Fix inside comment printing for empty dict (#7654)

* Remove trailing comma in empty dict and print inside comment

* Remove extra line

* Add test

* Update CHANGELOG

* Don't use List.is_empty

Author: shulhi

CHANGELOG.md

@@ -36,6 +36,7 @@
 - Fix `typeof` parens on functions. https://github.com/rescript-lang/rescript/pull/7643
 - Rewatch: Add --dev flag to clean command. https://github.com/rescript-lang/rescript/pull/7622
 - Rewatch: Use root package suffix in clean log messages. https://github.com/rescript-lang/rescript/pull/7648
+- Fix inside comment printing for empty dict. https://github.com/rescript-lang/rescript/pull/7654
 
 # 12.0.0-beta.1
 

compiler/syntax/src/res_printer.ml

@@ -1512,7 +1512,7 @@ and print_literal_dict_expr ~state (e : Parsetree.expression) cmt_tbl =
          Doc.indent
            (Doc.concat
               [
-                Doc.soft_line;
+                (if rows = [] then Doc.nil else Doc.soft_line);
                 Doc.join
                   ~sep:(Doc.concat [Doc.text ","; Doc.line])
                   (List.map
@@ -1523,8 +1523,8 @@ and print_literal_dict_expr ~state (e : Parsetree.expression) cmt_tbl =
                        print_comments doc cmt_tbl e.pexp_loc)
                      rows);
               ]);
-         Doc.trailing_comma;
-         Doc.soft_line;
+         (if rows = [] then Doc.nil
+          else Doc.concat [Doc.trailing_comma; Doc.soft_line]);
        ])
 
 and print_constructor_declarations ~state ~private_flag
@@ -4225,6 +4225,7 @@ and print_pexp_apply ~state expr cmt_tbl =
     Doc.concat
       [
         Doc.text "dict{";
+        print_comments_inside cmt_tbl expr.pexp_loc;
         print_literal_dict_expr ~state key_values cmt_tbl;
         Doc.rbrace;
       ]

tests/syntax_tests/data/printer/expr/dict.res

@@ -1,6 +1,12 @@
 // empty dict
 let x = dict{}
 
+// empty dict with inside comment
+let x = dict{
+  // inside comment
+
+}
+
 // one value
 let x = dict{"foo": "bar"}
 

tests/syntax_tests/data/printer/expr/expected/dict.res.txt

@@ -1,6 +1,11 @@
 // empty dict
 let x = dict{}
 
+// empty dict with inside comment
+let x = dict{
+  // inside comment
+}
+
 // one value
 let x = dict{"foo": "bar"}