[flow][autocomplete] check enclosing statement when autocompleting er…

…ror suppression in comments

Summary:
Autocomplete offers a special feature of returning an error suppression with the appropriate code, when invoked within a comment attached to a node that raises an error. To get this functionality in the on-demand mode of autocomplete we need to do some additional work, given that the existing context might not have the relevant error populated. To address this, when we are about to create an `Ac_comment` we also check the closest enclosing statement `stmt`, and run post-inference checks on `stmt`.

Changelog: [internal]

Reviewed By: SamChou19815

Differential Revision: D55053042

fbshipit-source-id: 3cad4a7423474f544c3faf2e3b232a338f985124

src/services/autocomplete/autocomplete_js.ml

@@ -151,6 +151,8 @@ class virtual ['T] process_request_searcher ~(from_trigger_character : bool) ~(c
     method virtual private infer_statement
         : (ALoc.t, 'T) Ast.Statement.t -> (ALoc.t, ALoc.t * Type.t) Ast.Statement.t
 
+    method virtual private check_closest_enclosing_statement : unit
+
     method virtual private type_of_component_name_of_jsx_element
         : 'T -> (ALoc.t, 'T) Flow_ast.JSX.element -> Type.t
 
@@ -214,10 +216,11 @@ class virtual ['T] process_request_searcher ~(from_trigger_character : bool) ~(c
         result
 
     method! comment ((loc, Flow_ast.Comment.{ text; _ }) as c) =
-      if this#covers_target loc then
+      if this#covers_target loc then (
         let (token, word_loc) = extract_word cursor text in
+        this#check_closest_enclosing_statement;
         this#find (ALoc.of_loc word_loc) token (Ac_comment { text; loc })
-      else
+      ) else
         super#comment c
 
     method! t_identifier ((annot, { Flow_ast.Identifier.name; _ }) as ident) =
@@ -945,6 +948,9 @@ class typed_ast_process_request_searcher ~(from_trigger_character : bool) ~(curs
       | _ ->
         (* impossible thanks to calling context of type_of_class_id *)
         Type.(AnyT.at Untyped loc)
+
+    (* This is a no-op since we have already checked the entire AST. *)
+    method private check_closest_enclosing_statement = ()
   end
 
 module Statement = Fix_statement.Statement_
@@ -981,6 +987,42 @@ class on_demand_process_request_searcher cx ~(from_trigger_character : bool) ~(c
 
     method private infer_statement stmt = Statement.statement cx stmt
 
+    method private check_closest_enclosing_statement =
+      let last_stmt = ref None in
+      Base.List.iter
+        ~f:(function
+          | Typed_ast_finder.EnclosingStatement stmt -> last_stmt := Some stmt
+          | _ -> ())
+        enclosing_node_stack;
+      Base.Option.iter !last_stmt ~f:(fun ((loc, _) as s) ->
+          (* Check the closest statement *)
+          let s' = Statement.statement cx s in
+          let ast =
+            ( loc,
+              {
+                Ast.Program.statements = [s];
+                interpreter = None;
+                comments = None;
+                all_comments = [];
+              }
+            )
+          in
+          let tast =
+            ( loc,
+              {
+                Ast.Program.statements = [s'];
+                interpreter = None;
+                comments = None;
+                all_comments = [];
+              }
+            )
+          in
+          let metadata = Context.metadata cx in
+          (* We need to also run post-inference checks since some errors are
+           * raised there. *)
+          Merge_js.post_merge_checks cx ast tast metadata
+      )
+
     method private type_of_class_id loc cls =
       let open Ast.Statement in
       match this#infer_statement (loc, ClassDeclaration cls) with

src/services/autocomplete/autocomplete_js.mli

@@ -99,6 +99,8 @@ class virtual ['T] process_request_searcher :
        method virtual private infer_statement :
          (ALoc.t, 'T) Flow_ast.Statement.t -> (ALoc.t, ALoc.t * Type.t) Flow_ast.Statement.t
 
+       method virtual private check_closest_enclosing_statement : unit
+
        method virtual private type_of_component_name_of_jsx_element :
          'T -> (ALoc.t, 'T) Flow_ast.JSX.element -> Type.t