* Same as previous commit, but for Flare
I don't know what the public API for setting the event priority should
be. Right now it accepts a numeric enum, but is this what we want?
Maybe it should be a string enum? I've punted on this for now.
* Add test for hover events
* BUG: ReactPartialRenderer / New Context polutes mutable global state
The new context API stores the provided values on the shared context instance. When used in a synchronous context, this is not an issue. However when used in an concurrent context this can cause a "push provider" from one react render to have an effect on an unrelated concurrent react render.
I've encountered this bug in production when using renderToNodeStream, which asks ReactPartialRenderer for bytes up to a high water mark before yielding. If two Node Streams are created and read from in parallel, the state of one can polute the other.
I wrote a failing test to illustrate the conditions under which this happens.
I'm also concerned that the experimental concurrent/async React rendering on the client could suffer from the same issue.
* Use unique thread ID for each partial render to access Context
This first adds an allocator that keeps track of a unique ThreadID index
for each currently executing partial renderer. IDs are not just growing
but are reused as streams are destroyed.
This ensures that IDs are kept nice and compact.
This lets us use an "array" for each Context object to store the current
values. The look up for these are fast because they're just looking up
an offset in a tightly packed "array".
I don't use an actual Array object to store the values. Instead, I rely
on that VMs (notably V8) treat storage of numeric index property access
as a separate "elements" allocation.
This lets us avoid an extra indirection.
However, we must ensure that these arrays are not holey to preserve this
feature.
To do that I store the _threadCount on each context (effectively it takes
the place of the .length property on an array).
This lets us first validate that the context has enough slots before we
access the slot. If not, we fill in the slots with the default value.
* Don't stop context traversal at matching consumers
Originally, the idea was to time slice the traversal. This worked when
there was only a single context type per consumer.
Now that each fiber may have a list of context dependencies, including
duplicate entries, that optimization no longer makes sense – we could
end up scanning the same subtree multiple times.
* Remove changedBits from context object and stack
Don't need it anymore, yay
* Store list of contexts on the fiber
Currently, context can only be read by a special type of component,
ContextConsumer. We want to add support to all fibers, including
classes and functional components.
Each fiber may read from one or more contexts. To enable quick, mono-
morphic access of this list, we'll store them on a fiber property.
* Context.unstable_read
unstable_read can be called anywhere within the render phase. That
includes the render method, getDerivedStateFromProps, constructors,
functional components, and context consumer render props.
If it's called outside the render phase, an error is thrown.
* Remove vestigial context cursor
Wasn't being used.
* Split fiber.expirationTime into two separate fields
Currently, the `expirationTime` field represents the pending work of
both the fiber itself — including new props, state, and context — and of
any updates in that fiber's subtree.
This commit adds a second field called `childExpirationTime`. Now
`expirationTime` only represents the pending work of the fiber itself.
The subtree's pending work is represented by `childExpirationTime`.
The biggest advantage is it requires fewer checks to bailout on already
finished work. For most types of work, if the `expirationTime` does not
match the render expiration time, we can bailout immediately without
any further checks. This won't work for fibers that have
`shouldComponentUpdate` semantics (class components), for which we still
need to check for props and state changes explicitly.
* Performance nits
Optimize `readContext` for most common case
* Support concurrent primary and secondary renderers.
As a workaround to support multiple concurrent renderers, we categorize
some renderers as primary and others as secondary. We only expect
there to be two concurrent renderers at most: React Native (primary) and
Fabric (secondary); React DOM (primary) and React ART (secondary).
Secondary renderers store their context values on separate fields.
* Add back concurrent renderer warning
Only warn for two concurrent primary or two concurrent secondary renderers.
* Change "_secondary" suffix to "2"
#EveryBitCounts
