[easy] Don't parse JSON files with strict mode

Summary:Strict mode does indeed address the octals difference between JS objects and JSON, but it also limits the ability to write duplicate properties in JSON (sometimes used as a way of writing comments in JSON).

While ES6 does permit duplicate object properties again, ES5 had the restriction -- so rather than removing the error from the parser entirely I figured we'd just stay conservative. I could be swayed here if someone feels strongly about this.

Reviewed By: gabelevi

Differential Revision: D3207718

fb-gh-sync-id: a1eb27979f3e6599f9a2ed5ffcff557db8b0198e
fbshipit-source-id: a1eb27979f3e6599f9a2ed5ffcff557db8b0198e

src/parsing/parsing_service_js.ml

@@ -88,7 +88,7 @@ let parse_json_file ~fail content file =
  esproposal_decorators = false;
  esproposal_export_star_as = false;
  types = true;
- use_strict = true; (* JSON bans octals; this only forbids legacy octals *)
+ use_strict = false;
  }) in
 
  (* parse the file as JSON, then munge the AST to convert from an object

tests/json/.flowconfig

@@ -0,0 +1,7 @@
+[ignore]
+
+[include]
+
+[libs]
+
+[options]

tests/json/json.exp

@@ -0,0 +1,2 @@
+
+Found 0 errors

tests/json/test.json

@@ -0,0 +1,4 @@
+{
+ "duplicates_are_allowed_in_json": 42,
+ "duplicates_are_allowed_in_json": 43
+}