refactor(ivy): LView is a proper linked list (#28382)

- TView no longer stores childIndex
- LView now as CHILD_HEAD and CHILD_TAIL

TView used to store the head of the list, therefor all LViews had to have the same head, which is incorrect.

PR Close #28382

packages/core/src/render3/component_ref.ts

@@ -190,7 +190,7 @@ export class ComponentFactory<T> extends viewEngine_ComponentFactory<T> {
       component = createRootComponent(
           componentView, this.componentDef, rootLView, rootContext, [LifecycleHooksFeature]);
 
-      addToViewTree(rootLView, HEADER_OFFSET, componentView);
+      addToViewTree(rootLView, componentView);
       refreshDescendantViews(rootLView);
     } finally {
       leaveView(oldLView);

packages/core/src/render3/discovery_utils.ts

@@ -101,9 +101,7 @@ export function getViewComponent<T = {}>(element: Element | {}): T|null {
   ngDevMode && assertLView(lView);
   while (lView[HOST] === null && (parent = getLViewParent(lView) !)) {
     // As long as lView[HOST] is null we know we are part of sub-template such as `*ngIf`
-    if (parent) {
-      lView = parent;
-    }
+    lView = parent;
   }
   return lView[FLAGS] & LViewFlags.IsRoot ? null : lView[CONTEXT] as T;
 }

packages/core/src/render3/instructions.ts

@@ -36,7 +36,7 @@ import {SanitizerFn} from './interfaces/sanitization';
 import {StylingContext} from './interfaces/styling';
 import {BINDING_INDEX, CHILD_HEAD, CHILD_TAIL, CLEANUP, CONTEXT, DECLARATION_VIEW, ExpandoInstructions, FLAGS, HEADER_OFFSET, HOST, INJECTOR, InitPhaseState, LView, LViewFlags, NEXT, OpaqueViewState, PARENT, QUERIES, RENDERER, RENDERER_FACTORY, RootContext, RootContextFlags, SANITIZER, TData, TVIEW, TView, T_HOST} from './interfaces/view';
 import {assertNodeOfPossibleTypes, assertNodeType} from './node_assert';
-import {appendChild, appendProjectedNode, createTextNode, getLViewChild, insertView, removeView} from './node_manipulation';
+import {appendChild, appendProjectedNode, createTextNode, insertView, removeView} from './node_manipulation';
 import {isNodeMatchingSelectorList, matchingSelectorIndex} from './node_selector_matcher';
 import {decreaseElementDepthCount, enterView, getBindingsEnabled, getCheckNoChangesMode, getContextLView, getCurrentDirectiveDef, getElementDepthCount, getIsParent, getLView, getPreviousOrParentTNode, increaseElementDepthCount, isCreationMode, leaveView, nextContextImpl, resetComponentState, setBindingRoot, setCheckNoChangesMode, setCurrentDirectiveDef, setCurrentQueryIndex, setIsParent, setPreviousOrParentTNode,} from './state';
 import {getInitialClassNameValue, getInitialStyleStringValue, initializeStaticContext as initializeStaticStylingContext, patchContextWithStaticAttrs, renderInitialClasses, renderInitialStyles, renderStyling, updateClassProp as updateElementClassProp, updateContextWithBindings, updateStyleProp as updateElementStyleProp, updateStylingMap} from './styling/class_and_style_bindings';
@@ -788,7 +788,6 @@ export function createTView(
     viewQuery: viewQuery,
     node: null !,
     data: blueprint.slice().fill(null, bindingStartIndex),
-    childIndex: -1,  // Children set in addToViewTree(), if any
     bindingStartIndex: bindingStartIndex,
     viewQueryStartIndex: initialViewLength,
     expandoStartIndex: initialViewLength,
@@ -2373,7 +2372,7 @@ export function containerRefreshEnd(): void {
  * by executing an associated template function.
  */
 function refreshDynamicEmbeddedViews(lView: LView) {
-  for (let current = getLViewChild(lView); current !== null; current = current[NEXT]) {
+  for (let current = lView[CHILD_HEAD]; current !== null; current = current[NEXT]) {
     // Note: current can be an LView or an LContainer instance, but here we are only interested
     // in LContainer. We can tell it's an LContainer because its length is less than the LView
     // header.
@@ -2704,13 +2703,14 @@ export function projection(nodeIndex: number, selectorIndex: number = 0, attrs?:
  *
  * @param lView The view where LView or LContainer should be added
  * @param adjustedHostIndex Index of the view's host node in LView[], adjusted for header
- * @param state The LView or LContainer to add to the view tree
+ * @param lViewOrLContainer The LView or LContainer to add to the view tree
  * @returns The state passed in
  */
 export function addToViewTree<T extends LView|LContainer>(lView: LView, lViewOrLContainer: T): T {
   // TODO(benlesh/misko): This implementation is incorrect, because it always adds the LContainer to
-  // the end of the queue, which means if the developer asks for the LContainers out of order, the
-  // change detection will run out of order.
+  // the end of the queue, which means if the developer retrieves the LContainers from RNodes out of
+  // order, the change detection will run out of order, as the act of retrieving the the LContainer
+  // from the RNode is what adds it to the queue.
   if (lView[CHILD_HEAD]) {
     lView[CHILD_TAIL] ![NEXT] = lViewOrLContainer;
   } else {

