Fix optional catch binding

[styfle]

This fixes the scenario where the catch clause does not have a parameter defined.

For example:

try {
  console.log('foo')
} catch {
  console.log('bar')
}

This feature moved to stage 4 last year and is supported since Node 10 and Chrome 66.

[guybedford]

Happy to get this merged asap, thanks for the PR.

[guybedford]

Should this not be the empty array? Just seems like it would need a lot of guards for the params: undefined case, but if that is already handled then that is ok.

[styfle]

@guybedford I have no idea. This prevented the code from throwing TypeError: Cannot read property 'type' of null when I changed it.

I was following the example above for BlockStatement which does not assign params.

If you think an empty array is better, that seems to work too.

[lukastaegert]

By the current implementation, it does not really matter what you do, but again I would love to see a test to make sure this keeps working in the future.

[styfle]

@lukastaegert Thanks, I added a test 👍

[guybedford]

Can we make this null instead of undefined to match the ESTree approach then?

[styfle]

@guybedford It can't be null due to the interface:

interface ScopeOptions {
	parent?: AttachedScope;
	block?: boolean;
	params?: Array<Node>;
}

It can only be undefined or Array. I'll change it to [].

[lukastaegert]

Test would be nice

[styfle]

@lukastaegert I added a test but Windows CI is failing with the following:

ERR! Error: EPERM: operation not permitted, unlink 'C:\projects\rollup-pluginutils\node_modules\.staging\typescript-5413e3f3\lib\pl\diagnosticMessages.generated.json'

[styfle]

It looks like pushing again solved the CI issue ✅

[guybedford]

Released in 2.8.2.