raise error when parsing object with NaN or INF to JSON

Summary:
NaN or INF is not allowed according to JSON specification.
This will cause problems when other places try to encode the output
of toJson with NaN or INF.
raise error when parsing object with NaN or INF to JSON.

Test Plan: manually test, raise error for object w/ NaN

Reviewed By: delong.j@fb.com

FB internal diff: D1143853

folly/json.cpp

@@ -126,6 +126,11 @@ struct Printer {
   void operator()(dynamic const& v) const {
     switch (v.type()) {
     case dynamic::DOUBLE:
+      if (!opts_.allow_nan_inf &&
+          (isnan(v.asDouble()) || isinf(v.asDouble()))) {
+        throw std::runtime_error("folly::toJson: JSON object value was a "
+          "NaN or INF");
+      }
       toAppend(v.asDouble(), &out_);
       break;
     case dynamic::INT64: {
@@ -751,6 +756,7 @@ fbstring toPrettyJson(dynamic const& dyn) {
 void dynamic::print_as_pseudo_json(std::ostream& out) const {
   json::serialization_opts opts;
   opts.allow_non_string_keys = true;
+  opts.allow_nan_inf = true;
   out << json::serialize(*this, opts);
 }
 

folly/json.h

@@ -61,6 +61,7 @@ namespace json {
       , allow_trailing_comma(false)
       , sort_keys(false)
       , skip_invalid_utf8(false)
+      , allow_nan_inf(false)
     {}
 
     // If true, keys in an object can be non-strings.  (In strict
@@ -93,6 +94,9 @@ namespace json {
 
     // Replace invalid utf8 characters with U+FFFD and continue
     bool skip_invalid_utf8;
+
+    // true to allow NaN or INF values
+    bool allow_nan_inf;
   };
 
   /*