Track entangled lanes separately from update lane #27505
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I updated one of the tests related to synchronous popstate transitions to clarify what the desired behavior is. It's really about what happens if a popstate transition suspends. It should not cause an error, and the transition should be allowed to finish once the promise resolves. Ideally, if the transition suspends, it should completely revert back to the default behavior for transitions — i.e. it should no longer be treated as synchronous. Currently we don't do that, and when the promise resolve the transition will still be rendered synchronously, but we can improve this later.
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A small refactor to how the lane entanglement mechanism works. We can now distinguish between the lane that "spawned" a render task (i.e. a new update) versus the lanes that it's entangled with. Both the update lane and the entangled lanes will be included while rendering, but by keeping them separate, we don't lose the original priority. In practical terms, this means we can now entangle a low priority update with a higher priority lane while rendering at the lower priority. To do this, lanes that are entangled at the root are now tracked using the same variable that we use to track the "base lanes" when revealing a previously hidden tree — conceptually, they are the same thing. I also renamed this variable (from subtreeLanes to entangledRenderLanes) to better reflect how it's used. My primary motivation is related to useDeferredValue, which I'll address in a later PR.
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A small refactor to how the lane entanglement mechanism works. We can now distinguish between the lane that "spawned" a render task (i.e. a new update) versus the lanes that it's entangled with. Both the update lane and the entangled lanes will be included while rendering, but by keeping them separate, we don't lose the original priority. In practical terms, this means we can now entangle a low priority update with a higher priority lane while rendering at the lower priority. To do this, lanes that are entangled at the root are now tracked using the same variable that we use to track the "base lanes" when revealing a previously hidden tree — conceptually, they are the same thing. I also renamed this variable (from subtreeLanes to entangledRenderLanes) to better reflect how it's used. My primary motivation is related to useDeferredValue, which I'll address in a later PR. DiffTrain build for [309c8ad](309c8ad)
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Oct 17, 2023
### Based on #27505 If a parent render spawns a deferred task with useDeferredValue, but the parent render suspends, we should not wait for the parent render to complete before attempting to render the final value. The reason is that the initialValue argument to useDeferredValue is meant to represent an immediate preview of the final UI. If we can't render it "immediately", we might as well skip it and go straight to the "real" value. This is an improvement over how a userspace implementation of useDeferredValue would work, because a userspace implementation would have to wait for the parent task to commit (useEffect) before spawning the deferred task, creating a waterfall.
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### Based on #27505 If a parent render spawns a deferred task with useDeferredValue, but the parent render suspends, we should not wait for the parent render to complete before attempting to render the final value. The reason is that the initialValue argument to useDeferredValue is meant to represent an immediate preview of the final UI. If we can't render it "immediately", we might as well skip it and go straight to the "real" value. This is an improvement over how a userspace implementation of useDeferredValue would work, because a userspace implementation would have to wait for the parent task to commit (useEffect) before spawning the deferred task, creating a waterfall. DiffTrain build for [b2a68a6](b2a68a6)
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Oct 18, 2023
Update React from from 09fbee89d to a41957507. ### React upstream changes - facebook/react#27472 - facebook/react#27512 - facebook/react#27509 - facebook/react#27517 - facebook/react#27523 - facebook/react#27516 - facebook/react#27505
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### Based on facebook/react#27505 If a parent render spawns a deferred task with useDeferredValue, but the parent render suspends, we should not wait for the parent render to complete before attempting to render the final value. The reason is that the initialValue argument to useDeferredValue is meant to represent an immediate preview of the final UI. If we can't render it "immediately", we might as well skip it and go straight to the "real" value. This is an improvement over how a userspace implementation of useDeferredValue would work, because a userspace implementation would have to wait for the parent task to commit (useEffect) before spawning the deferred task, creating a waterfall. DiffTrain build for [b2a68a65c84b63ac86930d88ae5c84380cbbdeb6](facebook/react@b2a68a6)
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A small refactor to how the lane entanglement mechanism works. We can now distinguish between the lane that "spawned" a render task (i.e. a new update) versus the lanes that it's entangled with. Both the update lane and the entangled lanes will be included while rendering, but by keeping them separate, we don't lose the original priority. In practical terms, this means we can now entangle a low priority update with a higher priority lane while rendering at the lower priority. To do this, lanes that are entangled at the root are now tracked using the same variable that we use to track the "base lanes" when revealing a previously hidden tree — conceptually, they are the same thing. I also renamed this variable (from subtreeLanes to entangledRenderLanes) to better reflect how it's used. My primary motivation is related to useDeferredValue, which I'll address in a later PR.
