Include a stacktrace from JS engine

Author: andygeers

lib/react/renderer.rb

@@ -5,7 +5,8 @@ class Renderer
 
     class PrerenderError < RuntimeError
       def initialize(component_name, props, js_message)
-        message = "Encountered error \"#{js_message}\" when prerendering #{component_name} with #{props}"
+        message = ["Encountered error \"#{js_message}\" when prerendering #{component_name} with #{props}",
+                    js_message.backtrace.join("\n")].join("\n")
         super(message)
       end
     end

test/react_renderer_test.rb

@@ -32,7 +32,7 @@ class ReactRendererTest < ActiveSupport::TestCase
     end
     expected_message_one = 'Encountered error "ReferenceError: Can\'t find variable: NonexistentComponent" when prerendering NonexistentComponent with {"error":true,"exists":false}'
     expected_message_two = 'Encountered error "ReferenceError: NonexistentComponent is not defined" when prerendering NonexistentComponent with {"error":true,"exists":false}'
-    assert (expected_message_one == err.message || expected_message_two == err.message)
+    assert (err.message.starts_with?(expected_message_one) || err.message.starts_with?(expected_message_two))
   end
 
   test 'prerender errors are thrown when given a string' do
@@ -46,6 +46,6 @@ class ReactRendererTest < ActiveSupport::TestCase
     end
     expected_message_one = 'Encountered error "ReferenceError: Can\'t find variable: NonexistentComponent" when prerendering NonexistentComponent with {"error":true,"exists":false}'
     expected_message_two = 'Encountered error "ReferenceError: NonexistentComponent is not defined" when prerendering NonexistentComponent with {"error":true,"exists":false}'
-    assert (expected_message_one == err.message || expected_message_two == err.message)
+    assert (err.message.starts_with?(expected_message_one) || err.message.starts_with?(expected_message_two))
   end
 end