fix(plugin-inline-script-content): Ensure event handlers added before Bugsnag can be removed

[bengourley]

Fixes a bug where an event handler added before Bugsnag is initialised cannot be removed.

The following snippet will continue to log clicks after the removeEventListener function is called:

function click (e) {
  console.log('click event', e)
}
window.addEventListener('click', logClick)
var bugsnagClient = bugsnag('API_KEY')
window.removeEventListener('click', logClick)

With this fix it is now removed correctly.

Details

The inline script tracking code wraps addEventListener() callbacks in a function that tracks where it came from. Since removeEventListener() takes a reference to the function that should be removed, passing it the wrapped function means it is not the same reference as the original function that was added.

The solution is to do as Bugsnag v3 did and call removeEventListener() with both the wrapped and un-wrapped function.

Aside

In debugging this, I also noticed addEventListener() was being wrapped multiple times. It turned out that this is because all of the entries in the list of event target classes share the same object prototype upon which the original addEventListener() is defined. The check is updated to only wrap it if the object being inspected defines its own addEventListener function, rather than it being in the prototype chain.

[sazap10]

SFTM