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Double Invoke Effects in __DEV__ #19523

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Sep 24, 2020
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lunaruan
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@lunaruan lunaruan commented Aug 4, 2020

This PR double invokes effects in __DEV__ mode.

We are thinking about unmounting layout and/or passive effects for a hidden tree. To understand potential issues with this, we want to double invoke effects. This PR changes the behavior in DEV when an effect runs from create() to create() -> destroy() -> create(). The effect cleanup function will still be called before the effect runs in both dev and prod. (Note: This change is purely for research for now as it is likely to break real code.)

Note: The change is fully behind a flag and does not affect any of the code on npm.

@facebook-github-bot facebook-github-bot added CLA Signed React Core Team Opened by a member of the React Core Team labels Aug 4, 2020
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sizebot commented Aug 4, 2020

Details of bundled changes.

Comparing: a99bf5c...b9b5750

react-dom

File Filesize Diff Gzip Diff Prev Size Current Size Prev Gzip Current Gzip ENV
react-dom.development.js 0.0% 0.0% 872.83 KB 872.83 KB 199.89 KB 199.9 KB NODE_DEV
ReactDOMForked-prod.js 0.0% 0.0% 386.13 KB 386.14 KB 71.33 KB 71.33 KB FB_WWW_PROD
react-dom-server.node.development.js 0.0% 0.0% 137.06 KB 137.06 KB 36.37 KB 36.37 KB NODE_DEV
react-dom.production.min.js 0.0% 0.0% 117.72 KB 117.72 KB 38.02 KB 38.03 KB NODE_PROD
ReactDOMForked-profiling.js 0.0% 0.0% 400.17 KB 400.18 KB 73.73 KB 73.73 KB FB_WWW_PROFILING
react-dom-server.browser.development.js 0.0% 0.0% 143.14 KB 143.14 KB 36.57 KB 36.57 KB UMD_DEV
react-dom-server.node.production.min.js 0.0% 0.0% 20.2 KB 20.2 KB 7.58 KB 7.58 KB NODE_PROD
ReactDOMTesting-dev.js 0.0% 0.0% 940.45 KB 940.45 KB 210.76 KB 210.76 KB FB_WWW_DEV
react-dom-test-utils.development.js 0.0% 0.0% 65.05 KB 65.05 KB 18.62 KB 18.62 KB NODE_DEV
ReactDOMTesting-prod.js 0.0% 0.0% 385.05 KB 385.05 KB 72.38 KB 72.38 KB FB_WWW_PROD
react-dom-test-utils.production.min.js 0.0% -0.0% 13.58 KB 13.58 KB 5.21 KB 5.21 KB NODE_PROD
ReactTestUtils-dev.js +0.1% +0.1% 59.7 KB 59.78 KB 16.56 KB 16.57 KB FB_WWW_DEV
react-dom.development.js 0.0% 0.0% 917.24 KB 917.24 KB 202.43 KB 202.43 KB UMD_DEV
react-dom.production.min.js 0.0% 0.0% 117.62 KB 117.62 KB 38.71 KB 38.71 KB UMD_PROD
react-dom.profiling.min.js 0.0% 0.0% 121.51 KB 121.51 KB 39.92 KB 39.92 KB UMD_PROFILING
ReactDOMForked-dev.js +0.6% +0.4% 988.64 KB 994.78 KB 219.16 KB 219.99 KB FB_WWW_DEV
react-dom.profiling.min.js 0.0% 0.0% 121.79 KB 121.79 KB 39.22 KB 39.22 KB NODE_PROFILING
react-dom-server.browser.production.min.js 0.0% 0.0% 19.88 KB 19.88 KB 7.46 KB 7.46 KB UMD_PROD
ReactDOM-dev.js 0.0% 0.0% 986.84 KB 986.92 KB 219.32 KB 219.34 KB FB_WWW_DEV
ReactDOM-prod.js 0.0% 0.0% 385.83 KB 385.83 KB 71.1 KB 71.1 KB FB_WWW_PROD
react-dom-server.browser.development.js 0.0% 0.0% 135.79 KB 135.79 KB 36.12 KB 36.12 KB NODE_DEV
ReactDOM-profiling.js 0.0% 0.0% 399.04 KB 399.04 KB 73.53 KB 73.53 KB FB_WWW_PROFILING
react-dom-server.browser.production.min.js 0.0% 0.0% 19.78 KB 19.78 KB 7.42 KB 7.42 KB NODE_PROD
ReactDOMServer-dev.js +0.1% +0.1% 145.53 KB 145.61 KB 37.29 KB 37.31 KB FB_WWW_DEV
react-dom-test-utils.development.js 0.0% 0.0% 70.21 KB 70.21 KB 19.11 KB 19.11 KB UMD_DEV

Size changes (stable)

Generated by 🚫 dangerJS against b9b5750

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sizebot commented Aug 4, 2020

Details of bundled changes.

