Introduce TranslateSigs to translate RBI sigs to RBS sigs in a file

Signed-off-by: Alexandre Terrasa <alexandre.terrasa@shopify.com>

lib/spoom/sorbet/translate_sigs.rb

@@ -0,0 +1,137 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "rbi"
+
+module Spoom
+  module Sorbet
+    class TranslateSigs
+      class << self
+        extend T::Sig
+
+        sig { params(ruby_contents: String).returns(String) }
+        def rbi_to_rbs(ruby_contents)
+          ruby_contents = ruby_contents.dup
+
+          tree = RBI::Parser.parse_string(ruby_contents)
+
+          translator = RBI2RBS.new
+          translator.visit(tree)
+          sigs = translator.sigs.sort_by { |sig, _rbs_string| -T.must(sig.loc&.begin_line) }
+
+          sigs.each do |sig, rbs_string|
+            scanner = Scanner.new(ruby_contents)
+            start_index = scanner.find_char_position(
+              line: T.must(sig.loc&.begin_line) - 1,
+              character: T.must(sig.loc).begin_column,
+            )
+            end_index = scanner.find_char_position(
+              line: sig.loc&.end_line&.-(1),
+              character: T.must(sig.loc).end_column,
+            )
+            ruby_contents[start_index...end_index] = rbs_string
+          end
+
+          ruby_contents
+        end
+      end
+
+      class RBI2RBS < RBI::Visitor
+        extend T::Sig
+
+        sig { returns(T::Array[[RBI::Sig, String]]) }
+        attr_reader :sigs
+
+        sig { void }
+        def initialize
+          super
+          @sigs = T.let([], T::Array[[RBI::Sig, String]])
+        end
+
+        sig { override.params(node: T.nilable(RBI::Node)).void }
+        def visit(node)
+          return unless node
+
+          case node
+          when RBI::Method
+            translate_method_sigs(node)
+          when RBI::Attr
+            translate_attr_sigs(node)
+          when RBI::Tree
+            visit_all(node.nodes)
+          end
+
+          super
+        end
+
+        private
+
+        sig { params(node: RBI::Method).void }
+        def translate_method_sigs(node)
+          node.sigs.each do |sig|
+            out = StringIO.new
+            p = RBI::RBSPrinter.new(out: out, indent: sig.loc&.begin_column)
+
+            if node.sigs.any?(&:is_abstract)
+              p.printn("# @abstract")
+              p.printt
+            end
+
+            if node.sigs.any?(&:is_override)
+              p.printn("# @override")
+              p.printt
+            end
+
+            if node.sigs.any?(&:is_overridable)
+              p.printn("# @overridable")
+              p.printt
+            end
+
+            p.print("#: ")
+            p.send(:print_method_sig, node, sig)
+
+            @sigs << [sig, out.string]
+          end
+        end
+
+        sig { params(node: RBI::Attr).void }
+        def translate_attr_sigs(node)
+          node.sigs.each do |sig|
+            out = StringIO.new
+            p = RBI::RBSPrinter.new(out: out)
+            p.print_attr_sig(node, sig)
+            @sigs << [sig, "#: #{out.string}"]
+          end
+        end
+      end
+
+      # From https://github.com/Shopify/ruby-lsp/blob/9154bfc6ef/lib/ruby_lsp/document.rb#L127
+      class Scanner
+        extend T::Sig
+
+        LINE_BREAK = T.let(0x0A, Integer)
+
+        sig { params(source: String).void }
+        def initialize(source)
+          @current_line = T.let(0, Integer)
+          @pos = T.let(0, Integer)
+          @source = T.let(source.bytes, T::Array[Integer])
+        end
+
+        # Finds the character index inside the source string for a given line and column
+        sig { params(position: T::Hash[Symbol, T.untyped]).returns(Integer) }
+        def find_char_position(position)
+          # Find the character index for the beginning of the requested line
+          until @current_line == position[:line]
+            @pos += 1 until LINE_BREAK == @source[@pos]
+            @pos += 1
+            @current_line += 1
+          end
+
+          # The final position is the beginning of the line plus the requested column
+          @pos + position[:character]
+        end
+      end
+    end
+  end
+end

test/spoom/sorbet/translate_sigs_test.rb

@@ -0,0 +1,123 @@
+# typed: true
+# frozen_string_literal: true
+
+require "test_helper"
+
+module Spoom
+  module Sorbet
+    class TranslateSigsTest < Minitest::Test
+      def test_empty
+        contents = ""
+        assert_equal(contents, TranslateSigs.rbi_to_rbs(contents))
+      end
+
+      def test_no_sigs
+        contents = <<~RBI
+          class A
+            def foo; end
+          end
+        RBI
+
+        assert_equal(contents, TranslateSigs.rbi_to_rbs(contents))
+      end
+
+      def test_top_level_sig
+        contents = <<~RBI
+          # typed: true
+
+          sig { params(a: Integer, b: Integer).returns(Integer) }
+          def foo(a, b)
+            a + b
+          end
+        RBI
+
+        assert_equal(<<~RBS, TranslateSigs.rbi_to_rbs(contents))
+          # typed: true
+
+          #: (Integer a, Integer b) -> Integer
+          def foo(a, b)
+            a + b
+          end
+        RBS
+      end
+
+      def test_method_sigs
+        contents = <<~RBI
+          class A
+            sig { params(a: Integer).void }
+            def initialize(a)
+              @a = a
+            end
+
+            sig { returns(Integer) }
+            def a
+              @a
+            end
+          end
+        RBI
+
+        assert_equal(<<~RBS, TranslateSigs.rbi_to_rbs(contents))
+          class A
+            #: (Integer a) -> void
+            def initialize(a)
+              @a = a
+            end
+
+            #: -> Integer
+            def a
+              @a
+            end
+          end
+        RBS
+      end
+
+      def test_singleton_method_sigs
+        contents = <<~RBI
+          class A
+            sig { returns(Integer) }
+            def self.foo
+              42
+            end
+          end
+        RBI
+
+        assert_equal(<<~RBS, TranslateSigs.rbi_to_rbs(contents))
+          class A
+            #: -> Integer
+            def self.foo
+              42
+            end
+          end
+        RBS
+      end
+
+      def test_attr_sigs
+        contents = <<~RBI
+          class A
+            sig { returns(Integer) }
+            attr_accessor :a
+
+            sig { returns(Integer) }
+            attr_reader :b, :c
+
+            sig { params(d: Integer).void }
+            attr_writer :d, :e
+          end
+        RBI
+
+        assert_equal(<<~RBS, TranslateSigs.rbi_to_rbs(contents))
+          class A
+            #: Integer
+            attr_accessor :a
+
+            #: Integer
+            attr_reader :b, :c
+
+            #: Integer
+            attr_writer :d, :e
+          end
+        RBS
+      end
+    end
+  end
+end