pure #13748
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pure #13748
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A higher-order component version of the `React.PureComponent` class. During an update, the previous props are compared to the new props. If they are the same, React will skip rendering the component and its children. Unlike userspace implementations, `pure` will not add an additional fiber to the tree. The first argument must be a functional component; it does not work with classes. `pure` uses shallow comparison by default, like `React.PureComponent`. A custom comparison can be passed as the second argument. Co-authored-by: Andrew Clark <acdlite@fb.com> Co-authored-by: Sophie Alpert <sophiebits@fb.com>
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React: size: 🔺+0.9%, gzip: 🔺+0.8% ReactDOM: size: 🔺+0.6%, gzip: 🔺+0.7% Details of bundled changes.Comparing: 4d17c3f...645a8ba react
react-dom
react-art
react-test-renderer
react-reconciler
react-native-renderer
scheduler
Generated by 🚫 dangerJS |
sophiebits
approved these changes
Sep 27, 2018
| workInProgress.childExpirationTime = current.childExpirationTime; | ||
| if (pendingProps !== current.pendingProps) { |
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What's the significance of this change?
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Previously the expirationTime field represented the pending priority of props, state, and context. In the begin phase, we check if this is lower priority than the render priority. If so, we can bail out.
After this change, it represents only the pending priority of state and context. The props check is moved to the begin phase. That way, in the begin phase, we can distinguish between an update caused by props versus an update caused by state or context. pure will never bail out if state or context has changed.
| @@ -124,7 +127,7 @@ export function reconcileChildren( | |||
| current: Fiber | null, | |||
| workInProgress: Fiber, | |||
| nextChildren: any, | |||
| renderExpirationTime: ExpirationTime, | |||
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Why is this here? Did prettier change?
| if (isLegacyContextProvider(Component)) { | ||
| pushLegacyContextProvider(workInProgress); | ||
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| if (current !== null) { |
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I don't understand the significance of these changes either.
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Corresponds to the changes in https://github.com/facebook/react/pull/13748/files#r221093037
| } else { | ||
| const prototype = render.prototype; | ||
| if (!!(prototype && prototype.isReactComponent)) { | ||
| warningWithoutStack( |
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Unit tests for the warnings pls?
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sorry I could have also done this
sophiebits
reviewed
Sep 27, 2018
| ); | ||
| } | ||
| case PureComponentLazy: { |
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this duplication kills me a little bit :)
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you missed a golden opportunity to call this |
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It seems to be the first time React includes HOC in its public API. Do we need to expect some sort of new guides on when and how to use it? |
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Agree with @alexbaumgertner , but IMO they will do that but just seems don't have much time currently, so before the release there will be blog post |
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@acdlite Will DevTools need to be updated to recognize the new |
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@alexeyraspopov We always include guides/docs/etc with releases. This is not a release yet. |
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@acdlite Follow up facebook/react-devtools#1173 |
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Maybe I'm misremembering, but wasn't one of the design goals of SFC to be pure by default? |
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The goal was to make components easier to optimize. There are many ways to optimize, memoization based on shallow equality is just one possible optimization you can make. Functions already have less overhead since 16 (less property checks and memory usage), and they're also much more optimizable by compilers. Unfortunately our compilation experiments are still very early. |
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Thanks for the explainer @gaearon 😄 |
acdlite
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Oct 5, 2018
* pure A higher-order component version of the `React.PureComponent` class. During an update, the previous props are compared to the new props. If they are the same, React will skip rendering the component and its children. Unlike userspace implementations, `pure` will not add an additional fiber to the tree. The first argument must be a functional component; it does not work with classes. `pure` uses shallow comparison by default, like `React.PureComponent`. A custom comparison can be passed as the second argument. Co-authored-by: Andrew Clark <acdlite@fb.com> Co-authored-by: Sophie Alpert <sophiebits@fb.com> * Warn if first argument is not a functional component
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jetoneza
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Jan 23, 2019
* pure A higher-order component version of the `React.PureComponent` class. During an update, the previous props are compared to the new props. If they are the same, React will skip rendering the component and its children. Unlike userspace implementations, `pure` will not add an additional fiber to the tree. The first argument must be a functional component; it does not work with classes. `pure` uses shallow comparison by default, like `React.PureComponent`. A custom comparison can be passed as the second argument. Co-authored-by: Andrew Clark <acdlite@fb.com> Co-authored-by: Sophie Alpert <sophiebits@fb.com> * Warn if first argument is not a functional component
NMinhNguyen
referenced
this pull request
in enzymejs/react-shallow-renderer
Jan 29, 2020
* pure A higher-order component version of the `React.PureComponent` class. During an update, the previous props are compared to the new props. If they are the same, React will skip rendering the component and its children. Unlike userspace implementations, `pure` will not add an additional fiber to the tree. The first argument must be a functional component; it does not work with classes. `pure` uses shallow comparison by default, like `React.PureComponent`. A custom comparison can be passed as the second argument. Co-authored-by: Andrew Clark <acdlite@fb.com> Co-authored-by: Sophie Alpert <sophiebits@fb.com> * Warn if first argument is not a functional component
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Note: the discussion for this proposal is in reactjs/rfcs#63. It has since been renamed to
React.memo().A higher-order component version of the
React.PureComponentclass. During an update, the previous props are compared to the new props. If they are the same, React will skip rendering the component and its children.Unlike userspace implementations,
purewill not add an additional fiber to the tree.The first argument must be a functional component; it does not work with classes.
pureuses shallow comparison by default, likeReact.PureComponent. A custom comparison can be passed as the second argument.