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List reconciliation #51980

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3778496
feat(core): add new list reconcilation algorithm
pkozlowski-opensource Oct 3, 2023
028a6f0
feat(core): the new list reconciliation algorithm for built-in for
pkozlowski-opensource Oct 3, 2023
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142 changes: 73 additions & 69 deletions packages/core/src/render3/instructions/control_flow.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -6,16 +6,18 @@
* found in the LICENSE file at https://angular.io/license
*/

import {DefaultIterableDiffer, IterableChangeRecord, TrackByFunction} from '../../change_detection';
import {TrackByFunction} from '../../change_detection';
import {DehydratedContainerView} from '../../hydration/interfaces';
import {findMatchingDehydratedView} from '../../hydration/views';
import {assertDefined} from '../../util/assert';
import {assertLContainer, assertLView, assertTNode} from '../assert';
import {bindingUpdated} from '../bindings';
import {CONTAINER_HEADER_OFFSET, LContainer} from '../interfaces/container';
import {ComponentTemplate} from '../interfaces/definition';
import {TNode} from '../interfaces/node';
import {CONTEXT, DECLARATION_COMPONENT_VIEW, HEADER_OFFSET, LView, TVIEW, TView} from '../interfaces/view';
import {detachView} from '../node_manipulation';
import {CONTEXT, DECLARATION_COMPONENT_VIEW, HEADER_OFFSET, HYDRATION, LView, TVIEW, TView} from '../interfaces/view';
import {LiveCollection, reconcile} from '../list_reconciliation';
import {destroyLView, detachView} from '../node_manipulation';
import {getLView, nextBindingIndex} from '../state';
import {getTNode} from '../util/view_utils';
import {addLViewToLContainer, createAndRenderEmbeddedLView, getLViewFromLContainer, removeLViewFromLContainer, shouldAddViewToDom} from '../view_manipulation';
Expand Down Expand Up @@ -99,7 +101,7 @@ export function ɵɵrepeaterTrackByIdentity<T>(_: number, value: T) {
}

class RepeaterMetadata {
constructor(public hasEmptyBlock: boolean, public differ: DefaultIterableDiffer<unknown>) {}
constructor(public hasEmptyBlock: boolean, public trackByFn: TrackByFunction<unknown>) {}
}

/**
Expand Down Expand Up @@ -135,7 +137,7 @@ export function ɵɵrepeaterCreate(
// new function. For pure functions it's not necessary.
trackByFn.bind(hostLView[DECLARATION_COMPONENT_VIEW][CONTEXT]) :
trackByFn;
const metadata = new RepeaterMetadata(hasEmptyBlock, new DefaultIterableDiffer(boundTrackBy));
const metadata = new RepeaterMetadata(hasEmptyBlock, boundTrackBy);
hostLView[HEADER_OFFSET + index] = metadata;

ɵɵtemplate(index + 1, templateFn, decls, vars);
Expand All @@ -150,6 +152,48 @@ export function ɵɵrepeaterCreate(
}
}

class LiveCollectionLContainerImpl extends
LiveCollection<LView<RepeaterContext<unknown>>, RepeaterContext<unknown>> {
constructor(
private lContainer: LContainer, private hostLView: LView, private templateTNode: TNode,
private trackByFn: TrackByFunction<unknown>) {
super();
}

override get length(): number {
return this.lContainer.length - CONTAINER_HEADER_OFFSET;
}
override at(index: number): LView<RepeaterContext<unknown>> {
return getExistingLViewFromLContainer(this.lContainer, index);
}
override key(index: number): unknown {
return this.trackByFn(index, this.at(index)[CONTEXT].$implicit);
}
override attach(index: number, lView: LView<RepeaterContext<unknown>>): void {
const dehydratedView = lView[HYDRATION] as DehydratedContainerView;
addLViewToLContainer(
this.lContainer, lView, index, shouldAddViewToDom(this.templateTNode, dehydratedView));
}
override detach(index: number): LView<RepeaterContext<unknown>> {
return detachExistingView<RepeaterContext<unknown>>(this.lContainer, index);
}
override create(index: number, value: unknown): LView<RepeaterContext<unknown>> {
const dehydratedView =
findMatchingDehydratedView(this.lContainer, this.templateTNode.tView!.ssrId);
const embeddedLView = createAndRenderEmbeddedLView(
this.hostLView, this.templateTNode, new RepeaterContext(this.lContainer, value, index),
{dehydratedView});

return embeddedLView;
}
override destroy(lView: LView<RepeaterContext<unknown>>): void {
destroyLView(lView[TVIEW], lView);
}
override updateValue(index: number, value: unknown): void {
this.at(index)[CONTEXT].$implicit = value;
}
}

/**
* The repeater instruction does update-time diffing of a provided collection (against the
* collection seen previously) and maps changes in the collection to views structure (by adding,
Expand All @@ -165,79 +209,43 @@ export function ɵɵrepeater(
const hostLView = getLView();
const hostTView = hostLView[TVIEW];
const metadata = hostLView[HEADER_OFFSET + metadataSlotIdx] as RepeaterMetadata;
const containerIndex = metadataSlotIdx + 1;
const lContainer = getLContainer(hostLView, HEADER_OFFSET + containerIndex);
const itemTemplateTNode = getExistingTNode(hostTView, containerIndex);

const differ = metadata.differ;
const changes = differ.diff(collection);