Comparing: a99bf5c...b9b5750

react-dom

File Filesize Diff Gzip Diff Prev Size Current Size Prev Gzip Current Gzip ENV
react-dom.development.js 0.0% 0.0% 908.28 KB 908.28 KB 206.4 KB 206.4 KB NODE_DEV
ReactDOMForked-prod.js 0.0% 0.0% 374.8 KB 374.81 KB 69.54 KB 69.54 KB FB_WWW_PROD
react-dom-server.node.development.js 0.0% 0.0% 138.57 KB 138.57 KB 36.58 KB 36.59 KB NODE_DEV
react-dom.production.min.js 0.0% 0.0% 122.28 KB 122.28 KB 39.34 KB 39.34 KB NODE_PROD
ReactDOMForked-profiling.js 0.0% 0.0% 388.8 KB 388.81 KB 72 KB 72 KB FB_WWW_PROFILING
react-dom-server.browser.development.js 0.0% 0.0% 144.73 KB 144.73 KB 36.77 KB 36.77 KB UMD_DEV
react-dom-server.node.production.min.js 0.0% 0.0% 20.66 KB 20.66 KB 7.65 KB 7.65 KB NODE_PROD
ReactDOMTesting-dev.js 0.0% 0.0% 912.12 KB 912.12 KB 205.29 KB 205.29 KB FB_WWW_DEV
react-dom-test-utils.development.js 0.0% 0.0% 65.06 KB 65.06 KB 18.63 KB 18.63 KB NODE_DEV
react-dom-unstable-fizz.node.development.js 0.0% +0.1% 5.52 KB 5.52 KB 1.84 KB 1.84 KB NODE_DEV
react-dom-test-utils.production.min.js 0.0% -0.0% 13.59 KB 13.59 KB 5.22 KB 5.22 KB NODE_PROD
react-dom-unstable-fizz.browser.development.js 0.0% +0.1% 5.25 KB 5.25 KB 1.78 KB 1.78 KB UMD_DEV
react-dom-unstable-fizz.node.production.min.js 0.0% 🔺+0.3% 1.17 KB 1.17 KB 666 B 668 B NODE_PROD
react-dom-unstable-fizz.browser.production.min.js 0.0% 🔺+0.1% 1.22 KB 1.22 KB 712 B 713 B UMD_PROD
ReactTestUtils-dev.js +0.1% +0.1% 59.7 KB 59.78 KB 16.56 KB 16.58 KB FB_WWW_DEV
react-dom-unstable-fizz.browser.development.js 0.0% +0.1% 4.78 KB 4.78 KB 1.68 KB 1.68 KB NODE_DEV
react-dom.development.js 0.0% 0.0% 954.43 KB 954.43 KB 209.01 KB 209.01 KB UMD_DEV
react-dom-unstable-fizz.browser.production.min.js 0.0% 🔺+0.2% 1.01 KB 1.01 KB 616 B 617 B NODE_PROD
react-dom.production.min.js 0.0% 0.0% 122.11 KB 122.11 KB 40.09 KB 40.09 KB UMD_PROD
react-dom.profiling.min.js 0.0% 0.0% 127.36 KB 127.36 KB 41.76 KB 41.76 KB UMD_PROFILING
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react-dom.profiling.min.js 0.0% 0.0% 127.72 KB 127.72 KB 41.01 KB 41.02 KB NODE_PROFILING
ReactDOM-dev.js 0.0% 0.0% 961.26 KB 961.34 KB 214.66 KB 214.67 KB FB_WWW_DEV
ReactDOM-prod.js 0.0% -0.0% 374.58 KB 374.58 KB 69.39 KB 69.39 KB FB_WWW_PROD
react-dom-server.browser.development.js 0.0% 0.0% 137.3 KB 137.3 KB 36.33 KB 36.33 KB NODE_DEV
ReactDOM-profiling.js 0.0% 0.0% 387.74 KB 387.74 KB 71.82 KB 71.83 KB FB_WWW_PROFILING
react-dom-server.browser.production.min.js 0.0% 0.0% 20.24 KB 20.24 KB 7.5 KB 7.5 KB NODE_PROD
ReactDOMServer-dev.js +0.1% +0.1% 141.5 KB 141.58 KB 36.28 KB 36.3 KB FB_WWW_DEV
ReactDOMServer-prod.js 0.0% 0.0% 46.44 KB 46.44 KB 10.83 KB 10.83 KB FB_WWW_PROD
react-dom-test-utils.development.js 0.0% 0.0% 70.22 KB 70.22 KB 19.12 KB 19.12 KB UMD_DEV

