Add command hh --is-subtype <json

Summary:
This adds the `--is-subtype` command which allows you to pass JSON via stdin specifying type pairs. A list of results will be returned where each result indicates whether the first type is a subtype of the second type.

The first type can be either a position string (similar to `--type-at-pos`) or a json-representation of a type (same format that `--type-at-pos-batch` returns). e.g.

```
{"kind":"pos", "pos":"file:line:col"}
```
or

```
{"kind":"type", "type":TYPE_JSON}
```

The second type must be a json-representation of a type and must be a type that has an environment-independent definition (e.g. no type variables, this, etc).

While unbound names are checked for, some lack of type-wellformed-ness is not, e.g. arity of class types with generics.

The reason why two positions are not supported is because two positions may have different environments making subtyping a difficult question to answer. If a user is interested in the relationship b/t types at two positions, and one is known to not be environment-dependent, the user can use `--type-at-pos-batch` to get the JSON type of the independent one and then use that with `--is-subtype` and the other position.

Reviewed By: vassilmladenov

Differential Revision: D38393256

fbshipit-source-id: 55410eeec15845ed438a310b56cd69280cf5e217

Author: viratyosin

hphp/hack/src/client/clientArgs.ml

@@ -726,6 +726,9 @@ let parse_check_args cmd =
         Arg.String (fun x -> set_mode (MODE_TYPE_ERROR_AT_POS x)),
         " (mode) show type error at a given position in file [line:character]"
       );
+      ( "--is-subtype",
+        Arg.Unit (fun () -> set_mode MODE_IS_SUBTYPE),
+        " (mode) take a JSON list of subtype queries via stdin" );
       ( "--tast-holes",
         Arg.String (fun x -> set_mode (MODE_TAST_HOLES x)),
         " (mode) return all TAST Holes in a given file" );

hphp/hack/src/client/clientCheck.ml

@@ -512,6 +512,16 @@ let main (args : client_check_env) (local_config : ServerLocalConfig.t) :
       in
       List.iter responses ~f:print_endline;
       Lwt.return (Exit_status.No_error, telemetry)
+    | MODE_IS_SUBTYPE ->
+      let stdin = Sys_utils.read_stdin_to_string () in
+      let%lwt (response, telemetry) = rpc args @@ Rpc.IS_SUBTYPE stdin in
+      (match response with
+      | Ok str ->
+        Printf.printf "%s" str;
+        Lwt.return (Exit_status.No_error, telemetry)
+      | Error str ->
+        Printf.eprintf "%s" str;
+        raise Exit_status.(Exit_with Input_error))
     | MODE_TYPE_ERROR_AT_POS arg ->
       let tpos = Str.split (Str.regexp ":") arg in
       let (fn, line, char) =

hphp/hack/src/client/clientEnv.ml

@@ -73,6 +73,7 @@ type client_mode =
   | MODE_TYPE_AT_POS of string
   | MODE_TYPE_AT_POS_BATCH of string list
   | MODE_TYPE_ERROR_AT_POS of string
+  | MODE_IS_SUBTYPE
   | MODE_TAST_HOLES of string
   | MODE_FUN_DEPS_AT_POS_BATCH of string list
   | MODE_FILE_DEPENDENTS
@@ -174,6 +175,7 @@ let mode_to_string = function
   | MODE_TYPE_AT_POS _ -> "MODE_TYPE_AT_POS"
   | MODE_TYPE_AT_POS_BATCH _ -> "MODE_TYPE_AT_POS_BATCH"
   | MODE_TYPE_ERROR_AT_POS _ -> "MODE_TYPE_ERROR_AT_POS"
+  | MODE_IS_SUBTYPE -> "MODE_IS_SUBTYPE"
   | MODE_TAST_HOLES _ -> "MODE_TAST_HOLES"
   | MODE_FUN_DEPS_AT_POS_BATCH _ -> "MODE_FUN_DEPS_AT_POS_BATCH"
   | MODE_FILE_DEPENDENTS -> "MODE_FILE_LEVEL_DEPENDENCIES"

hphp/hack/src/server/dune

@@ -467,6 +467,7 @@
   serverIdle
   serverInferTypeBatch
   serverInvalidateUnits
+  serverIsSubtype
   serverLint
   serverMethodJumps
   serverMethodJumpsBatch

