fix(grainfmt): Handle source files with no code, only comments (#1411)

compiler/src/formatting/format.re

@@ -4199,18 +4199,24 @@ let format_ast =
  print_attributes(attributes);
  };
 
- let top_level_stmts =
- block_item_iterator(
- ~previous=TopOfFile,
- ~get_loc,
- ~print_item,
- ~comments=cleaned_comments,
- ~print_attribute=get_attributes,
- ~original_source,
- parsed_program.statements,
- );
+ // special case where we have no code, we still format the comments
 
- let final_doc = Doc.concat([top_level_stmts, Doc.hardLine]);
+ let final_doc =
+ switch (parsed_program.statements) {
+ | [] => Comment_utils.new_comments_to_docs(cleaned_comments)
+ | _ =>
+ let top_level_stmts =
+ block_item_iterator(
+ ~previous=TopOfFile,
+ ~get_loc,
+ ~print_item,
+ ~comments=cleaned_comments,
+ ~print_attribute=get_attributes,
+ ~original_source,
+ parsed_program.statements,
+ );
+ Doc.concat([top_level_stmts, Doc.hardLine]);
+ };
 
  Doc.toString(~width=80, ~eol, final_doc);
 };

compiler/test/formatter_inputs/only_comments.gr

@@ -0,0 +1,10 @@
+
+
+
+
+ /* this is just a comment */
+
+
+
+
+ // and this too

compiler/test/formatter_outputs/only_comments.gr

@@ -0,0 +1,3 @@
+/* this is just a comment */
+
+// and this too

compiler/test/suites/formatter.re

@@ -47,4 +47,5 @@ describe("formatter", ({test, testSkip}) => {
  assertFormatOutput("patterns", "patterns");
  assertFormatOutput("rationals", "rationals");
  assertFormatOutput("constraints", "constraints");
+ assertFormatOutput("only_comments", "only_comments");
 });