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Merged
merged 1 commit into from
Jun 4, 2025
Merged

[pull] main from facebook:main #175

merged 1 commit into from
Jun 4, 2025

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@pull pull bot commented Jun 4, 2025

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Created by pull[bot] (v2.0.0-alpha.1)

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Stacked on #33403.

When a Promise is coming from React such as when it's passed from
another environment, we should forward the debug information from that
environment. We already do that when rendered as a child.

This makes it possible to also `await promise` and have the information
from that instrumented promise carry through to the next render.

This is a bit tricky because the current protocol is that we have to
read it from the Promise after it resolves so it has time to be assigned
to the promise. `async_hooks` doesn't pass us the instance (even though
it has it) when it gets resolved so we need to keep it around. However,
we have to be very careful because if we get this wrong it'll cause a
memory leak since we retain things by `asyncId` and then manually listen
for `destroy()` which can only be called once a Promise is GC:ed, which
it can't be if we retain it. We have to therefore use a `WeakRef` in
case it never resolves, and then read the `_debugInfo` when it resolves.
We could maybe install a setter or something instead but that's also
heavy.

The other issues is that we don't use native Promises in
ReactFlightClient so our instrumented promises aren't picked up by the
`async_hooks` implementation and so we never get a handle to our
thenable instance. To solve this we can create a native wrapper only in
DEV.
@pull pull bot added the ⤵️ pull label Jun 4, 2025
@pull pull bot merged commit 3705486 into code:main Jun 4, 2025
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