Add rewriter to transform attributes into methods

lib/rbi.rb

@@ -5,7 +5,9 @@
 require "stringio"
 
 module RBI
-  class Error < StandardError; end
+  class Error < StandardError
+    extend T::Sig
+  end
 end
 
 require "rbi/loc"
@@ -21,6 +23,7 @@ class Error < StandardError; end
 require "rbi/rewriters/nest_non_public_methods"
 require "rbi/rewriters/group_nodes"
 require "rbi/rewriters/remove_known_definitions"
+require "rbi/rewriters/attr_to_methods"
 require "rbi/rewriters/sort_nodes"
 require "rbi/parser"
 require "rbi/printer"

lib/rbi/rewriters/attr_to_methods.rb

@@ -0,0 +1,169 @@
+# typed: strict
+# frozen_string_literal: true
+
+module RBI
+  class UnexpectedMultipleSigsError < Error
+    sig { returns(Node) }
+    attr_reader :node
+
+    sig { params(node: Node).void }
+    def initialize(node)
+      super(<<~MSG)
+        This declaration cannot have more than one sig.
+
+        #{node.string.chomp}
+      MSG
+
+      @node = node
+    end
+  end
+
+  module Rewriters
+    class AttrToMethods < Visitor
+      extend T::Sig
+
+      sig { override.params(node: T.nilable(Node)).void }
+      def visit(node)
+        case node
+        when Tree
+          visit_all(node.nodes.dup)
+
+        when Attr
+          replace(node, with: node.convert_to_methods)
+        end
+      end
+
+      private
+
+      sig { params(node: Node, with: T::Array[Node]).void }
+      def replace(node, with:)
+        tree = node.parent_tree
+        raise ReplaceNodeError, "Can't replace #{self} without a parent tree" unless tree
+
+        node.detach
+        with.each { |node| tree << node }
+      end
+    end
+  end
+
+  class Tree
+    extend T::Sig
+
+    sig { void }
+    def replace_attributes_with_methods!
+      visitor = Rewriters::AttrToMethods.new
+      visitor.visit(self)
+    end
+  end
+
+  class Attr
+    sig { abstract.returns(T::Array[Method]) }
+    def convert_to_methods; end
+
+    private
+
+    sig(:final) { returns([T.nilable(Sig), T.nilable(String)]) }
+    def parse_sig
+      raise UnexpectedMultipleSigsError, self if 1 < sigs.count
+
+      sig = sigs.first
+      return [nil, nil] unless sig
+
+      attribute_type = case self
+      when AttrReader, AttrAccessor then sig.return_type
+      when AttrWriter then sig.params.first&.type
+      end
+
+      [sig, attribute_type]
+    end
+
+    sig do
+      params(
+        name: String,
+        sig: T.nilable(Sig),
+        visibility: Visibility,
+        loc: T.nilable(Loc),
+        comments: T::Array[Comment],
+      ).returns(Method)
+    end
+    def create_getter_method(name, sig, visibility, loc, comments)
+      Method.new(
+        name,
+        params: [],
+        visibility: visibility,
+        sigs: sig ? [sig] : [],
+        loc: loc,
+        comments: comments,
+      )
+    end
+
+    sig do
+      params(
+        name: String,
+        sig: T.nilable(Sig),
+        attribute_type: T.nilable(String),
+        visibility: Visibility,
+        loc: T.nilable(Loc),
+        comments: T::Array[Comment],
+      ).returns(Method)
+    end
+    def create_setter_method(name, sig, attribute_type, visibility, loc, comments) # rubocop:disable Metrics/ParameterLists
+      sig = if sig # Modify the original sig to correct the name, and remove the return type
+        params = attribute_type ? [SigParam.new(name, attribute_type)] : []
+
+        Sig.new(
+          params: params,
+          return_type: "void",
+          is_abstract: sig.is_abstract,
+          is_override: sig.is_override,
+          is_overridable: sig.is_overridable,
+          is_final: sig.is_final,
+          type_params: sig.type_params,
+          checked: sig.checked,
+          loc: sig.loc,
+        )
+      end
+
+      Method.new(
+        "#{name}=",
+        params: [ReqParam.new(name)],
+        visibility: visibility,
+        sigs: sig ? [sig] : [],
+        loc: loc,
+        comments: comments,
+      )
+    end
+  end
+
+  class AttrAccessor
+    sig { override.returns(T::Array[Method]) }
+    def convert_to_methods
+      sig, attribute_type = parse_sig
+
+      names.flat_map do |name|
+        [
+          create_getter_method(name.to_s, sig, visibility, loc, comments),
+          create_setter_method(name.to_s, sig, attribute_type, visibility, loc, comments),
+        ]
+      end
+    end
+  end
+
+  class AttrReader
+    sig { override.returns(T::Array[Method]) }
+    def convert_to_methods
+      sig, _ = parse_sig
+
+      names.map { |name| create_getter_method(name.to_s, sig, visibility, loc, comments) }
+    end
+  end
+
+  class AttrWriter
+    sig { override.returns(T::Array[Method]) }
+    def convert_to_methods
+      sig, attribute_type = parse_sig
+
+      names.map { |name| create_setter_method(name.to_s, sig, attribute_type, visibility, loc, comments) }
+    end
+  end
+end