Fix expr record field completion in existing records (#997)

* fix case in expr record field completion where the record body context was not picked up

* fix case when cursor is at start of record body but in no field

* changelog

* dont use empty line

CHANGELOG.md

@@ -19,6 +19,7 @@
 - Fix JSX prop special case in end of JSX element. https://github.com/rescript-lang/rescript-vscode/pull/984
 - preserve URI format in canonicalizeUri. https://github.com/rescript-lang/rescript-vscode/pull/990
 - Remove workaround for canonicalize function in tests https://github.com/rescript-lang/rescript-vscode/pull/992
+- Get completions for writing new field names in a record body expressions in more cases. https://github.com/rescript-lang/rescript-vscode/pull/997
 
 #### :nail_care: Polish
 

analysis/src/CompletionExpressions.ml

@@ -84,6 +84,10 @@ let rec traverseExpr (exp : Parsetree.expression) ~exprPath ~pos
         (* An expression hole means for example `{someField: <com>}`. We want to complete for the type of `someField`.  *)
         someIfHasCursor
           ("", [Completable.NFollowRecordField {fieldName = fname}] @ exprPath)
+      | Pexp_ident {txt = Lident txt} when fname = txt ->
+        (* This is a heuristic for catching writing field names. ReScript has punning for record fields, but the AST doesn't,
+           so punning is represented as the record field name and identifier being the same: {someField}. *)
+        someIfHasCursor (txt, [Completable.NRecordBody {seenFields}] @ exprPath)
       | Pexp_ident {txt = Lident txt} ->
         (* A var means `{someField: s}` or similar. Complete for identifiers or values. *)
         someIfHasCursor (txt, exprPath)
@@ -94,12 +98,21 @@ let rec traverseExpr (exp : Parsetree.expression) ~exprPath ~pos
                ([Completable.NFollowRecordField {fieldName = fname}] @ exprPath)
       )
     | None, None -> (
+      if Debug.verbose () then (
+        Printf.printf "[traverse_expr] No field with cursor and no expr hole.\n";
+
+        match firstCharBeforeCursorNoWhite with
+        | None -> ()
+        | Some c ->
+          Printf.printf "[traverse_expr] firstCharBeforeCursorNoWhite: %c.\n" c);
+
       (* Figure out if we're completing for a new field.
          If the cursor is inside of the record body, but no field has the cursor,
          and there's no pattern hole. Check the first char to the left of the cursor,
-         ignoring white space. If that's a comma, we assume you're completing for a new field. *)
+         ignoring white space. If that's a comma or {, we assume you're completing for a new field,
+         since you're either between 2 fields (comma to the left) or at the start of the record ({). *)
       match firstCharBeforeCursorNoWhite with
-      | Some ',' ->
+      | Some (',' | '{') ->
         someIfHasCursor ("", [Completable.NRecordBody {seenFields}] @ exprPath)
       | _ -> None))
   | Pexp_construct

analysis/tests/src/CompletionExpressions.res

@@ -362,3 +362,26 @@ let someTyp: someTyp = {test: true}
 
 // switch someTyp. { | _ => () }
 //                ^com
+
+type config = {
+  includeName: bool,
+  operator?: [#"and" | #or],
+  showMore: bool,
+}
+
+type hookReturn = {name: string}
+
+let hook = (config: config) => {
+  ignore(config)
+  {
+    name: "tester",
+  }
+}
+
+let {name} = hook({
+  //                  ^com
+  // ope
+  //    ^com
+  includeName: true,
+  showMore: true,
+})

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

@@ -1423,3 +1423,39 @@ Path someTyp
     "documentation": {"kind": "markdown", "value": "```rescript\ntest: bool\n```\n\n```rescript\ntype someTyp = {test: bool}\n```"}
   }]
 
+Complete src/CompletionExpressions.res 380:22
+posCursor:[380:22] posNoWhite:[380:18] Found expr:[380:13->386:2]
+Pexp_apply ...[380:13->380:17] (...[380:18->386:1])
+Completable: Cexpression CArgument Value[hook]($0)->recordBody
+Raw opens: 1 CompletionSupport.place holder
+Package opens Pervasives.JsxModules.place holder
+Resolved opens 2 pervasives CompletionSupport.res
+ContextPath CArgument Value[hook]($0)
+ContextPath Value[hook]
+Path hook
+[{
+    "label": "operator",
+    "kind": 5,
+    "tags": [],
+    "detail": "[#\"and\" | #or]",
+    "documentation": {"kind": "markdown", "value": "```rescript\noperator?: [#\"and\" | #or]\n```\n\n```rescript\ntype config = {includeName: bool, operator: option<[#\"and\" | #or]>, showMore: bool}\n```"}
+  }]
+
+Complete src/CompletionExpressions.res 382:8
+posCursor:[382:8] posNoWhite:[382:7] Found expr:[380:13->386:2]
+Pexp_apply ...[380:13->380:17] (...[380:18->386:1])
+Completable: Cexpression CArgument Value[hook]($0)=ope->recordBody
+Raw opens: 1 CompletionSupport.place holder
+Package opens Pervasives.JsxModules.place holder
+Resolved opens 2 pervasives CompletionSupport.res
+ContextPath CArgument Value[hook]($0)
+ContextPath Value[hook]
+Path hook
+[{
+    "label": "operator",
+    "kind": 5,
+    "tags": [],
+    "detail": "[#\"and\" | #or]",
+    "documentation": {"kind": "markdown", "value": "```rescript\noperator?: [#\"and\" | #or]\n```\n\n```rescript\ntype config = {includeName: bool, operator: option<[#\"and\" | #or]>, showMore: bool}\n```"}
+  }]
+