Detect subscriptions wrapped in startTransition #22271
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acdlite
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eps1lon
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acdlite
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acdlite
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acdlite
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Summary: This sync includes the following changes: - **[f4ac680c7](facebook/react@f4ac680c7 )**: Fixed broken build script --unsafe-partial flag ([#22324](facebook/react#22324)) //<Brian Vaughn>// - **[67222f044](facebook/react@67222f044 )**: [Experiment] Warn if callback ref returns a function ([#22313](facebook/react#22313)) //<Dan Abramov>// - **[263cfa6ec](facebook/react@263cfa6ec )**: [Experimental] Add useInsertionEffect ([#21913](facebook/react#21913)) //<Ricky>// - **[806aaa2e2](facebook/react@806aaa2e2 )**: [useSES shim] Import prefixed native API ([#22310](facebook/react#22310)) //<Andrew Clark>// - **[fd5e01c2e](facebook/react@fd5e01c2e )**: [useSES/extra] Reuse old selection if possible ([#22307](facebook/react#22307)) //<Andrew Clark>// - **[33226fada](facebook/react@33226fada )**: Check for store mutations before commit ([#22290](facebook/react#22290)) //<Andrew Clark>// - **[86c7ca70a](facebook/react@86c7ca70a )**: Fix link ([#22296](facebook/react#22296)) //<Konstantin Popov>// - **[0fd195f29](facebook/react@0fd195f29 )**: update error message to include useLayoutEffect or useEffect on bad e… ([#22279](facebook/react#22279)) //<salazarm>// - **[8f96c6b2a](facebook/react@8f96c6b2a )**: [Bugfix] Prevent infinite update loop caused by a synchronous update in a passive effect ([#22277](facebook/react#22277)) //<Andrew Clark>// - **[4ce89a58d](facebook/react@4ce89a58d )**: Test bad useEffect return value with noop-renderer ([#22258](facebook/react#22258)) //<Sebastian Silbermann>// - **[a3fde2358](facebook/react@a3fde2358 )**: Detect subscriptions wrapped in startTransition ([#22271](facebook/react#22271)) //<salazarm>// Changelog: [General][Changed] - React Native sync for revisions 95d762e...e8feb11 jest_e2e[run_all_tests] Reviewed By: rickhanlonii Differential Revision: D30966369 fbshipit-source-id: 6c88e591005deb1fd93493628ef4695add49186c
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* Detect subscriptions wrapped in startTransition
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Summary
n React 18+, we will recommend against userspace subscription implementations, and instead direct users to one of our built-in APIs like useState, useReducer, useContext, and useSyncExternalStore.
Subscriptions are only a problem when they are used to schedule concurrent updates, so we only need to warn if a subscription is wrapped in startTransition.
We can use a heuristic: if a single startTransition call updates more than n unique fibers, there's likely a subscription.
In dev, you can put each fiber into a set, then at the end of the startTransition call, count how many are in the set and fire a warning if it exceeds the limit.
Let's use console.warn instead of console.error since this may be noisy. Let's also only warn the first time we detect a subscription.
How did you test this change?
Added a test case inside a new file ReactStartTransition