From 0dae8b55c5ef2d76eebf4dd747f414603ecb5f33 Mon Sep 17 00:00:00 2001 From: Andrew Clark Date: Sun, 18 Feb 2024 14:39:12 -0500 Subject: [PATCH] Move all markRef calls into begin phase MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Certain fiber types may have a ref attached to them. The main ones are HostComponent and ClassComponent. During the render phase, we check if a ref was passed to it, and if so, we schedule a Ref effect: `markRef`. Currently, we're not consistent about whether we call `markRef` in the begin phase or the complete phase. For some fiber types, I found that `markRef` was called in both phases, causing redundant work. After some investigation, I don't believe it's necessary to call `markRef` in both the begin phase and the complete phase, as long as you don't bail out before calling `markRef`. I though that maybe it had to do with the `attemptEarlyBailoutIfNoScheduledUpdates` branch, which is a fast path that skips the regular begin phase if no new props, state, or context were passed. But if the props haven't changed (referentially — the `memo` and `shouldComponentUpdate` checks happen later), then it follows that the ref couldn't have changed either. This is true even in the old `createElement` runtime where `ref` is stored on the element instead of as a prop, because there's no way to pass a new ref to an element without also passing new props. You might argue this is a leaky assumption, but since we're shifting ref to be just a regular prop anyway, I think it's the correct way to think about it going forward. I think the pattern of calling `markRef` in the complete phase may have been left over from an earlier iteration of the implementation before the bailout logic was structured like it is today. So, I removed all the `markRef` calls from the complete phase. In the case of ScopeComponent, which had no corresponding call in the begin phase, I added one. We already had a test that asserted that a ref is reattached even if the component bails out, but I added some new ones to be extra safe. The reason I'm changing this this is because I'm working on a different change to move the ref handling logic in `coerceRef` to happen in render phase of the component that accepts the ref, instead of during the parent's reconciliation. --- .../src/ReactFiberBeginWork.js | 4 +- .../src/ReactFiberCompleteWork.js | 38 +-------- .../src/__tests__/ReactFiberRefs-test.js | 83 +++++++++++++++++++ 3 files changed, 90 insertions(+), 35 deletions(-) create mode 100644 packages/react-reconciler/src/__tests__/ReactFiberRefs-test.js diff --git a/packages/react-reconciler/src/ReactFiberBeginWork.js b/packages/react-reconciler/src/ReactFiberBeginWork.js index a272da942e665..dff1dc5bc0905 100644 --- a/packages/react-reconciler/src/ReactFiberBeginWork.js +++ b/packages/react-reconciler/src/ReactFiberBeginWork.js @@ -1007,6 +1007,8 @@ function updateProfiler( } function markRef(current: Fiber | null, workInProgress: Fiber) { + // TODO: This is also where we should check the type of the ref and error if + // an invalid one is passed, instead of during child reconcilation. const ref = workInProgress.ref; if ( (current === null && ref !== null) || @@ -3531,7 +3533,7 @@ function updateScopeComponent( ) { const nextProps = workInProgress.pendingProps; const nextChildren = nextProps.children; - + markRef(current, workInProgress); reconcileChildren(current, workInProgress, nextChildren, renderLanes); return workInProgress.child; } diff --git a/packages/react-reconciler/src/ReactFiberCompleteWork.js b/packages/react-reconciler/src/ReactFiberCompleteWork.js index 639cec6cbf0d5..a2daff05de72e 100644 --- a/packages/react-reconciler/src/ReactFiberCompleteWork.js +++ b/packages/react-reconciler/src/ReactFiberCompleteWork.js @@ -75,8 +75,6 @@ import { } from './ReactWorkTags'; import {NoMode, ConcurrentMode, ProfileMode} from './ReactTypeOfMode'; import { - Ref, - RefStatic, Placement, Update, Visibility, @@ -186,10 +184,6 @@ function markUpdate(workInProgress: Fiber) { workInProgress.flags |= Update; } -function markRef(workInProgress: Fiber) { - workInProgress.flags |= Ref | RefStatic; -} - /** * In persistent mode, return whether this update needs to clone the subtree. */ @@ -1083,9 +1077,6 @@ function completeWork( // @TODO refactor this block to create the instance here in complete // phase if we are not hydrating. markUpdate(workInProgress); - if (workInProgress.ref !== null) { - markRef(workInProgress); - } if (nextResource !== null) { // This is a Hoistable Resource @@ -1120,9 +1111,6 @@ function completeWork( // and require an update markUpdate(workInProgress); } - if (current.ref !