Preserve inline comments inside sig blocks during RBS translation

lib/spoom/sorbet/translate/sorbet_sigs_to_rbs_comments.rb

@@ -78,6 +78,7 @@ def visit_def_node(node)
             out = rbs_print(node.location.start_column) do |printer|
               printer.print_method_sig(rbi_node, sig)
             end
+            out = add_sig_comments(node, out)
             @rewriter << Source::Replace.new(node.location.start_offset, node.location.end_offset, out)
           end
 
@@ -179,7 +180,7 @@ def visit_scope(node, &block)
         def visit_sig(node)
           return unless sorbet_sig?(node)
 
-          builder = RBI::Parser::SigBuilder.new(@ruby_contents, file: @file)
+          builder = RBI::Parser::SigBuilder.new(@ruby_contents, comments_by_line: @comments_by_line, file: @file)
           builder.current.loc = node.location
           builder.visit_call_node(node)
           builder.current.comments = []
@@ -207,6 +208,7 @@ def visit_attr(node)
             out = rbs_print(node.location.start_column) do |printer|
               printer.print_attr_sig(rbi_node, sig)
             end
+            out = add_sig_comments(node, out)
             @rewriter << Source::Replace.new(node.location.start_offset, node.location.end_offset, out)
           end
         end
@@ -379,6 +381,20 @@ def delete_extend_t_generics
           @extend_t_generics.clear
         end
 
+        # `RBI::SigBuilder` consumes parameter comments and attaches them to `RBI::SigParam`.
+        # Preserve any other comments left inside the sig body, like comments before `returns`.
+        #: (Prism::CallNode, String) -> String
+        def add_sig_comments(sig_node, out)
+          comments = @comments_by_line.values.select do |comment|
+            comment.location.start_offset > sig_node.location.start_offset &&
+              comment.location.end_offset <= sig_node.location.end_offset
+          end
+          return out if comments.empty?
+
+          indent = " " * sig_node.location.start_column
+          comments.map { |comment| "#{comment.slice}\n#{indent}" }.join + out
+        end
+
         # Collects the last signatures visited and clears the current list
         #: -> Array[[Prism::CallNode, RBI::Sig]]
         def collect_last_sigs

lib/spoom/sorbet/translate/translator.rb

@@ -22,6 +22,7 @@ def initialize(ruby_contents, file:)
           node, comments = Spoom.parse_ruby(ruby_contents, file: file)
           @node = node #: Prism::Node
           @comments = comments #: Array[Prism::Comment]
+          @comments_by_line = comments.to_h { |comment| [comment.location.start_line, comment] } #: Hash[Integer, Prism::Comment]
           @ruby_bytes = ruby_contents.bytes #: Array[Integer]
           @rewriter = Spoom::Source::Rewriter.new #: Source::Rewriter
         end

rbi/spoom.rbi

@@ -3023,6 +3023,9 @@ class Spoom::Sorbet::Translate::SorbetSigsToRBSComments < ::Spoom::Sorbet::Trans
 
   private
 
+  sig { params(sig_node: ::Prism::CallNode, out: ::String).returns(::String) }
+  def add_sig_comments(sig_node, out); end
+
   sig do
     params(
       parent: T.any(::Prism::ClassNode, ::Prism::ModuleNode, ::Prism::SingletonClassNode),

test/spoom/sorbet/translate/sorbet_sigs_to_rbs_comments_test.rb

@@ -466,6 +466,64 @@ def foo(param1:, param2:); end
           RBS
         end
 
+        def test_translate_to_rbs_sig_with_inline_param_comments
+          contents = <<~RB
+            sig do
+              params(
+                # First param
+                a: Integer,
+                # Second param
+                b: String
+              ).void
+            end
+            def foo(a, b); end
+
+            sig do
+              # A comment
+              returns(Integer)
+            end
+            attr_reader :x
+          RB
+
+          assert_equal(<<~RBS, sorbet_sigs_to_rbs_comments(contents))
+            #: (
+            #|   # First param
+            #|   Integer a,
+            #|   # Second param
+            #|   String b
+            #| ) -> void
+            def foo(a, b); end
+
+            # A comment
+            #: Integer
+            attr_reader :x
+          RBS
+        end
+
+        def test_translate_to_rbs_sig_with_inline_param_comments_indented
+          contents = <<~RB
+            class Foo
+              sig do
+                params(
+                  # First param
+                  a: Integer
+                ).void
+              end
+              def foo(a); end
+            end
+          RB
+
+          assert_equal(<<~RBS, sorbet_sigs_to_rbs_comments(contents))
+            class Foo
+              #: (
+              #|   # First param
+              #|   Integer a
+              #| ) -> void
+              def foo(a); end
+            end
+          RBS
+        end
+
         def test_translate_to_rbs_defs_within_send
           contents = <<~RB
             sig { void }