Unify comment formatting inside the empty blocks

src/res_comments_table.ml

@@ -692,9 +692,12 @@ and walkTypeDeclaration (td : Parsetree.type_declaration) t comments =
     | Ptype_abstract | Ptype_open -> rest
     | Ptype_record labelDeclarations ->
       let () =
-        walkList
-          (labelDeclarations |> List.map (fun ld -> LabelDeclaration ld))
-          t rest
+        if List.length labelDeclarations = 0 then
+          attach t.inside td.ptype_loc rest
+        else
+          walkList
+            (labelDeclarations |> List.map (fun ld -> LabelDeclaration ld))
+            t rest
       in
       []
     | Ptype_variant constructorDeclarations ->
@@ -1023,22 +1026,26 @@ and walkExpression expr t comments =
   | Pexp_array exprs | Pexp_tuple exprs ->
     walkList (exprs |> List.map (fun e -> Expression e)) t comments
   | Pexp_record (rows, spreadExpr) ->
-    let comments =
-      match spreadExpr with
-      | None -> comments
-      | Some expr ->
-        let leading, inside, trailing = partitionByLoc comments expr.pexp_loc in
-        attach t.leading expr.pexp_loc leading;
-        walkExpression expr t inside;
-        let afterExpr, rest =
-          partitionAdjacentTrailing expr.pexp_loc trailing
-        in
-        attach t.trailing expr.pexp_loc afterExpr;
-        rest
-    in
-    walkList
-      (rows |> List.map (fun (li, e) -> ExprRecordRow (li, e)))
-      t comments
+    if List.length rows = 0 then attach t.inside expr.pexp_loc comments
+    else
+      let comments =
+        match spreadExpr with
+        | None -> comments
+        | Some expr ->
+          let leading, inside, trailing =
+            partitionByLoc comments expr.pexp_loc
+          in
+          attach t.leading expr.pexp_loc leading;
+          walkExpression expr t inside;
+          let afterExpr, rest =
+            partitionAdjacentTrailing expr.pexp_loc trailing
+          in
+          attach t.trailing expr.pexp_loc afterExpr;
+          rest
+      in
+      walkList
+        (rows |> List.map (fun (li, e) -> ExprRecordRow (li, e)))
+        t comments
   | Pexp_field (expr, longident) ->
     let leading, inside, trailing = partitionByLoc comments expr.pexp_loc in
     let trailing =