== workInProgress.ref) { - markRef(workInProgress); - } if (nextResource !== null) { // This is a Hoistable Resource // This must come at the very end of the complete phase. @@ -1194,10 +1182,6 @@ function completeWork( renderLanes, ); } - - if (current.ref !== workInProgress.ref) { - markRef(workInProgress); - } } else { if (!newProps) { if (workInProgress.stateNode === null) { @@ -1232,11 +1216,6 @@ function completeWork( workInProgress.stateNode = instance; markUpdate(workInProgress); } - - if (workInProgress.ref !== null) { - // If there is a ref on a host node we need to schedule a callback - markRef(workInProgress); - } } bubbleProperties(workInProgress); return null; @@ -1254,10 +1233,6 @@ function completeWork( newProps, renderLanes, ); - - if (current.ref !== workInProgress.ref) { - markRef(workInProgress); - } } else { if (!newProps) { if (workInProgress.stateNode === null) { @@ -1310,11 +1285,6 @@ function completeWork( markUpdate(workInProgress); } } - - if (workInProgress.ref !== null) { - // If there is a ref on a host node we need to schedule a callback - markRef(workInProgress); - } } bubbleProperties(workInProgress); @@ -1739,16 +1709,16 @@ function completeWork( workInProgress.stateNode = scopeInstance; prepareScopeUpdate(scopeInstance, workInProgress); if (workInProgress.ref !== null) { - markRef(workInProgress); + // Scope components always do work in the commit phase if there's a + // ref attached. markUpdate(workInProgress); } } else { if (workInProgress.ref !== null) { + // Scope components always do work in the commit phase if there's a + // ref attached. markUpdate(workInProgress); } - if (current.ref !== workInProgress.ref) { - markRef(workInProgress); - } } bubbleProperties(workInProgress); return null; diff --git a/packages/react-reconciler/src/__tests__/ReactFiberRefs-test.js b/packages/react-reconciler/src/__tests__/ReactFiberRefs-test.js new file mode 100644 index 0000000000000..a32b826597f22 --- /dev/null +++ b/packages/react-reconciler/src/__tests__/ReactFiberRefs-test.js @@ -0,0 +1,83 @@ +/** + * Copyright (c) Meta Platforms, Inc. and affiliates. + * + * This source code is licensed under the MIT license found in the + * LICENSE file in the root directory of this source tree. + * + * @emails react-core + */ + +'use strict'; + +let React; +let Scheduler; +let ReactNoop; +let act; +let assertLog; + +describe('ReactFiberRefs', () => { + beforeEach(() => { + jest.resetModules(); + React = require('react'); + Scheduler = require('scheduler'); + ReactNoop = require('react-noop-renderer'); + act = require('internal-test-utils').act; + assertLog = require('internal-test-utils').assertLog; + }); + + test('ref is attached even if there are no other updates (class)', async () => { + let component; + class Component extends React.PureComponent { + render() { + Scheduler.log('Render'); + component = this; + return 'Hi'; + } + } + + const ref1 = React.createRef(); + const ref2 = React.createRef(); + const root = ReactNoop.createRoot(); + + // Mount with ref1 attached + await act(() => root.render()); + assertLog(['Render']); + expect(root).toMatchRenderedOutput('Hi'); + expect(ref1.current).toBe(component); + // ref2 has no value + expect(ref2.current).toBe(null); + + // Switch to ref2, but don't update anything else. + await act(() => root.render()); + // The component did not re-render because no props changed. + assertLog([]); + expect(root).toMatchRenderedOutput('Hi'); + // But the refs still should have been swapped. + expect(ref1.current).toBe(null); + expect(ref2.current).toBe(component); + }); + + test('ref is attached even if there are no other updates (host component)', async () => { + // This is kind of ailly test because host components never bail out if they + // receive a new element, and there's no way to update a ref without also + // updating the props, but adding it here anyway for symmetry with the + // class case above. + const ref1 = React.createRef(); + const ref2 = React.createRef(); + const root = ReactNoop.createRoot(); + + // Mount with ref1 attached + await act(() => root.render(
Hi
)); + expect(root).toMatchRenderedOutput(
Hi
); + expect(ref1.current).not.toBe(null); + // ref2 has no value + expect(ref2.current).toBe(null); + + // Switch to ref2, but don't update anything else. + await act(() => root.render(
Hi
)); + expect(root).toMatchRenderedOutput(
Hi
); + // But the refs still should have been swapped. + expect(ref1.current).toBe(null); + expect(ref2.current).not.toBe(null); + }); +});