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Andrew Clark
2b509e2c8c
* Store list of contexts on the fiber 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. * Context.unstable_read 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. * Remove vestigial context cursor Wasn't being used. * Split fiber.expirationTime into two separate fields 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. * Performance nits Optimize `readContext` for most common case