// handle repeater changes
if (changes !== null) {
const containerIndex = metadataSlotIdx + 1;
const itemTemplateTNode = getExistingTNode(hostTView, containerIndex);
const lContainer = getLContainer(hostLView, HEADER_OFFSET + containerIndex);
let needsIndexUpdate = false;
changes.forEachOperation(
(item: IterableChangeRecord<unknown>, adjustedPreviousIndex: number|null,
currentIndex: number|null) => {
if (item.previousIndex === null) {
// add
const newViewIdx = adjustToLastLContainerIndex(lContainer, currentIndex);
const dehydratedView =
findMatchingDehydratedView(lContainer, itemTemplateTNode.tView!.ssrId);
const embeddedLView = createAndRenderEmbeddedLView(
hostLView, itemTemplateTNode,
new RepeaterContext(lContainer, item.item, newViewIdx), {dehydratedView});
addLViewToLContainer(
lContainer, embeddedLView, newViewIdx,
shouldAddViewToDom(itemTemplateTNode, dehydratedView));
needsIndexUpdate = true;
} else if (currentIndex === null) {
// remove
adjustedPreviousIndex = adjustToLastLContainerIndex(lContainer, adjustedPreviousIndex);
removeLViewFromLContainer(lContainer, adjustedPreviousIndex);
needsIndexUpdate = true;
} else if (adjustedPreviousIndex !== null) {
// move
const existingLView =
detachExistingView<RepeaterContext<unknown>>(lContainer, adjustedPreviousIndex);
addLViewToLContainer(lContainer, existingLView, currentIndex);
needsIndexUpdate = true;
}
});

// A trackBy function might return the same value even if the underlying item changed - re-bind
// it in the context.
changes.forEachIdentityChange((record: IterableChangeRecord<unknown>) => {
const viewIdx = adjustToLastLContainerIndex(lContainer, record.currentIndex);
const lView = getExistingLViewFromLContainer<RepeaterContext<unknown>>(lContainer, viewIdx);
lView[CONTEXT].$implicit = record.item;
});
reconcile(
new LiveCollectionLContainerImpl(
lContainer, hostLView, itemTemplateTNode, metadata.trackByFn),
collection, metadata.trackByFn);

// moves in the container might caused context's index to get out of order, re-adjust
if (needsIndexUpdate) {
for (let i = 0; i < lContainer.length - CONTAINER_HEADER_OFFSET; i++) {
const lView = getExistingLViewFromLContainer<RepeaterContext<unknown>>(lContainer, i);
lView[CONTEXT].$index = i;
}
}
// moves in the container might caused context's index to get out of order, re-adjust
// PERF: we could try to book-keep moves and do this index re-adjust as need, at the cost of the
// additional code complexity
for (let i = 0; i < lContainer.length - CONTAINER_HEADER_OFFSET; i++) {
const lView = getExistingLViewFromLContainer<RepeaterContext<unknown>>(lContainer, i);
lView[CONTEXT].$index = i;
}

// handle empty blocks
// PERF: maybe I could skip allocation of memory for the empty block? Isn't it the "fix" on the
// compiler side that we've been discussing? Talk to K & D!
const bindingIndex = nextBindingIndex();
if (metadata.hasEmptyBlock) {
const hasItemsInCollection = differ.length > 0;
if (bindingUpdated(hostLView, bindingIndex, hasItemsInCollection)) {
const isCollectionEmpty = lContainer.length - CONTAINER_HEADER_OFFSET === 0;
if (bindingUpdated(hostLView, bindingIndex, isCollectionEmpty)) {
const emptyTemplateIndex = metadataSlotIdx + 2;
const lContainer = getLContainer(hostLView, HEADER_OFFSET + emptyTemplateIndex);
if (hasItemsInCollection) {
removeLViewFromLContainer(lContainer, 0);
} else {
const lContainerForEmpty = getLContainer(hostLView, HEADER_OFFSET + emptyTemplateIndex);
if (isCollectionEmpty) {
const emptyTemplateTNode = getExistingTNode(hostTView, emptyTemplateIndex);
const dehydratedView =
findMatchingDehydratedView(lContainer, emptyTemplateTNode.tView!.ssrId);
findMatchingDehydratedView(lContainerForEmpty, emptyTemplateTNode.tView!.ssrId);
const embeddedLView = createAndRenderEmbeddedLView(
hostLView, emptyTemplateTNode, undefined, {dehydratedView});
addLViewToLContainer(
lContainer, embeddedLView, 0, shouldAddViewToDom(emptyTemplateTNode, dehydratedView));
lContainerForEmpty, embeddedLView, 0,
shouldAddViewToDom(emptyTemplateTNode, dehydratedView));
} else {
removeLViewFromLContainer(lContainerForEmpty, 0);
}
}
}
Expand All @@ -250,10 +258,6 @@ function getLContainer(lView: LView, index: number): LContainer {
return lContainer;
}

function adjustToLastLContainerIndex(lContainer: LContainer, index: number|null): number {
return index !== null ? index : lContainer.length - CONTAINER_HEADER_OFFSET;
}

function detachExistingView<T>(lContainer: LContainer, index: number): LView<T> {
const existingLView = detachView(lContainer, index);
ngDevMode && assertLView(existingLView);
Expand Down
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