Fix JSON::GeneratorError for objects with invalid UTF-8 in to_s (#1199)

Rollbar::Encoding.encode only processed String and Symbol types.
When objects with to_s methods returning invalid UTF-8 were included
in the payload, they bypassed encoding and caused JSON serialization
to fail with "source sequence is illegal/malformed utf-8".

Now all non-JSON-native types are passed through the Encoder, which
already calls to_s and handles encoding normalization.

Fixes #1196

Author: grk

lib/rollbar/encoding.rb

@@ -10,11 +10,12 @@ def self.setup
     end
 
     def self.encode(object)
-      can_be_encoded = object.is_a?(String) || object.is_a?(Symbol)
-
-      return object unless can_be_encoded
-
-      encoding_class.new(object).encode
+      case object
+      when Numeric, TrueClass, FalseClass, NilClass
+        object
+      else
+        encoding_class.new(object).encode
+      end
     end
   end
 end

spec/rollbar/util_spec.rb

@@ -134,10 +134,14 @@
     it 'should replace invalid utf8 values' do
       bad_key = force_to_ascii("inner \x92bad key")
 
+      class ObjClass; def to_s; "bad obj\255".force_encoding('ASCII-8BIT'); end; end
+      bad_obj = ObjClass.new
+
       payload = {
         :bad_value => force_to_ascii("bad value 1\255"),
         :bad_value2 => force_to_ascii("bad\255 value 2"),
         force_to_ascii("bad\255 key") => 'good value',
+        :bad_obj => bad_obj,
         :hash => {
           :inner_bad_value => force_to_ascii("\255\255bad value 3"),
           bad_key.to_sym => 'inner good value',
@@ -157,6 +161,7 @@
       payload_copy[:bad_value].should eq('bad value 1')
       payload_copy[:bad_value2].should eq('bad value 2')
       payload_copy['bad key'].should eq('good value')
+      payload_copy[:bad_obj].should eq('bad obj')
       payload_copy.keys.should_not include("bad\456 key")
       payload_copy[:hash][:inner_bad_value].should eq('bad value 3')
       payload_copy[:hash][:"inner bad key"].should eq('inner good value')