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) ### Based on facebook#27505 If a parent render spawns a deferred task with useDeferredValue, but the parent render suspends, we should not wait for the parent render to complete before attempting to render the final value. The reason is that the initialValue argument to useDeferredValue is meant to represent an immediate preview of the final UI. If we can't render it "immediately", we might as well skip it and go straight to the "real" value. This is an improvement over how a userspace implementation of useDeferredValue would work, because a userspace implementation would have to wait for the parent task to commit (useEffect) before spawning the deferred task, creating a waterfall.
bigfootjon
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Apr 18, 2024
A small refactor to how the lane entanglement mechanism works. We can now distinguish between the lane that "spawned" a render task (i.e. a new update) versus the lanes that it's entangled with. Both the update lane and the entangled lanes will be included while rendering, but by keeping them separate, we don't lose the original priority. In practical terms, this means we can now entangle a low priority update with a higher priority lane while rendering at the lower priority. To do this, lanes that are entangled at the root are now tracked using the same variable that we use to track the "base lanes" when revealing a previously hidden tree — conceptually, they are the same thing. I also renamed this variable (from subtreeLanes to entangledRenderLanes) to better reflect how it's used. My primary motivation is related to useDeferredValue, which I'll address in a later PR. DiffTrain build for commit 309c8ad.
acdlite
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Aug 20, 2024
This is a refactor of the fix in facebook#27505. When a transition update is scheduled by a popstate event, (i.e. a back/ forward navigation) we attempt to render it synchronously even though it's a transition, since it's likely the previous page's data is cached. In facebook#27505, I changed the implementation so that it only "upgrades" the priority of the transition for a single attempt. If the attempt suspends, say because the data is not cached after all, from then on it should be treated as a normal transition. But it turns out facebook#27505 did not work as intended, because it relied on marking the root with pending synchronous work (root.pendingLanes), which was never cleared until the popstate update completed. The test scenarios I wrote accidentally worked for a different reason related to suspending the work loop, which I'm currently in the middle of refactoring.
acdlite
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Aug 20, 2024
This is a refactor of the fix in facebook#27505. When a transition update is scheduled by a popstate event, (i.e. a back/ forward navigation) we attempt to render it synchronously even though it's a transition, since it's likely the previous page's data is cached. In facebook#27505, I changed the implementation so that it only "upgrades" the priority of the transition for a single attempt. If the attempt suspends, say because the data is not cached after all, from then on it should be treated as a normal transition. But it turns out facebook#27505 did not work as intended, because it relied on marking the root with pending synchronous work (root.pendingLanes), which was never cleared until the popstate update completed. The test scenarios I wrote accidentally worked for a different reason related to suspending the work loop, which I'm currently in the middle of refactoring.
acdlite
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Aug 22, 2024
This is a refactor of the fix in facebook#27505. When a transition update is scheduled by a popstate event, (i.e. a back/ forward navigation) we attempt to render it synchronously even though it's a transition, since it's likely the previous page's data is cached. In facebook#27505, I changed the implementation so that it only "upgrades" the priority of the transition for a single attempt. If the attempt suspends, say because the data is not cached after all, from then on it should be treated as a normal transition. But it turns out facebook#27505 did not work as intended, because it relied on marking the root with pending synchronous work (root.pendingLanes), which was never cleared until the popstate update completed. The test scenarios I wrote accidentally worked for a different reason related to suspending the work loop, which I'm currently in the middle of refactoring.
acdlite
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Aug 23, 2024
This is a refactor of the fix in facebook#27505. When a transition update is scheduled by a popstate event, (i.e. a back/ forward navigation) we attempt to render it synchronously even though it's a transition, since it's likely the previous page's data is cached. In facebook#27505, I changed the implementation so that it only "upgrades" the priority of the transition for a single attempt. If the attempt suspends, say because the data is not cached after all, from then on it should be treated as a normal transition. But it turns out facebook#27505 did not work as intended, because it relied on marking the root with pending synchronous work (root.pendingLanes), which was never cleared until the popstate update completed. The test scenarios I wrote accidentally worked for a different reason related to suspending the work loop, which I'm currently in the middle of refactoring.
