A lot of the helpers in `helpers.ts` are heavily bound to NodeJS and at
the moment we're trying to make the `Connection` class be able to run in
multiple environments. Its only remaining Node dependency was its
reliance on `helpers.ts`, which it only needed for `assert`.
This is a useful change also because `helpers.ts` is quite large and
full of functions that do different things; I think we can name them
better and move them into modules with a specific purpose rather than a
generic `"helpers"` dumping ground.
Once this change lands `Connection` should be usable in the browser.
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.
Node's promisify function and the TS types for it give much better type understanding when wrapping a function in `promisify`. This change means we don't maintain our own implementation and our own (sub-par) types and rather lean on the tested and thorough @types/node version instead.
* chore: migrate src/ExecutionContext to TypeScript
I spent a while trying to decide on the best course of action for
typing the `evaluate` function.
Ideally I wanted to use generics so that as a user you could type
something like:
```
handle.evaluate<HTMLElement, number, boolean>((node, x) => true, 5)
```
And have TypeScript know the arguments of `node` and `x` based on those
generics. But I hit two problems with that:
* you have to have n overloads of `evaluate` to cope for as many number
of arguments as you can be bothered too (e.g. we'd need an overload for
1 arg, 2 args, 3 args, etc)
* I decided it's actually confusing because you don't know as a user
what those generics actually map to.
So in the end I went with one generic which is the return type of the
function:
```
handle.evaluate<boolean>((node, x) => true, 5)
```
And `node` and `x` get typed as `any` which means you can tell TS
yourself:
```
handle.evaluate<boolean>((node: HTMLElement, x: number) => true, 5)
```
I'd like to find a way to force that the arguments after the function do
match the arguments you've given (in the above example, TS would moan if
I swapped that `5` for `"foo"`), but I tried a few things and to be
honest the complexity of the types wasn't worth it, I don't think.
I'm very open to tweaking these but I'd rather ship this and tweak going
forwards rather than spend hours now tweaking. Once we ship these
typedefs and get feedback from the community I'm sure we can improve
them.
The codebase was incredibly inconsistent with the use of spacing around
curly braces, e.g.:
```
// this?
const a = {b: 1}
// or?
const a = { b: 1 }
```
This extended into import statements also. Google's styleguide is no
spacing, so we're going with that.
* 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
* chore: migrate `src/pipetransport` to typescript
Hit one bump in the fact that I want to share an interface across files.
TypeScript only lets you import/export these if you're using ESM, not
CommonJS. So the two options are:
- Migrate to ESM on a per file basis as we do this migration. This won't
affect the output as we output as CommonJS.
- Create a global `types.d.ts` file that we'll use and then migrate to
ESM after.
Right now I've gone for the second option in order to not introduce more
changes in one go. But if we end up finding we have lots of
interfaces/types/etc that we want modules to expose, we might decide
slowly introducing ESM might be a better way forwards.
* Update src/types.d.ts
Co-Authored-By: Mathias Bynens <mathias@qiwi.be>
This PR migrates the helper module to TypeScript. It's a bit of a bigger
change than others because I decided to move away from the helper class
with static methods and move towards a simpler set up where the module
is a bunch of functions. I still expose them under the `helper`
namespace to avoid this being a big change - we can update that later
when we migrate to ESM.
We do have to do some unfortunate wrangling of the promisify function.
Ideally I'd like to rely on the Node one (and the type defs) but that
doesn't work in Browserify land. I've stuck with the promisify in
`helper.ts` but pulled it into its own module to enable me to leave a
comment clarifying why we use it and the context. We can solve this with
a better web bundling story but that work is lower priority right now
than getting the `src/` directory into TypeScript.
