Parse optional in first field when punned.

Fixes #583

Author: cristianoc

src/res_core.ml

@@ -2676,6 +2676,7 @@ and parseJsxChildren p =
 and parseBracedOrRecordExpr p =
   let startPos = p.Parser.startPos in
   Parser.expect Lbrace p;
+  let attrsForFields = parseAttributesForFields p in
   match p.Parser.token with
   | Rbrace ->
     Parser.err p (Diagnostics.unexpected Rbrace p.breadcrumbs);
@@ -2752,7 +2753,16 @@ and parseBracedOrRecordExpr p =
           | _ -> valueOrConstructor
         in
         let expr =
-          parseRecordExpr ~startPos [(pathIdent, valueOrConstructor)] p
+          parseRecordExpr ~startPos
+            [
+              ( pathIdent,
+                {
+                  valueOrConstructor with
+                  pexp_attributes =
+                    attrsForFields @ valueOrConstructor.pexp_attributes;
+                } );
+            ]
+            p
         in
         Parser.expect Rbrace p;
         expr
@@ -6253,9 +6263,29 @@ and parseAttribute p =
           ] )
   | _ -> None
 
+and parseAttributeForFields p =
+  let isAttributeForField p =
+    Parser.lookahead p (function state ->
+        (Parser.next state;
+         match state.token with
+         | Lident ident -> ident = "optional"
+         | _ -> false))
+  in
+  match p.Parser.token with
+  | At when isAttributeForField p ->
+    let startPos = p.startPos in
+    Parser.next p;
+    let attrId = parseAttributeId ~startPos p in
+    let payload = parsePayload p in
+    Some (attrId, payload)
+  | _ -> None
+
 and parseAttributes p =
   parseRegion p ~grammar:Grammar.Attribute ~f:parseAttribute
 
+and parseAttributesForFields p =
+  parseRegion p ~grammar:Grammar.Attribute ~f:parseAttributeForFields
+
 (*
  * standalone-attribute ::=
  *  | @@ atribute-id

tests/parsing/grammar/expressions/expected/record.res.txt

@@ -19,6 +19,7 @@ let r =
     z = ((None)[@optional ])
   }
 let z name = { name = ((name)[@optional ]); x = 3 }
+let z name = { name = ((name)[@optional ]); x = 3 }
 let z name = { name; x = ((x)[@optional ]) }
 let _ =
   match z with

tests/parsing/grammar/expressions/record.res

@@ -28,7 +28,7 @@ let r = {x: @optional None, y: @optional None, z: @optional None}
 
 let z = name => { name : @optional name, x: 3}
 
-// let z = name => { @optional name, x: 3}
+let z = name => { @optional name, x: 3}
 
 let z = name => { name, @optional x }
 

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

@@ -80,7 +80,7 @@ let z = name => {@optional name, x: 3}
 
 let z = name => {@optional name, x: 3}
 
-// let z = name => { @optional name, x: 3}
+let z = name => {name, @optional x}
 
 let _ = switch z {
 | {x: @optional None, y: @optional None, z: @optional None} => 11

tests/printer/expr/record.res

@@ -68,9 +68,9 @@ let r = {x: @optional None, y: @optional None, z: @optional None}
 
 let z = name => { name : @optional name, x: 3}
 
-let z = name => { name : @optional name, x: 3}
+let z = name => { @optional name, x: 3}
 
-// let z = name => { @optional name, x: 3}
+let z = name => { name, @optional x }
 
 let _ = switch z {
   | {x: @optional None, y: @optional None, z: @optional None} => 11