Modify YardDoc listener to create RBS signatures

It identifies RBS signatures from method comments exported by gems.

Author: KaanOzkan

lib/tapioca/gem/listeners/yard_doc.rb

@@ -23,6 +23,8 @@ class YardDoc < Base
 
         IGNORED_SIG_TAGS = T.let(["param", "return"], T::Array[String])
 
+        RBS_SIGNATURE_PREFIX = T.let(":", String)
+
         #: (Pipeline pipeline) -> void
         def initialize(pipeline)
           YARD::Registry.clear
@@ -64,7 +66,13 @@ def documentation_comments(name, sigs: [])
 
           comments = docstring.lines
             .reject { |line| IGNORED_COMMENTS.any? { |comment| line.include?(comment) } }
-            .map! { |line| RBI::Comment.new(line) }
+            .map! do |line|
+              if line.strip.start_with?(RBS_SIGNATURE_PREFIX)
+                RBI::RBSSig.new(line[1..])
+              else
+                RBI::Comment.new(line)
+              end
+            end
 
           tags = yard_docs.tags
           tags.reject! { |tag| IGNORED_SIG_TAGS.include?(tag.tag_name) } unless sigs.empty?

spec/tapioca/gem/pipeline_spec.rb

@@ -4542,6 +4542,32 @@ def foo; end
       assert_equal(output, compiled)
     end
 
+    it "compiles RBS signatures" do
+      add_ruby_file("foo.rb", <<~RUBY)
+        class Foo
+          #: -> String
+          def foo; end
+
+          #: -> Integer
+          def self.bar; end
+        end
+      RUBY
+
+      output = template(<<~RBI)
+        class Foo
+          #: -> String
+          def foo; end
+
+          class << self
+            #: -> Integer
+            def bar; end
+          end
+        end
+      RBI
+
+      assert_equal(output, compile(include_doc: true))
+    end
+
     it "compiles constants with nil values" do
       add_ruby_file("foo.rb", <<~RUBY)
         class Foo