acdlite
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Aug 23, 2024
This is a refactor of the fix in #27505. When a transition update is scheduled by a popstate event, (i.e. a back/ forward navigation) we attempt to render it synchronously even though it's a transition, since it's likely the previous page's data is cached. In #27505, I changed the implementation so that it only "upgrades" the priority of the transition for a single attempt. If the attempt suspends, say because the data is not cached after all, from then on it should be treated as a normal transition. But it turns out #27505 did not work as intended, because it relied on marking the root with pending synchronous work (root.pendingLanes), which was never cleared until the popstate update completed. The test scenarios I wrote accidentally worked for a different reason related to suspending the work loop, which I'm currently in the middle of refactoring.
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This is a refactor of the fix in #27505. When a transition update is scheduled by a popstate event, (i.e. a back/ forward navigation) we attempt to render it synchronously even though it's a transition, since it's likely the previous page's data is cached. In #27505, I changed the implementation so that it only "upgrades" the priority of the transition for a single attempt. If the attempt suspends, say because the data is not cached after all, from then on it should be treated as a normal transition. But it turns out #27505 did not work as intended, because it relied on marking the root with pending synchronous work (root.pendingLanes), which was never cleared until the popstate update completed. The test scenarios I wrote accidentally worked for a different reason related to suspending the work loop, which I'm currently in the middle of refactoring. DiffTrain build for commit ee7f675.
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This is a refactor of the fix in #27505. When a transition update is scheduled by a popstate event, (i.e. a back/ forward navigation) we attempt to render it synchronously even though it's a transition, since it's likely the previous page's data is cached. In #27505, I changed the implementation so that it only "upgrades" the priority of the transition for a single attempt. If the attempt suspends, say because the data is not cached after all, from then on it should be treated as a normal transition. But it turns out #27505 did not work as intended, because it relied on marking the root with pending synchronous work (root.pendingLanes), which was never cleared until the popstate update completed. The test scenarios I wrote accidentally worked for a different reason related to suspending the work loop, which I'm currently in the middle of refactoring. DiffTrain build for [ee7f675](ee7f675)
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Aug 27, 2024
This is a refactor of the fix in facebook#27505. When a transition update is scheduled by a popstate event, (i.e. a back/ forward navigation) we attempt to render it synchronously even though it's a transition, since it's likely the previous page's data is cached. In facebook#27505, I changed the implementation so that it only "upgrades" the priority of the transition for a single attempt. If the attempt suspends, say because the data is not cached after all, from then on it should be treated as a normal transition. But it turns out facebook#27505 did not work as intended, because it relied on marking the root with pending synchronous work (root.pendingLanes), which was never cleared until the popstate update completed. The test scenarios I wrote accidentally worked for a different reason related to suspending the work loop, which I'm currently in the middle of refactoring.
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Feb 20, 2025
### Based on facebook/react#27505 If a parent render spawns a deferred task with useDeferredValue, but the parent render suspends, we should not wait for the parent render to complete before attempting to render the final value. The reason is that the initialValue argument to useDeferredValue is meant to represent an immediate preview of the final UI. If we can't render it "immediately", we might as well skip it and go straight to the "real" value. This is an improvement over how a userspace implementation of useDeferredValue would work, because a userspace implementation would have to wait for the parent task to commit (useEffect) before spawning the deferred task, creating a waterfall. DiffTrain build for commit facebook/react@b2a68a6.
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A small refactor to how the lane entanglement mechanism works. We can now distinguish between the lane that "spawned" a render task (i.e. a new update) versus the lanes that it's entangled with. Both the update lane and the entangled lanes will be included while rendering, but by keeping them separate, we don't lose the original priority.
In practical terms, this means we can now entangle a low priority update with a higher priority lane while rendering at the lower priority.
To do this, lanes that are entangled at the root are now tracked using the same variable that we use to track the "base lanes" when revealing a previously hidden tree — conceptually, they are the same thing. I also renamed this variable (from subtreeLanes to entangledRenderLanes) to better reflect how it's used.
My primary motivation is related to useDeferredValue, which I'll address in a later PR.