Print punned fields (#480)

* Print punned fields

* Avoid List.length

* Add test cases for punning + comments

Author: cknitt

src/res_printer.ml

@@ -2807,6 +2807,10 @@ and printExpression (e : Parsetree.expression) cmtTbl =
     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;
@@ -2815,7 +2819,7 @@ and printExpression (e : Parsetree.expression) cmtTbl =
             Doc.softLine;
             spread;
             Doc.join ~sep:(Doc.concat [Doc.text ","; Doc.line])
-              (List.map (fun row -> printRecordRow row cmtTbl) rows)
+              (List.map (fun row -> printRecordRow row cmtTbl punningAllowed) rows)
           ]
         );
         Doc.trailingComma;
@@ -4818,17 +4822,28 @@ and printDirectionFlag flag = match flag with
   | Asttypes.Downto -> Doc.text " downto "
   | Asttypes.Upto -> Doc.text " to "
 
-and printRecordRow (lbl, expr) cmtTbl =
+and printRecordRow (lbl, expr) cmtTbl punningAllowed =
   let cmtLoc = {lbl.loc with loc_end = expr.pexp_loc.loc_end} in
-  let doc = Doc.group (Doc.concat [
-    printLidentPath lbl cmtTbl;
-    Doc.text ": ";
-    (let doc = printExpressionWithComments expr cmtTbl in
-    match Parens.expr expr with
-    | Parens.Parenthesized -> addParens doc
-    | Braced braces -> printBraces doc expr braces
-    | Nothing -> doc);
-  ]) in
+  let doc = Doc.group (
+    match expr.pexp_desc with
+    | Pexp_ident({txt = Lident key; loc = keyLoc}) when (
+      punningAllowed && 
+      Longident.last lbl.txt = key &&
+      lbl.loc.loc_start.pos_cnum == keyLoc.loc_start.pos_cnum
+    ) ->
+      (* print punned field *)
+      printLidentPath lbl cmtTbl;
+    | _ ->
+      Doc.concat [
+      printLidentPath lbl cmtTbl;
+      Doc.text ": ";
+      (let doc = printExpressionWithComments expr cmtTbl in
+      match Parens.expr expr with
+      | Parens.Parenthesized -> addParens doc
+      | Braced braces -> printBraces doc expr braces
+      | Nothing -> doc);
+    ]
+  ) in
   printComments doc cmtTbl cmtLoc
 
 and printBsObjectRow (lbl, expr) cmtTbl =

tests/conversion/reason/expected/bracedJsx.re.txt

@@ -91,7 +91,7 @@ let make = () => {
           ],
         ),
       }
-    | SetValue(input) => {...state, input: input}
+    | SetValue(input) => {...state, input}
     }
   , {history: [], input: ""})
 

tests/conversion/reason/expected/braces.re.txt

@@ -20,5 +20,5 @@ let getDailyNewCases = x =>
   | Pair({prevRecord, record}) =>
     let confirmed = record.confirmed - prevRecord.confirmed
     let deaths = record.deaths - prevRecord.deaths
-    {confirmed: confirmed, deaths: deaths}
+    {confirmed, deaths}
   }

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

@@ -60,7 +60,7 @@ React.useEffect0(() => {
     switch videoContainerRect {
     | Some(videoContainerRect) =>
       let newChapter = ({startTime: percent *. duration}: Video.chapter)
-      {a: a, b: b}->onChange
+      {a, b}->onChange
     | _ => ()
     }
   }}

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

@@ -39,3 +39,35 @@ let user = {
 }
 // braced + constrained expr
 let user = {name: {(ceo.name: string)}}
+
+// Punning
+let r = {a} // actually not a record, just an expression in braces
+let r = {a, b}
+let r = {a, b, c: 42}
+let r = {A.a, b}
+let r = {A.a: a, b}
+let r = {a: a, b}
+let r = {a, b: b}
+
+// Punning + comments
+let r = {
+  // a
+  a,
+  // b
+  b,
+}
+let r = {
+  a, // a
+  b, // b
+}
+let r = {
+  /* a */
+  a,
+  /* b */
+  b,
+}
+let r = {
+  a /* a */,
+  b /* b */,
+}
+let r = {a /* a */, b /* b */}

tests/printer/expr/record.res

@@ -28,3 +28,36 @@ let user = {name: {
 }}
 // braced + constrained expr
 let user = {name: {(ceo.name: string)}}
+
+
+// Punning
+let r = {a} // actually not a record, just an expression in braces
+let r = {a, b}
+let r = {a, b, c: 42}
+let r = {A.a, b}
+let r = {A.a: a, b}
+let r = {a: a, b}
+let r = {a, b: b}
+
+// Punning + comments
+let r = {
+  // a
+  a,
+  // b
+  b,
+}
+let r = {
+  a, // a
+  b, // b
+}
+let r = {
+  /* a */
+  a,
+  /* b */
+  b,
+}
+let r = {
+  a /* a */,
+  b /* b */,
+}
+let r = {a /* a */, b /* b */}