* allow nested `act()`s from different renderers
There are usecases where multiple renderers need to oprate inside an act() scope
- ReactDOM.render being used inside another component tree. The parent component will be rendered using ReactTestRenderer.create for a snapshot test or something.
- a ReactDOM instance interacting with a ReactTestRenderer instance (like for the new devtools)
This PR changes the way the acting sigils operate to allow for this. It keeps 2 booleans, one attached to React, one attached to the renderer. act() changes these values, and the workloop reads them to decide what warning to trigger.
I also renamed shouldWarnUnactedUpdates to warnsIfNotActing
* s/ReactIsActing/IsSomeRendererActing and s/ReactRendererIsActing/IsThisRendererActing
* use toWarnDev for dom fixture tests
forks toWarnDev from root into fixture/dom, updates tes tests to use it
* disable act() warnings for react-art()
- For 'secondary' renderers like react-act, we don't want to fire missing act() warnings; the wrapping renderer will fire warnings anyway, and when it flushes, it flushes effects *across* renderers.
- I could have used isPrimaryRenderer as the flag, but this is marked as false for react-test-renderer, and we *do* want the warning to fire for it. Hence a new flag.
* add missing dependency `art` to fixtures/dom
* [Scheduler] requestPaint
Signals to Scheduler that the browser needs to paint the screen. React
will call it in the commit phase. Scheduler will yield at the end of
the current frame, even if there is no pending input.
When `isInputPending` is not available, this has no effect, because we
yield at the end of every frame regardless.
React will call `requestPaint` in the commit phase as long as there's at
least one effect. We could choose not to call it if none of the effects
are DOM mutations, but this is so rare that it doesn't seem worthwhile
to bother checking.
* Fall back gracefully if requestPaint is missing
* Add Batched Mode
React has an unfortunate quirk where updates are sometimes synchronous
-- where React starts rendering immediately within the call stack of
`setState` — and sometimes batched, where updates are flushed at the
end of the current event. Any update that originates within the call
stack of the React event system is batched. This encompasses most
updates, since most updates originate from an event handler like
`onClick` or `onChange`. It also includes updates triggered by lifecycle
methods or effects. But there are also updates that originate outside
React's event system, like timer events, network events, and microtasks
(promise resolution handlers). These are not batched, which results in
both worse performance (multiple render passes instead of single one)
and confusing semantics.
Ideally all updates would be batched by default. Unfortunately, it's
easy for components to accidentally rely on this behavior, so changing
it could break existing apps in subtle ways.
One way to move to a batched-by-default model is to opt into Concurrent
Mode (still experimental). But Concurrent Mode introduces additional
semantic changes that apps may not be ready to adopt.
This commit introduces an additional mode called Batched Mode. Batched
Mode enables a batched-by-default model that defers all updates to the
next React event. Once it begins rendering, React will not yield to
the browser until the entire render is finished.
Batched Mode is superset of Strict Mode. It fires all the same warnings.
It also drops the forked Suspense behavior used by Legacy Mode, in favor
of the proper semantics used by Concurrent Mode.
I have not added any public APIs that expose the new mode yet. I'll do
that in subsequent commits.
* Suspense in Batched Mode
Should have same semantics as Concurrent Mode.
* Use RootTag field to configure type of root
There are three types of roots: Legacy, Batched, and Concurrent.
* flushSync should not flush batched work
Treat Sync and Batched expiration times separately. Only Sync updates
are pushed to our internal queue of synchronous callbacks.
Renamed `flushImmediateQueue` to `flushSyncCallbackQueue` for clarity.
* Import Scheduler directly, not via host config
We currently schedule asynchronous tasks via the host config. (The host
config is a static/build-time dependency injection system that varies
across different renderers — DOM, native, test, and so on.) Instead of
calling platform APIs like `requestIdleCallback` directly, each renderer
implements a method called `scheduleDeferredCallback`.
