Band-aid for preventMunge in cycle

Summary:
When the leader of a cycle has preventMunge then munged properties in other members of the are erroneously checked by assert_ground.

This diff is a band-aid to fix that problem by explicitly passing `should_munge_underscores` from the cycle members directly to `assert_ground`.

Any other file-specific configurations will suffer from this same problem in all merge step phases. The more principled long-term solution is to set up the types of the contexts so that you cannot access file specific information during merge.

Reviewed By: gabelevi

Differential Revision: D17398933

fbshipit-source-id: 6aca1054684cdbadced0273232002c7f30991508

src/typing/assert_ground.ml

@@ -38,7 +38,7 @@ class type_finder t =
 module Kit (Flow : Flow_common.S) : Flow_common.ASSERT_GROUND = struct
   include Flow
 
-  class assert_ground_visitor r ~max_reasons =
+  class assert_ground_visitor r ~max_reasons ~should_munge_underscores =
     object (self)
       inherit [Marked.t] Type_visitor.t as super
 
@@ -289,7 +289,7 @@ module Kit (Flow : Flow_common.S) : Flow_common.ASSERT_GROUND = struct
         let props = Context.find_props cx id in
         SMap.fold
           (fun x p acc ->
-            if is_munged_prop_name cx x then
+            if is_munged_prop_name_with_munge x ~should_munge_underscores then
               acc
             else if SSet.mem x init then
               Property.read_t p |> Option.fold ~f:(self#type_ cx pole) ~init:acc
@@ -357,9 +357,12 @@ module Kit (Flow : Flow_common.S) : Flow_common.ASSERT_GROUND = struct
             seen
     end
 
-  let enforce_strict cx t =
+  let enforce_strict cx t ~should_munge_underscores =
     let visitor =
-      new assert_ground_visitor (reason_of_t t) ~max_reasons:(Context.max_trace_depth cx)
+      new assert_ground_visitor
+        (reason_of_t t)
+        ~max_reasons:(Context.max_trace_depth cx)
+        ~should_munge_underscores
     in
     let seen = visitor#type_ cx Polarity.Positive Marked.empty t in
     ignore (seen : Marked.t)

src/typing/flow_common.ml

@@ -11,7 +11,7 @@ open Type
 (* This is here instead of assert_ground.ml to avoid the duplication of the enforce strict
  * signature *)
 module type ASSERT_GROUND = sig
-  val enforce_strict : Context.t -> Type.t -> unit
+  val enforce_strict : Context.t -> Type.t -> should_munge_underscores:bool -> unit
 end
 
 module type TRUST_CHECKING = sig
@@ -64,6 +64,8 @@ module type S = sig
 
   val is_munged_prop_name : Context.t -> name -> bool
 
+  val is_munged_prop_name_with_munge : name -> should_munge_underscores:bool -> bool
+
   val lookup_builtin :
     Context.t -> ?trace:Trace.t -> string -> reason -> Type.lookup_kind -> Type.t -> unit
 

src/typing/flow_js.ml

@@ -9027,7 +9027,12 @@ struct
  * the `munge_underscores` config option is set.
  *)
   and is_munged_prop_name cx name =
-    Context.should_munge_underscores cx && Signature_utils.is_munged_property_name name
+    is_munged_prop_name_with_munge
+      name
+      ~should_munge_underscores:(Context.should_munge_underscores cx)
+
+  and is_munged_prop_name_with_munge name ~should_munge_underscores =
+    Signature_utils.is_munged_property_name name && should_munge_underscores
 
   and lookup_prop cx trace l reason_prop reason_op strict x action =
     let l =

src/typing/flow_js.mli

@@ -113,7 +113,7 @@ val mk_typeof_annotation :
 (* strict *)
 val types_of : Constraint.constraints -> Type.t list
 
-val enforce_strict : Context.t -> Type.t -> unit
+val enforce_strict : Context.t -> Type.t -> should_munge_underscores:bool -> unit
 
 val possible_types : Context.t -> Constraint.ident -> Type.t list
 

src/typing/merge_js.ml

@@ -197,7 +197,10 @@ let detect_invalid_type_assert_calls cx file_sigs cxs tasts =
 let force_annotations leader_cx other_cxs =
   Core_list.iter
     ~f:(fun cx ->
-      Context.module_ref cx |> Flow_js.lookup_module leader_cx |> Flow_js.enforce_strict leader_cx)
+      let should_munge_underscores = Context.should_munge_underscores cx in
+      Context.module_ref cx
+      |> Flow_js.lookup_module leader_cx
+      |> Flow_js.enforce_strict leader_cx ~should_munge_underscores)
     (leader_cx :: other_cxs)
 
 let is_builtin_or_flowlib cx =

tests/munge_underscores_assert_ground_cycle/.flowconfig

@@ -0,0 +1,2 @@
+[options]
+munge_underscores=true

tests/munge_underscores_assert_ground_cycle/a.js

@@ -0,0 +1,4 @@
+//@flow
+//@preventMunge
+const b = require('./b');
+module.exports = b.x;

tests/munge_underscores_assert_ground_cycle/b.js

@@ -0,0 +1,8 @@
+//@flow
+const a = require('./a');
+class A {
+  static x: number = 3;
+  _munged(arg) { return a; }
+}
+
+module.exports = A;

tests/munge_underscores_assert_ground_cycle/munge_underscores_assert_ground_cycle.exp

@@ -0,0 +1 @@
+Found 0 errors