When Context change tracking was added to support modern Context it
relied on the "memoizedValue" to read the current value. This only works
in React 18+ when it was added to support Lazy Context Propagation.
However, the backend stored the old value the same way it used to work
for legacy Context in a global map. This was unnecessary since we *also*
have the old value on the previous Fiber.
This removes all the costly tracking of previous values for every Fiber
that uses Contexts slowing down profiling. Instead, we just compare the
Contexts from
The downside is that this no longer supports detecting changes due to
legacy Context because it doesn't have a similar "previous" value.
However, legacy Context has long been deprecated and is completely
removed in 19. So I don't think it's worth supporting since you have to
be on an old version *and* actually use legacy Context *and* trying to
profile something that updates it. Which btw, updating legacy contexts
only worked at all from 16 something when we made updates work. So it
was unusual even in the slight gap where you could and before you had
migrated to modern Context introduced in 16.3.
Updates useFormState to allow a sync function to be passed as an action.
A form action is almost always async, because it needs to talk to the
server. But since we support client-side actions, too, there's no reason
we can't allow sync actions, too.
I originally chose not to allow them to keep the implementation simpler
but it's not really that much more complicated because we already
support this for actions passed to startTransition. So now it's
consistent: anywhere an action is accepted, a sync client function is a
valid input.
Hermes parser is the preferred parser for Flow code going forward. We
need to upgrade to this parser to support new Flow syntax like function
`this` context type annotations or `ObjectType['prop']` syntax.
Unfortunately, there's quite a few upgrades here to make it work somehow
(dependencies between the changes)
- ~Upgrade `eslint` to `8.*`~ reverted this as the React eslint plugin
tests depend on the older version and there's a [yarn
bug](https://github.com/yarnpkg/yarn/issues/6285) that prevents
`devDependencies` and `peerDependencies` to different versions.
- Remove `eslint-config-fbjs` preset dependency and inline the rules,
imho this makes it a lot clearer what the rules are.
- Remove the turned off `jsx-a11y/*` rules and it's dependency instead
of inlining those from the `fbjs` config.
- Update parser and dependency from `babel-eslint` to `hermes-eslint`.
- `ft-flow/no-unused-expressions` rule replaces `no-unused-expressions`
which now allows standalone type asserts, e.g. `(foo: number);`
- Bunch of globals added to the eslint config
- Disabled `no-redeclare`, seems like the eslint upgrade started making
this more precise and warn against re-defined globals like
`__EXPERIMENTAL__` (in rollup scripts) or `fetch` (when importing fetch
from node-fetch).
- Minor lint fixes like duplicate keys in objects.
* Facebook -> Meta in copyright
rg --files | xargs sed -i 's#Copyright (c) Facebook, Inc. and its affiliates.#Copyright (c) Meta Platforms, Inc. and affiliates.#g'
* Manual tweaks
This PR adds the reactVersion pragma to tests.
Tests without the reactVersion pragma won't be run if the reactVersion pragma isn't specified.
Tested each React version manually with the pragma to make sure the tests pass
Note that this only fixes things for newer versions of React (e.g. 18 alpha). Older versions will remain broken because there's not a good way to read the most recent context value for a location in the tree after render has completed. This is because React maintains a stack of context values during render, but by the time DevTools is called– render has finished and the stack is empty.