packages/core/src/render3/interfaces/view.ts

@@ -46,7 +46,7 @@ export const CHILD_TAIL = 15;
 export const CONTENT_QUERIES = 16;
 export const DECLARATION_VIEW = 17;
 /** Size of LView's header. Necessary to adjust for it when setting slots.  */
-export const HEADER_OFFSET = 18;
+export const HEADER_OFFSET = 19;
 
 
 // This interface replaces the real LView interface if it is an arg or a
@@ -79,12 +79,13 @@ export interface LView extends Array<any> {
   [FLAGS]: LViewFlags;
 
   /**
-   * The parent view is needed when we exit the view and must restore the previous
-   * `LView`. Without this, the render method would have to keep a stack of
+   * This may store an {@link LView} or {@link LContainer}.
+   *
+   * `LView` - The parent view. This is needed when we exit the view and must restore the previous
+   * LView. Without this, the render method would have to keep a stack of
    * views as it is recursively rendering templates.
    *
-   * This is the "insertion" view for embedded views. This allows us to properly
-   * destroy embedded views.
+   * `LContainer` - The current view is part of a container, and is an embedded view.
    */
   [PARENT]: LView|LContainer|null;
 
@@ -162,6 +163,15 @@ export interface LView extends Array<any> {
   /** An optional custom sanitizer. */
   [SANITIZER]: Sanitizer|null;
 
+  /**
+   * Reference to the first LView or LContainer beneath this LView in
+   * the hierarchy.
+   *
+   * Necessary to store this so views can traverse through their nested views
+   * to remove listeners and call onDestroy callbacks.
+   */
+  [CHILD_HEAD]: LView|LContainer|null;
+
   /**
    * The last LView or LContainer beneath this LView in the hierarchy.
    *
@@ -393,18 +403,6 @@ export interface TView {
    */
   viewQueryStartIndex: number;
 
-  /**
-   * Index of the host node of the first LView or LContainer beneath this LView in
-   * the hierarchy.
-   *
-   * Necessary to store this so views can traverse through their nested views
-   * to remove listeners and call onDestroy callbacks.
-   *
-   * For embedded views, we store the index of an LContainer's host rather than the first
-   * LView to avoid managing splicing when views are added/removed.
-   */
-  childIndex: number;
-
   /**
    * A reference to the first child node located in the view.
    */

packages/core/src/render3/node_manipulation.ts

@@ -369,12 +369,6 @@ export function removeView(lContainer: LContainer, removeIndex: number) {
   destroyLView(view);
 }
 
-/** Gets the child of the given LView */
-export function getLViewChild(lView: LView): LView|LContainer|null {
-  const childIndex = lView[TVIEW].childIndex;
-  return childIndex === -1 ? null : lView[childIndex];
-}
-
 /**
  * A standalone function which destroys an LView,
  * conducting cleanup (e.g. removing listeners, calling onDestroys).

packages/core/src/render3/view_engine_compatibility.ts

@@ -314,7 +314,7 @@ export function createContainerRef(
     hostView[hostTNode.index] = lContainer =
         createLContainer(slotValue, hostView, commentNode, true);
 
-    addToViewTree(hostView, hostTNode.index as number, lContainer);
+    addToViewTree(hostView, lContainer);
   }
 
   return new R3ViewContainerRef(lContainer, hostTNode, hostView);

packages/core/test/bundling/cyclic_import/bundle.golden_symbols.json

@@ -59,6 +59,9 @@
   {
     "name": "INJECTOR_BLOOM_PARENT_SIZE"
   },
+  {
+    "name": "LCONTAINER_LENGTH"
+  },
   {
     "name": "MONKEY_PATCH_KEY_NAME"
   },