Replacing the Node EventEmitter with Mitt caused more problems than
anticipated for end users due to the API differences and the amount of
people who relied on the EventEmitter API. In hindsight this clearly
should have been explored more and then released as a breaking v4.
This commit rolls us back to the built in Node EventEmitter library
which we can release to get everyone back on stable builds. We can then
consider our approach to migrating to Mitt and when we do do that we can
release it as a breaking change and properly document the migration
strategy and approach.
* chore: migrate to Mitt as the EventEmitter
This commit moves us to using Mitt [1] for the event emitter in
Puppeteer. This removes our dependency to Node's EventEmitter which is
part of a larger stream of work to enable a Puppeteer-web version that
doesn't depend on Node.
There are no large breaking changes as we support the main methods that
EventEmitter had, but it also provides some methods that Puppeteer
didn't use. Technically end users could depend on this but it's
unlikely.
[1]: https://github.com/developit/mitt
We should import them just like any other module. This commit makes that
change. It does not change any behaviours or the types themselves.
EXPECTED_PROTOCOL_DIFF as we're updating the structure of it.
* chore: remove src/externs.d.ts
It defined global types that we don't want to use, and instead we move
to using interfaces that we import and reference just like with any
other interface.
This means other than Protocol (which I think is fine to leave as is),
there are no other magic global types and you have to import any types
or interfaces that you want.
* chore: migrate src/helpers.ts to ESM
Doing this means we can avoid the global `types.d.ts` file and export
the interface via ESM instead.
I would ideally like to rewrite the helper module so that it doesn't
export all the functions under the `helper` namespace, but I'll leave
that for a separate PR to keep mechanical changes to one per PR and
easier to review.
* chore: migrate `src/Connection` to TypeScript
This commit migrates `src/Connection` to TypeScript. It also changes its
exports to be ESM because TypeScript's support for exporting values to
use as types via CommonJS is poor (by design) and so rather than battle
that it made more sense to migrate the file to ESM.
The good news is that TypeScript is still outputting to `lib/` as
CommonJS, so the fact that we author in ESM is actually not a breaking
change at all.
So going forwards we will:
* migrate TS files to use ESM for importing and exporting
* continue to output to `lib/` as CommonJS
* continue to use CommonJS requires when in a `src/*.js` file
I'd also like to split `Connection.ts` into two; I think the
`CDPSession` class belongs in its own file, but I will do that in
another PR to avoid this one becoming bigger than it already is.
I also turned off `@typescript-eslint/no-use-before-define` as I don't
think it was adding value and Puppeteer's codebase seems to have a style
of declaring helper functions at the bottom which is fine by me.
Finally, I updated the DocLint tool so it knows of expected method
mismatches. It was either that or come up with a smart way to support
TypeScript generics in DocLint and given we don't want to use DocLint
that much longer that didn't feel worth it.
* Fix params being required
