QCoreApplication::postEvent: Unexpected null receiver

[alexslade]

Getting this message popping up in 2 different cucumber test suits, not sure where it's coming from. Any ideas?

[jferris]

These are hard to track down. They happen when we try to send an event to an object we already deleted. In capybara-webkit, this is usually when a Command subclass receives an event after it's deleted. The best way I know of to track them down is to use print debugging to figure out what the socket dialog looks like that causes the error.

[fd]

Putting an if (m_command != NULL) around this line fixed the problem for me

[jferris]

Is there a good way to reproduce this? Can you write a test?

[fd]

Well a couple of days ago I first noticed the bug. So I did some digging and I didn't find out why m_command is NULL. But google pointed me in the direction of the NULL vs. deleteLater thing. Qt also has a ENV flag which shows some more debugging output: QT_FATAL_WARNINGS=1

[jferris]

Right; I need to know what actually causes this issue, though. Adding that if statement will only mask the symptom and not fix the problem, because it shouldn't be trying to delete a NULL command in the first place. I think the most likely culprit is that a command is emitting a response twice, which shouldn't happen.

[keithpitt]

This error pops up for me every once and a while. I'm trying to use #find_field at the time. I get this output in my cukes:

QCoreApplication::postEvent: Unexpected null receiver

And it fails with the following error:

Unknown command: f::select][not(./@type = 'submit' or ./@type = 'image' or ./@type = 'hidden')][((./@id = 'Product Group' or ./@name = 'Product
 (Capybara::Driver::Webkit::WebkitError)
./features/step_definitions/input_steps.rb:3:in `/^the "([^"]*)" drop-down should contain the option "([^"]*)"$/'
features/product_groups.feature:19:in `Then the "Product Group" drop-down should contain the option "Shoes"'

My step that produces the error, looks like this:

Then /^the "([^"]*)" drop-down should contain the option "([^"]*)"$/ do |label, selected_options|
  field = find_field(label)
  options = all(%{##{field[:id]} option[selected]}).map { |a| a.text }
  options.join(', ').should == selected_options
end

It blows up on the field = find_field(label) line. I hope this helps...

[jferris]

I found a couple possible paths that led to this error and fixed them. Can you guys try again with 0.3.0?

[jferris]

I'm going to assume this is fixed unless somebody else runs into it.

[cmeiklejohn]

I was experiencing this but as of 0.4.1 I'm not anymore.

[alexslade]

Still getting the error with 0.5.0
What's worse, it seems to be a bit sporadic, one example scenario will pass 30% of the time.

cannot select option, no option with text 'Call To Action' in select box 'Select the type of component' (Capybara::ElementNotFound)

(A couple of steps after the 'QCoreApplication::postEvent: Unexpected null receiver' gets printed. If the postEvent error doesn't happen, the feature passes)

What debug info would be most useful here to work out what's going on?

[ignu]

This is happening for me on the 1.0 branch when I try to run any javascript.

[cmeiklejohn]

I'm still getting this. Just experienced it on 0.4.0.

[mikepack]

Still an issue for me. I noticed that when I do run into this problem, it happens on almost all tests in the suite. When it doesn't occur, it happens on none of them. It's also quite sporadic and unpredictable, occurring sometimes on a test that has previously passed and is unchanged.

Sometimes I receive this corresponding error:
INVALID_EXPRESSION_ERR: DOM XPath Exception 51: The expression had a syntax error or otherwise is not a legal expression according to the rules of the specific XPathEvaluator.

[keithpitt]

Just out of interest, can you run your HTML through some sort of validator?