handle empty let assignments with constraints

Author: zth

analysis/src/CompletionBackEndRevamped.ml

@@ -18,9 +18,14 @@ let findRecordField ~env ~package ~fieldName typ =
   | Some (_recordEnv, fields, _decl) ->
     fields |> List.find_opt (fun (field : field) -> field.fname.txt = fieldName)
 
-let completeEmptyPattern ~env ~package typ =
+type patternOrExpr = Pattern | Expr
+let completeEmpty ~(mode : patternOrExpr) ~env ~package typ =
+  ignore mode;
   match TypeUtils.extractType ~env ~package typ with
-  | None -> []
+  | None ->
+    if Debug.verbose () then
+      print_endline "⚠️ Could not extract completable type";
+    []
   | Some (completionType, typeArgContext) -> (
     (* Fill this out with the different completions *)
     match completionType with
@@ -62,22 +67,27 @@ let processCompletable ~debug ~full ~scope ~env ~pos
   match completable with
   | Cexpression {kind; typeLoc} -> (
     match TypeUtils.findTypeViaLoc typeLoc ~full ~debug with
-    | None -> []
+    | None ->
+      if Debug.verbose () then print_endline "⚠️ No type found for loc";
+      []
     | Some typ -> (
+      if Debug.verbose () then
+        print_endline ("✅ Found type at loc:" ^ Shared.typeToString typ);
       match kind with
+      | Empty -> completeEmpty ~mode:Expr ~env ~package typ
       | Field {hint} -> findFields ~env ~package ~hint typ))
   | Cpattern {kind; typeLoc} -> (
     match TypeUtils.findTypeViaLoc typeLoc ~full ~debug with
     | None -> []
     | Some typ -> (
       match kind with
-      | Empty -> completeEmptyPattern ~env ~package typ
+      | Empty -> completeEmpty ~mode:Pattern ~env ~package typ
       | Field {hint; seenFields} ->
         findFields ~env ~package ~hint ~seenFields typ
       | FieldValue {fieldName} -> (
         match findRecordField ~env ~package ~fieldName typ with
         | None -> []
-        | Some field -> completeEmptyPattern ~env ~package field.typ)))
+        | Some field -> completeEmpty ~mode:Pattern ~env ~package field.typ)))
   | Cnone -> []
   | CextensionNode _ -> []
   | Cdecorator prefix ->

analysis/src/CompletionFrontEndRevamped.ml

@@ -165,6 +165,22 @@ let completionWithParser ~currentFile ~debug ~offset ~path ~posCursor text =
   in
   let value_binding (iterator : Ast_iterator.iterator)
       (value_binding : Parsetree.value_binding) =
+    (match value_binding with
+    | {pvb_pat = {ppat_desc = Ppat_constraint (p, _)}; pvb_expr; pvb_loc}
+      when CompletionExpressions.isExprHole pvb_expr
+           && locHasCursor pvb_loc
+           && not (locHasCursor p.ppat_loc) ->
+      (* let x: constraint = <com> *)
+      setResult (Cexpression {kind = Empty; typeLoc = p.ppat_loc; posOfDot})
+    | {pvb_pat; pvb_expr; pvb_loc}
+      when CompletionExpressions.isExprHole pvb_expr
+           && locHasCursor pvb_loc
+           && not (locHasCursor pvb_pat.ppat_loc) ->
+      (* let x= <com> *)
+      (* Unclear if this happens and if we need to care about it. *)
+      setResult
+        (Cexpression {kind = Empty; typeLoc = pvb_pat.ppat_loc; posOfDot})
+    | _ -> ());
     Ast_iterator.default_iterator.value_binding iterator value_binding
   in
   let signature (iterator : Ast_iterator.iterator)

analysis/src/SharedTypes.ml

@@ -801,7 +801,7 @@ module CompletableRevamped = struct
     | ModuleWithImportAttributes of {prefix: string}
     | JsxConfig of {prefix: string}
 
-  type completionExprKind = Field of {hint: string}
+  type completionExprKind = Empty | Field of {hint: string}
 
   type completionPatternKind =
     | Empty

tests/analysis_new_tests/tests/test_files/EmptyExpressions.res

@@ -0,0 +1,3 @@
+// == TEST: Empty let assignment expression, array
+let x: array<string> = 
+//                    ^com

tests/analysis_new_tests/tests/test_files/__snapshots__/EmptyExpressions.res_Empty_let_assignment_expression_array.snap

@@ -0,0 +1,19 @@
+Found Completable: Cexpression at type loc: [1:4->1:5]
+
+  1 │ // Empty let assignment expression, array
+  2 │ let x: array<string> = 
+    │     ‾
+  3 │ //                    ^com
+  4 │ 
+
+[{
+    "label": "[]",
+    "kind": 12,
+    "tags": [],
+    "detail": "array<string>",
+    "documentation": null,
+    "sortText": "A",
+    "insertText": "[$0]",
+    "insertTextFormat": 2
+  }]
+