String)) }
+    def attribute_type; end
+
+    sig { abstract.returns(T::Array[Method]) }
+    def convert_to_methods; end
+
+    sig { returns(T.nilable(Sig)) }
+    def ensure_max_one_sig!
+      raise "Attributes cannot have more than 1 sig" unless sigs.one?
+
+      sigs.first
+    end
+  end
+
+  class AttrReader
+    sig { override.returns(T.nilable(String)) }
+    def attribute_type = ensure_max_one_sig!&.return_type
+
+    sig { override.returns(T::Array[Method]) }
+    def convert_to_methods
+      ensure_max_one_sig!
+      raise "TODO: Support one attr decl with multiple names" unless names.one?
+
+      name = names.first.to_s
+
+      m = Method.new(
+        name,
+        params: [],
+        visibility: visibility,
+        sigs: sigs,
+        loc: loc,
+        comments: comments,
+      )
+
+      [m]
+    end
+  end
+
+  class AttrWriter
+    sig { override.returns(T.nilable(String)) }
+    def attribute_type = ensure_max_one_sig!&.params&.first&.type
+
+    sig { override.returns(T::Array[Method]) }
+    def convert_to_methods
+      ensure_max_one_sig!
+      raise "TODO: Support one attr decl with multiple names" unless names.one?
+
+      name = names.first.to_s
+
+      method_sigs = if (attribute_type = self.attribute_type)
+        [
+          Sig.new(
+            params: [
+              SigParam.new(
+                name,
+                attribute_type,
+                # loc: ???
+                # comments: ???
+              ),
+            ],
+            return_type: attribute_type,
+          ),
+        ]
+      else
+        []
+      end
+
+      m = Method.new(
+        "#{name}=",
+        params: [
+          ReqParam.new(
+            name,
+            # loc: ???
+            # comments: ???
+          ),
+        ],
+        visibility: visibility,
+        sigs: method_sigs,
+        loc: loc,
+        comments: comments,
+      )
+
+      [m]
+    end
+  end
+
+  class AttrAccessor
+    sig { override.returns(T.nilable(String)) }
+    def attribute_type = ensure_max_one_sig!&.return_type
+
+    sig { override.returns(T::Array[Method]) }
+    def convert_to_methods
+      split_into_reader_writer.flat_map(&:convert_to_methods)
+    end
+
+    sig { returns([AttrReader, AttrWriter]) }
+    def split_into_reader_writer
+      ensure_max_one_sig!
+      raise "TODO: Support one attr decl with multiple names" unless names.one?
+
+      name = names.first.to_s
+
+      reader = AttrReader.new(
+        *T.unsafe(names),
+        visibility: visibility,
+        sigs: attribute_type ? [Sig.new(return_type: attribute_type)] : [],
+        loc: loc,
+        comments: comments,
+      )
+
+      writer_sigs = if (attribute_type = self.attribute_type)
+        [
+          Sig.new(
+            params: [
+              SigParam.new(
+                name,
+                attribute_type,
+                # loc: ???
+                # comments: ???
+              ),
+            ],
+            return_type: attribute_type,
+          ),
+        ]
+      else
+        []
+      end
+
+      writer = AttrWriter.new(
+        *T.unsafe(names),
+        visibility: visibility,
+        sigs: writer_sigs,
+        loc: loc,
+        comments: comments,
+      )
+
+      [reader, writer]
+    end
+  end
+
+  class Tree
+    extend T::Sig
+
+    sig { void }
+    def replace_attributes_with_methods!
+      visitor = Rewriters::ReplaceAttributesWithMethods.new
+      visitor.visit(self)
+    end
+  end
+end

test/rbi/rewriters/replace_attributes_with_methods_test.rb

@@ -0,0 +1,65 @@
+# typed: true
+# frozen_string_literal: true
+
+require "test_helper"
+
+module RBI
+  class ReplaceAttributesWithMethods < Minitest::Test
+    # TODO: Handle `attr_reader :a, :b, :c`
+
+    def test_replaces_attr_reader_with_method
+      rbi = Parser.parse_string(<<~RBI)
+        sig { returns(Integer) }
+        attr_reader :a
+      RBI
+
+      rbi.replace_attributes_with_methods!
+
+      assert_equal(<<~RBI, rbi.string)
+        sig { returns(Integer) }
+        def a; end
+      RBI
+    end
+
+    def test_replaces_attr_writer_with_setter_method
+      # TODO: Should we look for `.void`, `.returns(Integer)`, or either?
+      rbi = Parser.parse_string(<<~RBI)
+        sig { params(a: Integer).void }
+        attr_writer :a
+      RBI
+
+      rbi.replace_attributes_with_methods!
+
+      # TODO: Should we generate `.void` or `.returns(Integer)`?
+      #
+      # I think `.returns(Integer)`, because that's what the method _actually_ returns:
+      #
+      # class C
+      #   attr_writer :foo
+      # end
+      #
+      # C.new.send(:foo=, 123) # => 123
+      assert_equal(<<~RBI, rbi.string)
+        sig { params(a: Integer).returns(Integer) }
+        def a=(a); end
+      RBI
+    end
+
+    def test_replaces_attr_accessor_with_getter_and_setter_methods
+      rbi = Parser.parse_string(<<~RBI)
+        sig { returns(Integer) }
+        attr_accessor :a
+      RBI
+
+      rbi.replace_attributes_with_methods!
+
+      assert_equal(<<~RBI, rbi.string)
+        sig { returns(Integer) }
+        def a; end
+
+        sig { params(a: Integer).returns(Integer) }
+        def a=(a); end
+      RBI
+    end
+  end
+end