Sugar for exact object types

Summary: Adds support for `{| ... |}` exact object type declaration syntax. Given an object type `{ a: X, b: Y, ... }`, `{| a: X, b: Y, ... |}` is synonymous with `$Exact<{ a: X, b: Y, ... }>`. Note that `$Exact<X>` is still the only way to express the exact version of an aliased object type `X`. Reviewed By: avikchaudhuri Differential Revision: D3714440 fbshipit-source-id: df4ffa43a35397445880f6315c42b44edf60a527
facebook · Aug 17, 2016 · c710c40 · c710c40
1 parent b11bbbc
commit c710c40
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Showing 10 changed files with 70 additions and 36 deletions.
diff --git a/newtests/exact/prop_test2.js b/newtests/exact/prop_test2.js
@@ -1,36 +1,29 @@
 /***
- * more prop tests on unions of objects.
- * to see why property existence tests don't work to refine inexact types,
- * take a look at checkFlag_err() below.
+ * more prop tests on unions of objects,
+ * using {| ... |} annotation syntax
  */
 
-type StringFlag = {
+type Flag = {|
   type: "string",
   name: string,
   description: string,
   argName: string,
   aliases?: Array<string>,
   default?: string,
-};
-
-type BoolFlag = {
+|} | {|
   type: "boolean",
   name: string,
   description: string,
   aliases?: Array<string>,
-};
-
-type EnumFlag = {
+|} | {|
   type: "enum",
   name: string,
   description: string,
   argName: string,
   validValues: Array<string>,
   aliases?: Array<string>,
   default?: string,
-};
-
-type Flag = $Exact<StringFlag> | $Exact<BoolFlag> | $Exact<EnumFlag>;
+|};
 
 function checkFlag_ok(flag: Flag): string {
   if (flag.default) {

diff --git a/src/parser/estree_translator.ml b/src/parser/estree_translator.ml
@@ -940,6 +940,7 @@ end with type t = Impl.t) = struct
 
   and object_type (loc, o) = Type.Object.(
     node "ObjectTypeAnnotation" loc [|
+      "exact", bool o.exact;
       "properties", array_of_list object_type_property o.properties;
       "indexers", array_of_list object_type_indexer o.indexers;
       "callProperties", array_of_list object_type_call_property o.callProperties;

diff --git a/src/parser/lexer_flow.mll b/src/parser/lexer_flow.mll
@@ -21,6 +21,8 @@ module Token = struct
     (* Syntax *)
     | T_LCURLY
     | T_RCURLY
+    | T_LCURLYBAR
+    | T_RCURLYBAR
     | T_LPAREN
     | T_RPAREN
     | T_LBRACKET
@@ -211,6 +213,8 @@ module Token = struct
     | T_AWAIT -> "T_AWAIT"
     | T_LCURLY -> "T_LCURLY"
     | T_RCURLY -> "T_RCURLY"
+    | T_LCURLYBAR -> "T_LCURLYBAR"
+    | T_RCURLYBAR -> "T_RCURLYBAR"
     | T_LPAREN -> "T_LPAREN"
     | T_RPAREN -> "T_RPAREN"
     | T_LBRACKET -> "T_LBRACKET"
@@ -1091,6 +1095,8 @@ and type_token env = parse
   | "]"                { env, T_RBRACKET }
   | "{"                { env, T_LCURLY }
   | "}"                { env, T_RCURLY }
+  | "{|"               { env, T_LCURLYBAR }
+  | "|}"               { env, T_RCURLYBAR }
   | "("                { env, T_LPAREN }
   | ")"                { env, T_RPAREN }
   | "..."              { env, T_ELLIPSIS }

diff --git a/src/parser/parser_flow.ml b/src/parser/parser_flow.ml
@@ -201,9 +201,10 @@ end = struct
           loc, Type.Exists
       | T_LESS_THAN -> _function env
       | T_LPAREN -> function_or_group env
-      | T_LCURLY ->
-          let loc, o = _object env in
-          loc, Type.Object o
+      | T_LCURLY
+      | T_LCURLYBAR ->
+        let loc, o = _object env ~allow_exact:true in
+        loc, Type.Object o
       | T_TYPEOF ->
           let start_loc = Peek.loc env in
           Expect.token env T_TYPEOF;
@@ -465,27 +466,35 @@ end = struct
           static;
         })
 
-      in let semicolon env =
+      in let semicolon exact env =
         match Peek.token env with
         | T_COMMA | T_SEMICOLON -> Eat.token env
-        | T_RCURLY -> ()
+        | T_RCURLYBAR when exact -> ()
+        | T_RCURLY when not exact -> ()
         | _ -> error_unexpected env
 
-      in let rec properties ~allow_static env (acc, indexers, callProperties) =
+      in let rec properties ~allow_static ~exact env
+        (acc, indexers, callProperties) =
         let start_loc = Peek.loc env in
         let static = allow_static && Expect.maybe env T_STATIC in
         match Peek.token env with
-        | T_EOF
-        | T_RCURLY -> List.rev acc, List.rev indexers, List.rev callProperties
+        | T_EOF ->
+          List.rev acc, List.rev indexers, List.rev callProperties
+        | T_RCURLYBAR when exact ->
+          List.rev acc, List.rev indexers, List.rev callProperties
+        | T_RCURLY when not exact ->
+          List.rev acc, List.rev indexers, List.rev callProperties
         | T_LBRACKET ->
           let indexer = indexer_property env start_loc static in
-          semicolon env;
-          properties allow_static env (acc, indexer::indexers, callProperties)
+          semicolon exact env;
+          properties allow_static exact env
+            (acc, indexer::indexers, callProperties)
         | T_LESS_THAN
         | T_LPAREN ->
           let call_prop = call_property env start_loc static in
-          semicolon env;
-          properties allow_static env (acc, indexers, call_prop::callProperties)
+          semicolon exact env;
+          properties allow_static exact env
+            (acc, indexers, call_prop::callProperties)
         | _ ->
           let static, (_, key) = match static, Peek.token env with
           | true, T_COLON ->
@@ -507,17 +516,20 @@ end = struct
           | T_LESS_THAN
           | T_LPAREN -> method_property env start_loc static key
           | _ -> property env start_loc static key in
-          semicolon env;
-          properties allow_static env (property::acc, indexers, callProperties)
+          semicolon exact env;
+          properties allow_static exact env
+            (property::acc, indexers, callProperties)
 
