Vendoring Puppeteer
===================

As mentioned in the chapter on [Testing], we run the full [Puppeteer
test suite] on try.  These tests are vendored in central under
_remote/test/puppeteer/_ and we have a script to pull in upstream changes.

We periodically perform a manual two-way sync. Below is an outline of the
process interspersed with some tips.

1. Clone the Puppeteer git repository and checkout the release tag you want
   to vendor into mozilla-central.

    	% git checkout tags/v10.0 -b sync-v10.0

2. Apply any recent changes in `remote/test/puppeteer` to the Puppeteer branch
   created above.

	 You might want to [install the project] at this point and make sure unit
	 tests pass. Check the project's `package.json` for relevant testing commands.

   You should use this as basis for a PR to the Puppeteer project once you are
	 satisfied that the two-way sync will be successful in mozilla-central. See
	 their [CONTRIBUTING.md].

	 Typically, the changes we push to Puppeteer include unskipping newly passing
	 unit tests for Firefox along with minor fixes to the tests or
	 to Firefox-specific browser-fetching and launch code.

	 Be sure to [run tests against both Chromium and Firefox] in the Puppeteer
	 repo. You can specify your local Firefox build when you do so:

		% BINARY=<path-to-objdir-binary> npm run funit

3. Now back in mozilla-central, you can run the following mach command to
	 copy over the Puppeteer branch you just prepared. The mach command has
	 flags to specify a local or remote repository as well as a commit.

		% ./mach remote vendor-puppeteer

	 By default, this command also installs the newly-pulled Puppeteer package
	 in order to generate a new `package-lock.json` file for the purpose of
	 pinning Puppeteer dependencies for our CI. There is a `--no-install` option
	 if you want to skip this step; for example, if you want to run installation
	 separately at a later point.

4. Go through the changes under `remote/test/puppeteer/test` and [unskip] any
	 newly-skipped tests (e.g. change `itFailsFirefox` to `it`).
	 A mass-change with `awk` might be useful here.

	 Why do we do this? The Puppeteer team runs their unit tests against Firefox
	 in their CI with many tests skipped. In contrast, we leave these tests
	 unskipped in Mozilla CI and track test expectation metadata
	 in [puppeteer-expected.json] instead.

5. Use `./mach puppeteer-test` (see [Testing]) to run Puppeteer tests against
   both Chromium and Firefox in headless mode. Again, only running a subset of
	 tests against Firefox is fine -- at this point you just want to check that
	 the typescript compiles and the browser binaries are launched successfully.

6. Next you want to update the test expectation metadata: test results might
   have changed, tests may have been renamed, removed or added. The
	 easiest way to do this is to run the Puppeteer test job on try
	 (see [Testing]). You will find the new test metadata as an artifact on that
	 job and you can copy it over into your sync patch if it looks reasonable.

	 Examine the job logs and makes sure the run didn't get interrupted early
	 by a crash or a hang, especially if you see a lot of
	 `TEST-UNEXPECTED-MISSING` in the Treeherder Failure Summary. You might need
	 to add new test skips or fix some new bug in the unit tests. This is the
	 fun part.

7. Once you are happy with the metadata and are ready to submit the sync patch
   up for review, run the Puppeteer test job on try again with `--rebuild 10`
	 to check for stability.

[Testing]: ./Testing.html
[Puppeteer test suite]: https://github.com/GoogleChrome/puppeteer/tree/master/test
[re-install the project]: https://github.com/puppeteer/puppeteer/blob/main/CONTRIBUTING.md#getting-code
[run tests against both Chromium and Firefox]: https://github.com/puppeteer/puppeteer/blob/main/test/README.md#running-tests
[puppeteer-expected.json]: https://searchfox.org/mozilla-central/source/remote/puppeteer-expected.json
[CONTRIBUTING.md]: https://github.com/puppeteer/puppeteer/blob/main/CONTRIBUTING.md
[unskip]: https://github.com/puppeteer/puppeteer/blob/main/test/README.md#skipping-tests-in-specific-conditions