src/res_printer.ml

@@ -1231,23 +1231,34 @@ and printTypeDeclaration2 ~customLayout ~recFlag
           Doc.text "..";
         ]
     | Ptype_record lds ->
-      let manifest =
-        match td.ptype_manifest with
-        | None -> Doc.nil
-        | Some typ ->
-          Doc.concat
-            [
-              Doc.concat [Doc.space; Doc.text equalSign; Doc.space];
-              printTypExpr ~customLayout typ cmtTbl;
-            ]
-      in
-      Doc.concat
-        [
-          manifest;
-          Doc.concat [Doc.space; Doc.text equalSign; Doc.space];
-          printPrivateFlag td.ptype_private;
-          printRecordDeclaration ~customLayout lds cmtTbl;
-        ]
+      if List.length lds = 0 then
+        Doc.concat
+          [
+            Doc.space;
+            Doc.text equalSign;
+            Doc.space;
+            Doc.lbrace;
+            printCommentsInside cmtTbl td.ptype_loc;
+            Doc.rbrace;
+          ]
+      else
+        let manifest =
+          match td.ptype_manifest with
+          | None -> Doc.nil
+          | Some typ ->
+            Doc.concat
+              [
+                Doc.concat [Doc.space; Doc.text equalSign; Doc.space];
+                printTypExpr ~customLayout typ cmtTbl;
+              ]
+        in
+        Doc.concat
+          [
+            manifest;
+            Doc.concat [Doc.space; Doc.text equalSign; Doc.space];
+            printPrivateFlag td.ptype_private;
+            printRecordDeclaration ~customLayout lds cmtTbl;
+          ]
     | Ptype_variant cds ->
       let manifest =
         match td.ptype_manifest with
@@ -2846,59 +2857,63 @@ and printExpression ~customLayout (e : Parsetree.expression) cmtTbl =
       in
       Doc.group (Doc.concat [variantName; args])
     | Pexp_record (rows, spreadExpr) ->
-      let spread =
-        match spreadExpr with
-        | None -> Doc.nil
-        | Some expr ->
-          Doc.concat
-            [
-              Doc.dotdotdot;
-              (let doc =
-                 printExpressionWithComments ~customLayout expr cmtTbl
-               in
-               match Parens.expr expr with
-               | Parens.Parenthesized -> addParens doc
-               | Braced braces -> printBraces doc expr braces
-               | Nothing -> doc);
-              Doc.comma;
-              Doc.line;
-            ]
-      in
-      (* If the record is written over multiple lines, break automatically
-       * `let x = {a: 1, b: 3}` -> same line, break when line-width exceeded
-       * `let x = {
-       *   a: 1,
-       *   b: 2,
-       *  }` -> record is written on multiple lines, break the group *)
-      let forceBreak =
-        e.pexp_loc.loc_start.pos_lnum < e.pexp_loc.loc_end.pos_lnum
-      in
-      let punningAllowed =
-        match (spreadExpr, rows) with
-        | None, [_] -> false (* disallow punning for single-element records *)
-        | _ -> true
-      in
-      Doc.breakableGroup ~forceBreak
-        (Doc.concat
-           [
-             Doc.lbrace;
-             Doc.indent
-               (Doc.concat
-                  [
-                    Doc.softLine;
-                    spread;
-                    Doc.join
-                      ~sep:(Doc.concat [Doc.text ","; Doc.line])
-                      (List.map
-                         (fun row ->
-                           printExpressionRecordRow ~customLayout row cmtTbl
-                             punningAllowed)
-                         rows);
-                  ]);
-             Doc.trailingComma;
-             Doc.softLine;
-             Doc.rbrace;
-           ])
+      if List.length rows = 0 then
+        Doc.concat
+          [Doc.lbrace; printCommentsInside cmtTbl e.pexp_loc; Doc.rbrace]
+      else
+        let spread =
+          match spreadExpr with
+          | None -> Doc.nil
+          | Some expr ->
+            Doc.concat
+              [
+                Doc.dotdotdot;
+                (let doc =
+                   printExpressionWithComments ~customLayout expr cmtTbl
+                 in
+                 match Parens.expr expr with
+                 | Parens.Parenthesized -> addParens doc
+                 | Braced braces -> printBraces doc expr braces
+                 | Nothing -> doc);
+                Doc.comma;
+                Doc.line;
+              ]
+        in
+        (* If the record is written over multiple lines, break automatically
+         * `let x = {a: 1, b: 3}` -> same line, break when line-width exceeded
+         * `let x = {
+         *   a: 1,
+         *   b: 2,
+         *  }` -> record is written on multiple lines, break the group *)
+        let forceBreak =
+          e.pexp_loc.loc_start.pos_lnum < e.pexp_loc.loc_end.pos_lnum
+        in
+        let punningAllowed =
+          match (spreadExpr, rows) with
+          | None, [_] -> false (* disallow punning for single-element records *)
+          | _ -> true
+        in
+        Doc.breakableGroup ~forceBreak
+          (Doc.concat
+             [
+               Doc.lbrace;
+               Doc.indent
+                 (Doc.concat
+                    [
+                      Doc.softLine;
+                      spread;
+                      Doc.join
+                        ~sep:(Doc.concat [Doc.text ","; Doc.line])
+                        (List.map
+                           (fun row ->
+                             printExpressionRecordRow ~customLayout row cmtTbl
+                               punningAllowed)
+                           rows);
+                    ]);
+               Doc.trailingComma;
+               Doc.softLine;
+               Doc.rbrace;
+             ])
     | Pexp_extension extension -> (
       match extension with
       | ( {txt = "bs.obj" | "obj"},

tests/printer/comments/expected/expr.res.txt

@@ -107,6 +107,11 @@ let user = /* before */ {
   /* c4 */ age /* c5 */: /* c6 */ 31 /* c7 */,
 } // after
 
+// Pexp_record with empty record
+let user = /* before */ {/* comment1 */
+// comment2
+} // after
+
 // bs object sugar
 let user = /* before */ {
   // above name

tests/printer/comments/expected/typexpr.res.txt

@@ -28,6 +28,10 @@ type t = /* c0 */ string /* c1 */ as 'x // after
 // Ptyp_poly
 type fn = {f: /* c0 */ 'a /* c1 */ 'b /* c2 */. /* c3 */ string /* c4 */}
 
+type fn = {/* comment1 */
+// comment2
+}
+
 // Ptyp_arrow
 type add = /* before */ (
   /* c0 */ int /* c1 */,

tests/printer/comments/expr.res

@@ -105,6 +105,11 @@ let user = /* before */ {
   /* c4 */ age /* c5 */ : /* c6 */ 31 /* c7 */,
 } // after
 
+// Pexp_record with empty record
+let user = /* before */ {
+  /* comment1 */
+  // comment2
+} // after
 
 // bs object sugar
 let user = /* before */ {

tests/printer/comments/typexpr.res

@@ -28,6 +28,11 @@ type fn = {
   f: /* c0 */ 'a /* c1 */ 'b /* c2*/ . /* c3 */ string /* c4 */
 }
 
+type fn = {
+  /* comment1 */
+  // comment2
+}
+
 // Ptyp_arrow
 type add = /* before */ ( /* c0 */ int /* c1 */, /* c2 */ int /* c3 */) => /* before return */ int /* after */
 type add = /* before */ ( /* c0 */ ~a:int /* c1 */, /* c2 */ ~b:int /* c3 */) => /* before return */ int /* after */