This disables symbol renaming in production builds. The original
variable and function names are preserved. All other forms of
compression applied by Closure (dead code elimination, inlining, etc)
are unchanged — the final program is identical to what we were producing
before, just in a more readable form.
The motivation is to make it easier to debug React issues that only
occur in production — the same reason we decided to start shipping
sourcemaps in #28827 and #28827.
However, because most apps run their own minification step on their npm
dependencies, it's not necessary for us to minify the symbols before
publishing — it'll be handled the app, if desired.
This is the same strategy Meta has used to ship React for years. The
React build itself has unminified symbols, but they get minified as part
of Meta's regular build pipeline.
Even if an app does not minify their npm dependencies, gzip covers most
of the cost of symbol renaming anyway.
This saves us from having to ship sourcemaps, which means even apps that
don't have sourcemaps configured will be able to debug the React build
as easily as they would any other npm dependency.
* Jest + test renderer helpers for concurrent mode
Most of our concurrent React tests use the noop renderer. But most
of those tests don't test the renderer API, and could instead be
written with the test renderer. We should switch to using the test
renderer whenever possible, because that's what we expect product devs
and library authors to do. If test renderer is sufficient for writing
most React core tests, it should be sufficient for others, too. (The
converse isn't true but we should aim to dogfood test renderer as much
as possible.)
This PR adds a new package, jest-react (thanks @cpojer). I've moved
our existing Jest matchers into that package and added some new ones.
I'm not expecting to figure out the final API in this PR. My goal is
to land something good enough that we can start dogfooding in www.
TODO: Continue migrating Suspense tests, decide on better API names
* Add additional invariants to prevent common errors
- Errors if user attempts to flush when log of yields is not empty
- Throws if argument passed to toClearYields is not ReactTestRenderer
* Better method names
- toFlushAll -> toFlushAndYield
- toFlushAndYieldThrough ->
- toClearYields -> toHaveYielded
Also added toFlushWithoutYielding
* Fix jest-react exports
* Tweak README