-      in fun ?(allow_static=false) env ->
+      in fun ?(allow_static=false) ?(allow_exact=false) env ->
+        let exact = allow_exact && Peek.token env = T_LCURLYBAR in
         let start_loc = Peek.loc env in
-        Expect.token env T_LCURLY;
+        Expect.token env (if exact then T_LCURLYBAR else T_LCURLY);
         let properties, indexers, callProperties =
-          properties ~allow_static env ([], [], []) in
+          properties ~allow_static ~exact env ([], [], []) in
         let end_loc = Peek.loc env in
-        Expect.token env T_RCURLY;
+        Expect.token env (if exact then T_RCURLYBAR else T_RCURLY);
         Loc.btwn start_loc end_loc, Type.Object.({
+          exact;
           properties;
           indexers;
           callProperties
@@ -644,7 +656,8 @@ end = struct
     let type_parameter_declaration =
       wrap (type_parameter_declaration ~allow_default:false)
     let type_parameter_instantiation = wrap type_parameter_instantiation
-    let _object ?(allow_static=false) env = wrap (_object ~allow_static) env
+    let _object ?(allow_static=false) env =
+      wrap (_object ~allow_static ~allow_exact:false) env
     let function_param_list = wrap function_param_list
     let annotation = wrap annotation
     let annotation_opt = wrap annotation_opt

diff --git a/src/parser/spider_monkey_ast.ml b/src/parser/spider_monkey_ast.ml
@@ -90,6 +90,7 @@ and Type : sig
       }
     end
     type t = {
+      exact: bool;
       properties: Property.t list;
       indexers: Indexer.t list;
       callProperties: CallProperty.t list;

diff --git a/src/parser/test/custom_ast_types.js b/src/parser/test/custom_ast_types.js
@@ -66,3 +66,6 @@ def("DeclareFunction")
 
 def("Function")
     .field("predicate", or(def("Predicate"), null), defaults["null"])
+
+def("ObjectTypeAnnotation")
+    .field("exact", Boolean)
diff --git a/src/parser/test/esprima_test_runner.js b/src/parser/test/esprima_test_runner.js
@@ -217,6 +217,9 @@ function handleSpecialObjectCompare(esprima, flow, env) {
         esprima.typeAnnotation = null;
       }
       break;
+    case 'ObjectTypeAnnotation':
+      esprima.exact = esprima.exact || false;
+      break;
     case 'ObjectTypeProperty':
     case 'ObjectTypeIndexer':
     case 'ObjectTypeCallProperty':

diff --git a/src/parser/test/hardcoded_tests.js b/src/parser/test/hardcoded_tests.js
@@ -177,7 +177,7 @@ module.exports = {
                   'key.name': 'numVal',
                   'value.type': 'NumberTypeAnnotation',
                 }
-              ]
+              ],
             }
           }
         }
@@ -826,6 +826,20 @@ module.exports = {
         }
       }
     },
+    'Exact object types': {
+      'var obj: {| x: number, y: string |}': {  // no trailing comma
+        'body.0.declarations.0.id.typeAnnotation.typeAnnotation': {
+          'type': 'ObjectTypeAnnotation',
+          'exact': true,
+        },
+      },
+      'var obj: {| x: number, y: string, |}': {  // trailing comma
+        'body.0.declarations.0.id.typeAnnotation.typeAnnotation': {
+          'type': 'ObjectTypeAnnotation',
+          'exact': true,
+        },
+      }
+    },
     'Tuples': {
       'var a : [] = [];': {
         'body.0.declarations.0.id.typeAnnotation.typeAnnotation': {

diff --git a/src/typing/class_sig.ml b/src/typing/class_sig.ml
@@ -559,7 +559,7 @@ let extract_mixins _cx =
 let mk_interface cx loc reason structural self = Ast.Statement.(
   fun { Interface.
     typeParameters;
-    body = (_, { Ast.Type.Object.properties; indexers; callProperties });
+    body = (_, { Ast.Type.Object.properties; indexers; callProperties; _ });
     extends;
     mixins;
     _;

diff --git a/src/typing/type_annotation.ml b/src/typing/type_annotation.ml
@@ -444,7 +444,7 @@ let rec convert cx tparams_map = Ast.Type.(function
   in
   if (tparams = []) then ft else PolyT(tparams, ft)
 
-| loc, Object { Object.properties; indexers; callProperties; } ->
+| loc, Object { Object.exact; properties; indexers; callProperties; } ->
   let props_map = List.fold_left (
     fun props_map (loc, { Object.Property.key; value; optional; _ }) ->
       (match key with
@@ -513,7 +513,7 @@ let rec convert cx tparams_map = Ast.Type.(function
   let proto = MixedT (reason_of_string reason_desc, Mixed_everything) in
   let flags = {
     sealed = if sealed then Sealed else UnsealedInFile (Loc.source loc);
-    exact = not sealed;
+    exact = not sealed || exact;
     frozen = false;
   } in
   ObjT (mk_reason reason_desc loc,