hphp/hack/src/server/serverCommand.ml

@@ -61,6 +61,7 @@ let rpc_command_needs_full_check : type a. a t -> bool =
   | INFER_TYPE _ -> false
   | INFER_TYPE_BATCH _ -> false
   | INFER_TYPE_ERROR _ -> false
+  | IS_SUBTYPE _ -> false
   | TAST_HOLES _ -> false
   | IDE_HOVER _ -> false
   | DOCBLOCK_AT _ -> false

hphp/hack/src/server/serverCommandTypes.ml

@@ -343,6 +343,7 @@ type _ t =
       (string * int * int * (int * int) option) list
       -> string list t
   | INFER_TYPE_ERROR : file_input * int * int -> InferErrorAtPosService.result t
+  | IS_SUBTYPE : string -> (string, string) result t
   | TAST_HOLES : file_input * Tast_hole.filter -> TastHolesService.result t
   | IDE_HOVER : string * int * int -> HoverService.result t
   | DOCBLOCK_AT :

hphp/hack/src/server/serverCommandTypesUtils.ml

@@ -7,6 +7,7 @@ let debug_describe_t : type a. a t -> string = function
   | INFER_TYPE _ -> "INFER_TYPE"
   | INFER_TYPE_BATCH _ -> "INFER_TYPE_BATCH"
   | INFER_TYPE_ERROR _ -> "INFER_TYPE_ERROR"
+  | IS_SUBTYPE _ -> "IS_SUBTYPE"
   | TAST_HOLES _ -> "TAST_HOLES"
   | IDE_HOVER _ -> "IDE_HOVER"
   | DOCBLOCK_AT _ -> "DOCBLOCK_AT"

hphp/hack/src/server/serverInferTypeBatch.ml

@@ -13,12 +13,10 @@ type pos = Relative_path.t * int * int * (int * int) option
 
 type spos = string * int * int * (int * int) option [@@deriving eq, ord]
 
-let recheck_typing ctx (pos_list : pos list) =
+let recheck_typing ctx (path_list : Relative_path.t list) =
   let files_to_check =
-    pos_list
-    |> List.map ~f:(fun (path, _, _, _) -> path)
+    List.sort path_list ~compare:Relative_path.compare
     |> List.remove_consecutive_duplicates ~equal:Relative_path.equal
-    (* note: our caller has already sorted pos_list *)
   in
   let (ctx, paths_and_tasts) =
     List.fold
@@ -33,6 +31,16 @@ let recheck_typing ctx (pos_list : pos list) =
   in
   (ctx, paths_and_tasts)
 
+let get_tast_map ctx path_list =
+  let (ctx, paths_and_tasts) = recheck_typing ctx path_list in
+  let tasts =
+    List.fold
+      paths_and_tasts
+      ~init:Relative_path.Map.empty
+      ~f:(fun map (key, data) -> Relative_path.Map.add map ~key ~data)
+  in
+  (ctx, tasts)
+
 let result_to_string result (fn, line, char, range_end) =
   Hh_json.(
     let obj =
@@ -57,13 +65,8 @@ let result_to_string result (fn, line, char, range_end) =
     json_to_string obj)
 
 let helper ctx acc pos_list =
-  let (ctx, paths_and_tasts) = recheck_typing ctx pos_list in
-  let tasts =
-    List.fold
-      paths_and_tasts
-      ~init:Relative_path.Map.empty
-      ~f:(fun map (key, data) -> Relative_path.Map.add map ~key ~data)
-  in
+  let path_list = List.map pos_list ~f:(fun (path, _, _, _) -> path) in
+  let (ctx, tasts) = get_tast_map ctx path_list in
   List.fold pos_list ~init:acc ~f:(fun acc pos ->
       let (fn, line, char, range_end) = pos in
       let result =

hphp/hack/src/server/serverInferTypeBatch.mli

@@ -6,6 +6,13 @@
  *
  *)
 
+type pos = Relative_path.t * int * int * (int * int) option
+
+val get_tast_map :
+  Provider_context.t ->
+  Relative_path.t list ->
+  Provider_context.t * Tast.program Relative_path.Map.t
+
 val go :
   MultiWorker.worker list option ->
   (string * int * int * (int * int) option) list ->