special handling of optional fields when destructuring

CHANGELOG.md

@@ -36,6 +36,7 @@
 - Improve precision in signature help. You now do not need to type anything into the argument for it to highlight. https://github.com/rescript-lang/rescript-vscode/pull/675
 - Remove redundant function name in signature help, to clean up what's shown to the user some. https://github.com/rescript-lang/rescript-vscode/pull/678
 - Show docstrings in hover for record fields and variant constructors. https://github.com/rescript-lang/rescript-vscode/pull/694
+- The necessary leading `?` is now automatically inserted for optional fields when destructuring records. https://github.com/rescript-lang/rescript-vscode/pull/715
 
 #### :bug: Bug Fix
 

analysis/src/CompletionBackEnd.ml

@@ -1047,10 +1047,10 @@ let printConstructorArgs argsLen ~asSnippet =
   if List.length !args > 0 then "(" ^ (!args |> String.concat ", ") ^ ")"
   else ""
 
-type completionMode = Pattern | Expression
+type completionMode = Pattern of Completable.patternMode | Expression
 
-let rec completeTypedValue (t : SharedTypes.completionType) ~full ~prefix
-    ~completionContext ~mode =
+let rec completeTypedValue ~full ~prefix ~completionContext ~mode
+    (t : SharedTypes.completionType) =
   match t with
   | Tbool env ->
     [
@@ -1142,10 +1142,23 @@ let rec completeTypedValue (t : SharedTypes.completionType) ~full ~prefix
       |> List.filter (fun (field : field) ->
              List.mem field.fname.txt seenFields = false)
       |> List.map (fun (field : field) ->
-             Completion.create field.fname.txt
-               ~kind:
-                 (Field (field, TypeUtils.extractedTypeToString extractedType))
-               ~env)
+             match (field.optional, mode) with
+             | true, Pattern Destructuring ->
+               Completion.create ("?" ^ field.fname.txt)
+                 ~docstring:
+                   [
+                     field.fname.txt
+                     ^ " is an optional field, and needs to be destructured \
+                        using '?'.";
+                   ]
+                 ~kind:
+                   (Field (field, TypeUtils.extractedTypeToString extractedType))
+                 ~env
+             | _ ->
+               Completion.create field.fname.txt
+                 ~kind:
+                   (Field (field, TypeUtils.extractedTypeToString extractedType))
+                 ~env)
       |> filterItems ~prefix
     | None ->
       if prefix = "" then
@@ -1157,7 +1170,7 @@ let rec completeTypedValue (t : SharedTypes.completionType) ~full ~prefix
               (ExtractedType
                  ( extractedType,
                    match mode with
-                   | Pattern -> `Type
+                   | Pattern _ -> `Type
                    | Expression -> `Value ))
             ~env ();
         ]
@@ -1190,7 +1203,7 @@ let rec completeTypedValue (t : SharedTypes.completionType) ~full ~prefix
             (ExtractedType
                ( typ,
                  match mode with
-                 | Pattern -> `Type
+                 | Pattern _ -> `Type
                  | Expression -> `Value ))
           ~env ();
       ]
@@ -1360,7 +1373,7 @@ let rec processCompletable ~debug ~full ~scope ~env ~pos ~forHover
            Utils.startsWith name prefix
            && (forHover || not (List.mem name identsSeen)))
     |> List.map mkLabel
-  | Cpattern {contextPath; prefix; nested; fallback} -> (
+  | Cpattern {contextPath; prefix; nested; fallback; patternMode} -> (
     let fallbackOrEmpty ?items () =
       match (fallback, items) with
       | Some fallback, (None | Some []) ->
@@ -1385,7 +1398,8 @@ let rec processCompletable ~debug ~full ~scope ~env ~pos ~forHover
       | Some (typ, _env, completionContext) ->
         let items =
           typ
-          |> completeTypedValue ~mode:Pattern ~full ~prefix ~completionContext
+          |> completeTypedValue ~mode:(Pattern patternMode) ~full ~prefix
+               ~completionContext
         in
         fallbackOrEmpty ~items ())
     | None -> fallbackOrEmpty ())

analysis/src/CompletionFrontEnd.ml

@@ -317,6 +317,7 @@ let completionWithParser1 ~currentFile ~debug ~offset ~path ~posCursor ~text =
              prefix;
              nested = List.rev nestedPattern;
              fallback = None;
+             patternMode = Default;
            })
     | _ -> ()
   in
@@ -391,6 +392,7 @@ let completionWithParser1 ~currentFile ~debug ~offset ~path ~posCursor ~text =
                  nested = [];
                  prefix = "";
                  fallback = None;
+                 patternMode = Default;
                }))
       | Pexp_match (exp, cases) -> (
         (* If there's more than one case, or the case isn't a pattern hole, figure out if we're completing another
@@ -423,6 +425,7 @@ let completionWithParser1 ~currentFile ~debug ~offset ~path ~posCursor ~text =
                    nested = [];
                    prefix = "";
                    fallback = None;
+                   patternMode = Default;
                  })
           | false, false -> ()))
       | _ -> unsetLookingForPat ()
@@ -524,6 +527,7 @@ let completionWithParser1 ~currentFile ~debug ~offset ~path ~posCursor ~text =
                prefix;
                nested = List.rev nested;
                fallback = None;
+               patternMode = Destructuring;
              })
       | _ -> ())
     | _ -> ());

analysis/src/SharedTypes.ml

@@ -631,6 +631,8 @@ module Completable = struct
       ^ ")"
     | NArray -> "array"
 
+  type patternMode = Default | Destructuring
+
   type t =
     | Cdecorator of string  (** e.g. @module *)
     | CnamedArg of contextPath * string * string list
@@ -648,6 +650,7 @@ module Completable = struct
         contextPath: contextPath;
         nested: nestedPath list;
         prefix: string;
+        patternMode: patternMode;
         fallback: t option;
       }
     | CexhaustiveSwitch of {contextPath: contextPath; exprLoc: Location.t}

analysis/tests/src/Destructuring.res

@@ -19,3 +19,15 @@ let f2 = (x: x) => {
   //      ^com
   ignore(x)
 }
+
+type recordWithOptField = {
+  someField: int,
+  someOptField?: bool
+}
+
+let x: recordWithOptField = {
+  someField: 123
+}
+
+// let {} = x
+//      ^com

analysis/tests/src/expected/Destructuring.res.txt

@@ -58,3 +58,20 @@ Completable: Cpattern Value[x]->recordBody
     "documentation": null
   }]
 
+Complete src/Destructuring.res 31:8
+posCursor:[31:8] posNoWhite:[31:7] Found pattern:[31:7->31:9]
+Completable: Cpattern Value[x]->recordBody
+[{
+    "label": "someField",
+    "kind": 5,
+    "tags": [],
+    "detail": "someField: int\n\nrecordWithOptField",
+    "documentation": null
+  }, {
+    "label": "?someOptField",
+    "kind": 5,
+    "tags": [],
+    "detail": "?someOptField: option<bool>\n\nrecordWithOptField",
+    "documentation": {"kind": "markdown", "value": "someOptField is an optional field, and needs to be destructured using '?'."}
+  }]
+