[WIP] [simple-cache-provider] Subscriptions #13216
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React: size: 🔺+2.4%, gzip: 🔺+1.9% ReactDOM: size: 🔺+0.7%, gzip: 🔺+0.7% Details of bundled changes.Comparing: 21ac62c...0830626 react
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react-test-renderer
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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.
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.
Wasn't being used.
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.
Adds subscription support. A subscription is created the first time a value is read from the cache, and disposed once we detect that all the consumers have unmounted. On the initial mount, subscriptions are stored in a special map on the nearest provider (`_pendingChildSubscriptionsMap`). When the initial mount commits, the subscriptions are transferred from the pending set to the newly mounted provider.
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Closed in favor of #13337 |
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Depends on #13139
Adds subscription support to simple-cache-provider. A subscription is created the first time a value is read from the cache, and disposed once we detect that all the consumers have unmounted.
On the initial mount, subscriptions are stored in a special map on the nearest provider (
_pendingChildSubscriptionsMap). When the initial mount commits, the subscriptions are transferred from the pending set to the newly mounted provider.The advantage of this approach over the one used by the create-subscription package (and most third-party libraries) is that the context API is used to ensure consistency: if multiple components read the same value from the cache, they will always receive the same value. Subscriptions are created per key, not per component.
Because consistency is guaranteed between components, it's ok if the tree is out of sync with the latest subscription value. We never have to revert back to sync mode. In other words, the React tree is eventually consistent with the subscription, but multiple components within a single React tree are always consistent with each other.
TODO:
cache.purgecache.preloadcalculateChangedBitsAPI to optimize subscription updatesFollow ups: