refactor(core): change `getPreviousOrParentTNode` to return `TNode|null` (#38707)

This change makes `getPreviousOrParentTNode` return `TNode|null` (rather
than just `TNode`) which is more reflective of the reality. The
`getPreviousOrParentTNode` can be `null` upon entering the `LView`.

PR Close #38707

packages/core/src/render3/component.ts

@@ -229,7 +229,7 @@ export function createRootComponent<T>(
     componentDef.contentQueries(RenderFlags.Create, component, rootLView.length - 1);
   }
 
-  const rootTNode = getPreviousOrParentTNode();
+  const rootTNode = getPreviousOrParentTNode()!;
   if (tView.firstCreatePass &&
       (componentDef.hostBindings !== null || componentDef.hostAttrs !== null)) {
     const elementIndex = rootTNode.index - HEADER_OFFSET;

packages/core/src/render3/di_setup.ts

@@ -76,7 +76,7 @@ function resolveProvider(
     let token: any = isTypeProvider(provider) ? provider : resolveForwardRef(provider.provide);
     let providerFactory: () => any = providerToFactory(provider);
 
-    const tNode = getPreviousOrParentTNode();
+    const tNode = getPreviousOrParentTNode()!;
     const beginIndex = tNode.providerIndexes & TNodeProviderIndexes.ProvidersStartIndexMask;
     const endIndex = tNode.directiveStart;
     const cptViewProvidersCount =

packages/core/src/render3/i18n/i18n_parse.ts

@@ -70,7 +70,7 @@ export function i18nStartFirstPass(
     lView: LView, tView: TView, index: number, message: string, subTemplateIndex?: number) {
   const startIndex = tView.blueprint.length - HEADER_OFFSET;
   i18nVarsCount = 0;
-  const previousOrParentTNode = getPreviousOrParentTNode();
+  const previousOrParentTNode = getPreviousOrParentTNode()!;
   const parentTNode =
       getIsParent() ? previousOrParentTNode : previousOrParentTNode && previousOrParentTNode.parent;
   let parentIndex =
@@ -212,7 +212,7 @@ export function i18nStartFirstPass(
  */
 export function i18nAttributesFirstPass(
     lView: LView, tView: TView, index: number, values: string[]) {
-  const previousElement = getPreviousOrParentTNode();
+  const previousElement = getPreviousOrParentTNode()!;
   const previousElementIndex = previousElement.index - HEADER_OFFSET;
   const updateOpCodes: I18nUpdateOpCodes = [];
   if (ngDevMode) {

packages/core/src/render3/instructions/di.ts

@@ -59,7 +59,7 @@ export function ɵɵdirectiveInject<T>(
  * @codeGenApi
  */
 export function ɵɵinjectAttribute(attrNameToInject: string): string|null {
-  return injectAttributeImpl(getPreviousOrParentTNode(), attrNameToInject);
+  return injectAttributeImpl(getPreviousOrParentTNode()!, attrNameToInject);
 }
 
 /**

packages/core/src/render3/instructions/element.ts

@@ -128,7 +128,7 @@ export function ɵɵelementStart(
  * @codeGenApi
  */
 export function ɵɵelementEnd(): void {
-  let previousOrParentTNode = getPreviousOrParentTNode();
+  let previousOrParentTNode = getPreviousOrParentTNode()!;
   ngDevMode && assertDefined(previousOrParentTNode, 'No parent node to close.');
   if (getIsParent()) {
     setIsNotParent();

packages/core/src/render3/instructions/element_container.ts

@@ -98,7 +98,7 @@ export function ɵɵelementContainerStart(
  * @codeGenApi
  */
 export function ɵɵelementContainerEnd(): void {
-  let previousOrParentTNode = getPreviousOrParentTNode();
+  let previousOrParentTNode = getPreviousOrParentTNode()!;
   const tView = getTView();
   if (getIsParent()) {
     setIsNotParent();

packages/core/src/render3/instructions/listener.ts

@@ -41,7 +41,7 @@ export function ɵɵlistener(
     eventTargetResolver?: GlobalTargetResolver): typeof ɵɵlistener {
   const lView = getLView();
   const tView = getTView();
-  const tNode = getPreviousOrParentTNode();
+  const tNode = getPreviousOrParentTNode()!;
   listenerInternal(
       tView, lView, lView[RENDERER], tNode, eventName, listenerFn, useCapture, eventTargetResolver);
   return ɵɵlistener;
@@ -71,7 +71,7 @@ export function ɵɵlistener(
 export function ɵɵsyntheticHostListener(
     eventName: string, listenerFn: (e?: any) => any, useCapture = false,
     eventTargetResolver?: GlobalTargetResolver): typeof ɵɵsyntheticHostListener {
-  const tNode = getPreviousOrParentTNode();
+  const tNode = getPreviousOrParentTNode()!;
   const lView = getLView();
   const tView = getTView();
   const currentDef = getCurrentDirectiveDef(tView.data);

packages/core/src/render3/instructions/shared.ts

@@ -1125,7 +1125,7 @@ function logUnknownPropertyError(propName: string, tNode: TNode): void {
  * Instantiate a root component.
  */
 export function instantiateRootComponent<T>(tView: TView, lView: LView, def: ComponentDef<T>): T {
-  const rootTNode = getPreviousOrParentTNode();
+  const rootTNode = getPreviousOrParentTNode()!;
   if (tView.firstCreatePass) {
     if (def.providersResolver) def.providersResolver(def);
     generateExpandoInstructionBlock(tView, rootTNode, 1);

packages/core/src/render3/query.ts

@@ -504,7 +504,7 @@ export function ɵɵcontentQuery<T>(
     directiveIndex: number, predicate: Type<any>|InjectionToken<unknown>|string[], descend: boolean,
     read?: any): void {
   contentQueryInternal(
-      getTView(), getLView(), predicate, descend, read, false, getPreviousOrParentTNode(),
+      getTView(), getLView(), predicate, descend, read, false, getPreviousOrParentTNode()!,
       directiveIndex);
 }
 
@@ -524,7 +524,7 @@ export function ɵɵstaticContentQuery<T>(
     directiveIndex: number, predicate: Type<any>|InjectionToken<unknown>|string[], descend: boolean,
     read?: any): void {
   contentQueryInternal(
-      getTView(), getLView(), predicate, descend, read, true, getPreviousOrParentTNode(),
+      getTView(), getLView(), predicate, descend, read, true, getPreviousOrParentTNode()!,
       directiveIndex);
 }
 

packages/core/src/render3/state.ts

@@ -54,8 +54,7 @@ interface LFrame {
    *
    * This is used in conjunction with `isParent`.
    */
-  // FIXME(misko): should be `TNode|null` (add comment explaining it.)
-  previousOrParentTNode: TNode;
+  previousOrParentTNode: TNode|null;
 
   /**
    * If `isParent` is:
@@ -263,7 +262,7 @@ export function ɵɵrestoreView(viewToRestore: OpaqueViewState) {
   instructionState.lFrame.contextLView = viewToRestore as any as LView;
 }
 
-export function getPreviousOrParentTNode(): TNode {
+export function getPreviousOrParentTNode(): TNode|null {
   return instructionState.lFrame.previousOrParentTNode;
 }
 
@@ -441,7 +440,7 @@ function allocLFrame() {
 
 function createLFrame(parent: LFrame|null): LFrame {
   const lFrame: LFrame = {
-    previousOrParentTNode: null!,  //
+    previousOrParentTNode: null,  //
     isParent: true,               //
     lView: null!,                 //
     tView: null!,                 //

packages/core/src/render3/view_engine_compatibility.ts

@@ -43,7 +43,7 @@ import { ViewRef } from './view_ref';
  */
 export function injectElementRef(ElementRefToken: typeof ViewEngine_ElementRef):
     ViewEngine_ElementRef {
-  return createElementRef(ElementRefToken, getPreviousOrParentTNode(), getLView());
+  return createElementRef(ElementRefToken, getPreviousOrParentTNode()!, getLView());
 }
 
 let R3ElementRef: {new (native: RElement|RComment): ViewEngine_ElementRef};
@@ -79,7 +79,7 @@ export function injectTemplateRef<T>(
     TemplateRefToken: typeof ViewEngine_TemplateRef,
     ElementRefToken: typeof ViewEngine_ElementRef): ViewEngine_TemplateRef<T>|null {
   return createTemplateRef<T>(
-      TemplateRefToken, ElementRefToken, getPreviousOrParentTNode(), getLView());
+      TemplateRefToken, ElementRefToken, getPreviousOrParentTNode()!, getLView());
 }
 
 /**
@@ -407,7 +407,7 @@ export function createContainerRef(
 
 /** Returns a ChangeDetectorRef (a.k.a. a ViewRef) */
 export function injectChangeDetectorRef(isPipe = false): ViewEngine_ChangeDetectorRef {
-  return createViewRef(getPreviousOrParentTNode(), getLView(), isPipe);
+  return createViewRef(getPreviousOrParentTNode()!, getLView(), isPipe);
 }
 
 /**
@@ -453,7 +453,7 @@ export function injectRenderer2(): Renderer2 {
   // We need the Renderer to be based on the component that it's being injected into, however since
   // DI happens before we've entered its view, `getLView` will return the parent view instead.
   const lView = getLView();
-  const tNode = getPreviousOrParentTNode();
+  const tNode = getPreviousOrParentTNode()!;
   const nodeAtIndex = getComponentLViewByIndex(tNode.index, lView);
   return getOrCreateRenderer2(isLView(nodeAtIndex) ? nodeAtIndex : lView);
 }