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@bvaughn bvaughn self-assigned this Aug 4, 2020
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oriSomething commented Aug 6, 2020

It can cause some issues. For example, in where I work we have a component that have this kind of effect:

React.useEffect(() => {
  navigator.clipboard.readText().then(/* …And content to state variable  */);
}, []);

Also some components that sends analytics / fetch some data, which will probably break many tests.

EDIT:
We don't have proper cleanups always (What I wanted to say in short)

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bvaughn commented Aug 6, 2020

Also some components that sends analytics / fetch some data

I'm not sure if this is what you're saying, but you probably shouldn't be sending analytics in DEV mode (or you should be sending them somewhere different than production analytics).

As for your concern about testing, that's something I haven't thought much about. I can see where this might cause hassle.

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@bvaughn Well, the analytics is not about sending them. We have a logger of analytics (to browsers devtools console), so while developing we can make sure they logged in correct scenarios. If sometimes it called twice and sometimes once, we can't predict if analytics correct.

@vkurchatkin
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This looks like it might brake a lot of code. This changes implies that effects can only be used when they have very specific semantics: they should either be idempotent or reversible. Also it makes it a requirement to implement a cleanup even if it is never supposed to run.

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gaearon commented Aug 6, 2020

The change is fully behind a flag and does not affect any of the code on npm. Indeed, it is likely to break some code, so we want to try it at FB to see how large the impact is. We appreciate your concern but researching this more is the whole point of this PR. Hope this makes sense.

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gaearon commented Aug 6, 2020

I'll add though that [] effects are already invoked multiple times when you use Fast Refresh, for example. So it's a good idea to make things that truly must only happen once resistant to this, e.g. using a ref. Again, coming up with a specific guidance is still a part of the research. We need to balance the code that's already written with the tradeoffs of adding new valuable features.

@lunaruan lunaruan force-pushed the double_invoke branch 3 times, most recently from fe64e03 to e51e75b Compare August 12, 2020 23:28
@lunaruan
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Ready for review!

@lunaruan
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Updated the PR based on everyone's comments!

let fiber = firstChild;
while (fiber !== null) {
if (fiber.child !== null) {
// Should we add a separate subtree tag for this?
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What's this comment for? I'm not sure I understand it.

Is this pointing out the fact that we're going to end up traversing all of the subtree paths that have layout effects even if they're all updates and none of them are mounts? So we could add a DEV-only tag e.g. MountLayoutSubtreeTag or something.

Maybe we could add some additional clarification to the wording here.

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@lunaruan lunaruan Aug 22, 2020

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Yeah, I wasn't sure how OK it was to add a subtree tag vs. just traversing extra in DEV since it takes extra bytes to add an extra subtreetag, and I know at least with effectTag, we don't seem to want to add too many. If it's in DEV though it makes sense that it's OK. Thanks for clarifying!

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case ForwardRef:
case SimpleMemoComponent:
case Block: {
invokeGuardedCallback(
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Technically, after https://github.com/facebook/react/pull/19605/files this will be unnecessary since commitHookEffectListUnmount should be safe now.

It's an awkward inconsistency since the equivalent mount isn't safe. I don't know what the answer is.

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Hmm I'll leave it as is for now for consistency and maybe do a separate PR to make everything more consistent (Will creating a safelyCallCreate function cause perf issues)?

This was referenced Jun 30, 2024
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