🐛 ✨Fix eval setCurrentStory error + make logging better

[nilshah98]

Description-

• Fixed logging, earler we were just doing reject() without passing any error, hence it was passed as undefined and hence error was undefined and we were unable to parse message from it
• Fixed issue where loading iframe.html as base preview URL would trigger the storyMissing event which would call reject and break flow. Solution for this was to open first component, instead of /iframe.html

[ninadbstack]

Do we get original error passed to us, if yes we can wrap and rethrow it

[nilshah98]

Even tried -

      channel.on('storyMissing', (err) => {
        reject(err);
      });

But this again resulted in -
[percy] TypeError: Cannot read properties of undefined (reading 'message')

[nilshah98]

Oh, just learned something new about JS which explains this better.
Whenever a function name is passed as callback, it calls the function by whatever parameters are passed.
So, in this case

channel.on('storyMissing', reject)

This would call reject with whatever parameters are passed to eventListener, and since nothing is passed, hence we reject with undefined resulting in above error.

[ninadbstack]

so basically story missing isnt passing anything ...
Also its not a new thing, its a standard thing that works across almost all languages ( except where brackets are not required for a function call, Ruby 👀 ), it works because its no different, it expects a function and you are passing a function

[nilshah98]

so basically story missing isnt passing anything ...

yes

Also its not a new thing, its a standard thing that works across almost all languages ( except where brackets are not required for a function call, Ruby 👀 ), it works because its no different, it expects a function and you are passing a function

Wasn't aware of this, thanks!

[ninadbstack]

Word change ? Is this same for v6 and v7

[nilshah98]

This is a custom error that we are throwing.
Earlier in the test itself, we were mocking the error to be thrown, since storyErrored event was caught, but we reject the promise and passed nothing to it, so it returned undefined and fell back to the mocked error.

Okay, now I understand this a little better.
Earlier we were calling c (callback) with new Error('Story Error')

channel.on('storyErrored'. reject)

This would result in reject being called with the new Error('Story Error'), but since we have seen circumstances where nothing is passed to the callback which results in rejection with undefined, and hence added a custom message of Story Errored, instead of relying on default arguments.

Edit: Updated the mock to execute callback with no arguments, instead of new Error('Story Error')

[nilshah98]

Refactored error throwing logic, so as to not update tests.

[ninadbstack]

LGTM