We've since discovered that when scheduling tasks, it's crucial that
React work is placed in the same queue as other, non-React work on the
main thread. Otherwise, you easily end up in a starvation scenario where
rendering is constantly interrupted by less important tasks. You need a
centralized coordinator that is used both by React and by other
frameworks and application code. This coordinator must also have a
consistent API across all the different host environments, for
convention's sake and so product code is portable — e.g. so the same
component can work in both React Native and React Native Web.
This turned into the Scheduler package. We will have different builds of
Scheduler for each of our target platforms. With this approach, we treat
Scheduler like a built-in platform primitive that exists wherever React
is supported.
Now that we have this consistent interface, the indirection of the host
config no longer makes sense for the purpose of scheduling tasks. In
fact, we explicitly do not want renderers to scheduled task via any
system except the Scheduler package.
So, this PR removes `scheduleDeferredCallback` and its associated
methods from the host config in favor of directly importing Scheduler.
* Missed an extraneous export
* Swap expect(ReactNoop) for expect(Scheduler)
In the previous commits, I upgraded our custom Jest matchers for the
noop and test renderers to use Scheduler under the hood.
Now that all these matchers are using Scheduler, we can drop
support for passing ReactNoop and test roots and always pass
Scheduler directly.
* Externalize Scheduler in noop and test bundles
I also noticed we don't need to regenerator runtime in noop anymore.
* Throw in tests if work is done before emptying log
Test renderer already does this. Makes it harder to miss unexpected
behavior by forcing you to assert on every logged value.
* Convert ReactNoop tests to use jest matchers
The matchers warn if work is flushed while the log is empty. This is
the pattern we already follow for test renderer. I've used the same APIs
as test renderer, so it should be easy to switch between the two.
* Avoid importing Scheduler directly
The reconciler should not depend directly on Scheduler. This adds it to
the host config for the renderer instead.
(Except for `scheduler/tracing` imports, which are used only by the
profiling build. I've left those imports as-is, though I'm open to
directing those through the host config, too.)
* Make throwaway root id longer to appease Brian
Specifying the directory as part of the `repository` field in a `package.json`
allows third party tools to provide better support when working with monorepos.
For example, it allows them to correctly construct a commit diff for a specific
package.
This format was accepted by npm in https://github.com/npm/rfcs/pull/19.
Whenever we do this, Rollup needs to materialize this as an object.
This causes it to also add the Babel compatibility property which is
unnecessary bloat. However, since when we use these, we leak the object
this often also deopts any compiler optimizations.
If we really need an object we should export default an object.
Currently there is an exception for DOMTopLevelEventTypes since
listing out the imports is a PITA and it doesn't escape so it should
get properly inlined. We should probably move to a different pattern
to avoid this for consistency though.
* [scheduler] Deadline object -> shouldYield
Instead of using a requestIdleCallback-style deadline object, expose a
method Scheduler.shouldYield that returns true if there's a higher
priority event in the queue.
* Nits
* Store the start time on `updateQueue` instead of `stateNode`
Originally I did this to free the `stateNode` field to store a second
set of children. I don't we'll need this anymore, since we use fragment
fibers instead. But I still think using `updateQueue` makes more sense
so I'll leave this in.
* Use fragment fibers to keep the primary and fallback children separate
If the children timeout, we switch to showing the fallback children in
place of the "primary" children. However, we don't want to delete the
primary children because then their state will be lost (both the React
state and the host state, e.g. uncontrolled form inputs). Instead we
keep them mounted and hide them. Both the fallback children AND the
primary children are rendered at the same time. Once the primary
children are un-suspended, we can delete the fallback children — don't
need to preserve their state.
The two sets of children are siblings in the host environment, but
semantically, for purposes of reconciliation, they are two separate
sets. So we store them using two fragment fibers.
However, we want to avoid allocating extra fibers for every placeholder.
They're only necessary when the children time out, because that's the
only time when both sets are mounted.
So, the extra fragment fibers are only used if the children time out.
