Infinity returns null when serialized

From RFC4627:

  Numeric values that cannot be represented as sequences of digits (such
  as Infinity and NaN) are not permitted.

NaN is invalid, so we already return null.

spec/driver_spec.rb

@@ -408,6 +408,11 @@ describe Capybara::Webkit::Driver do
       result.should == nil
     end
 
+    it "evaluates Infinity and returns null" do
+      result = driver.evaluate_script(%<Infinity>)
+      result.should == nil
+    end
+
     it "evaluates Javascript and returns an object" do
       result = driver.evaluate_script(%<({ 'one' : 1 })>)
       result.should == { 'one' => 1 }

src/JsonSerializer.cpp

@@ -1,4 +1,5 @@
 #include "JsonSerializer.h"
+#include <cmath>
 
 JsonSerializer::JsonSerializer(QObject *parent) : QObject(parent) {
 }
@@ -24,7 +25,10 @@ void JsonSerializer::addVariant(const QVariant &object) {
         }
         break;
       case QMetaType::Double:
-        m_buffer.append(object.toString());
+        if (std::isinf(object.toDouble()))
+          m_buffer.append("null");
+        else
+          m_buffer.append(object.toString());
         break;
       case QMetaType::QVariantMap:
         {