Otherwise, we render the primary children directly. This requires some
custom reconciliation logic to preserve the state of the primary
children. It's essentially a very basic form of re-parenting.
* Use `memoizedState` to store various pieces of SuspenseComponent's state
SuspenseComponent has three pieces of state:
- alreadyCaptured: Whether a component in the child subtree already
suspended. If true, subsequent suspends should bubble up to the
next boundary.
- didTimeout: Whether the boundary renders the primary or fallback
children. This is separate from `alreadyCaptured` because outside of
strict mode, when a boundary times out, the first commit renders the
primary children in an incomplete state, then performs a second commit
to switch the fallback. In that first commit, `alreadyCaptured` is
false and `didTimeout` is true.
- timedOutAt: The time at which the boundary timed out. This is separate
from `didTimeout` because it's not set unless the boundary
actually commits.
These were previously spread across several fields.
This happens to make the non-strict case a bit less hacky; the logic for
that special case is now mostly localized to the UnwindWork module.
* Hide timed-out Suspense children
When a subtree takes too long to load, we swap its contents out for
a fallback to unblock the rest of the tree. Because we don't want
to lose the state of the timed out view, we shouldn't actually delete
the nodes from the tree. Instead, we'll keep them mounted and hide
them visually. When the subtree is unblocked, we un-hide it, having
preserved the existing state.
Adds additional host config methods. For mutation mode:
- hideInstance
- hideTextInstance
- unhideInstance
- unhideTextInstance
For persistent mode:
- cloneHiddenInstance
- cloneUnhiddenInstance
- createHiddenTextInstance
I've only implemented the new methods in the noop and test renderers.
I'll implement them in the other renderers in subsequent commits.
* Include `hidden` prop in noop renderer's output
This will be used in subsequent commits to test that timed-out children
are properly hidden.
Also adds getChildrenAsJSX() method as an alternative to using
getChildren(). (Ideally all our tests would use test renderer #oneday.)
* Implement hide/unhide host config methods for DOM renderer
For DOM nodes, we hide using `el.style.display = 'none'`.
Text nodes don't have style, so we hide using `text.textContent = ''`.
* Implement hide/unhide host config methods for Art renderer
* Create DOM fixture that tests state preservation of timed out content
* Account for class components that suspend outside concurrent mode
Need to distinguish mount from update. An unfortunate edge case :(
* Fork appendAllChildren between persistent and mutation mode
* Remove redundant check for existence of el.style
* Schedule placement effect on indeterminate components
In non-concurrent mode, indeterminate fibers may commit in an
inconsistent state. But when they update, we should throw out the
old fiber and start fresh. Which means the new fiber needs a
placement effect.
* Pass null instead of current everywhere in mountIndeterminateComponent
All of these features are based on features of React's internal
scheduler. The eventual goal is to lift as much as possible out of the
React internals into the Scheduler package.
Includes some renaming of existing methods.
- `scheduleWork` is now `scheduleCallback`
- `cancelScheduledWork` is now `cancelCallback`
Priority levels
---------------
Adds the ability to schedule callbacks at different priority levels.
The current levels are (final names TBD):
- Immediate priority. Fires at the end of the outermost currently
executing (similar to a microtask).
- Interactive priority. Fires within a few hundred milliseconds. This
should only be used to provide quick feedback to the user as a result
of an interaction.
- Normal priority. This is the default. Fires within several seconds.
- "Maybe" priority. Only fires if there's nothing else to do. Used for
prerendering or warming a cache.
The priority is changed using `runWithPriority`:
```js
runWithPriority(InteractivePriority, () => {
scheduleCallback(callback);
});
```
Continuations
-------------
Adds the ability for a callback to yield without losing its place
in the queue, by returning a continuation. The continuation will have
the same expiration as the callback that yielded.
Wrapped callbacks
-----------------
Adds the ability to wrap a callback so that, when it is called, it
receives the priority of the current execution context.
