refactor(core): introduce API for declaring asynchronous partial meta…

…data (#54908)

Adds the `ɵɵngDeclareClassMetadataAsync` function that will be produced during partial compilation for component classes that have deferred dependencies. At runtime the dependencies will be resolved before setting the metadata.

PR Close #54908

packages/compiler/src/compiler_facade_interface.ts

@@ -230,6 +230,7 @@ export interface R3DeclareComponentFacade extends R3DeclareDirectiveFacade {
   pipes?: {[pipeName: string]: OpaqueValue|(() => OpaqueValue)};
 
 
+  deferBlockDependencies?: (() => Promise<Type>)[];
   viewProviders?: OpaqueValue;
   animations?: OpaqueValue;
   changeDetection?: ChangeDetectionStrategy;

packages/compiler/src/jit_compiler_facade.ts

@@ -183,7 +183,7 @@ export class CompilerFacadeImpl implements CompilerFacade {
     // Parse the template and check for errors.
     const {template, interpolation, defer} = parseJitTemplate(
         facade.template, facade.name, sourceMapUrl, facade.preserveWhitespaces,
-        facade.interpolation);
+        facade.interpolation, undefined);
 
     // Compile the component metadata, including template, into an expression.
     const meta: R3ComponentMetadata<R3TemplateDependency> = {
@@ -442,7 +442,7 @@ function convertDeclareComponentFacadeToMetadata(
     sourceMapUrl: string): R3ComponentMetadata<R3TemplateDependencyMetadata> {
   const {template, interpolation, defer} = parseJitTemplate(
       decl.template, decl.type.name, sourceMapUrl, decl.preserveWhitespaces ?? false,
-      decl.interpolation);
+      decl.interpolation, decl.deferBlockDependencies);
 
   const declarations: R3TemplateDependencyMetadata[] = [];
   if (decl.dependencies) {
@@ -536,7 +536,8 @@ function convertPipeDeclarationToMetadata(pipe: R3DeclarePipeDependencyFacade):
 
 function parseJitTemplate(
     template: string, typeName: string, sourceMapUrl: string, preserveWhitespaces: boolean,
-    interpolation: [string, string]|undefined) {
+    interpolation: [string, string]|undefined,
+    deferBlockDependencies: (() => Promise<unknown>)[]|undefined) {
   const interpolationConfig =
       interpolation ? InterpolationConfig.fromArray(interpolation) : DEFAULT_INTERPOLATION_CONFIG;
   // Parse the template and check for errors.
@@ -551,7 +552,7 @@ function parseJitTemplate(
   return {
     template: parsed,
     interpolation: interpolationConfig,
-    defer: createR3ComponentDeferMetadata(boundTarget)
+    defer: createR3ComponentDeferMetadata(boundTarget, deferBlockDependencies)
   };
 }
 
@@ -622,14 +623,15 @@ function createR3DependencyMetadata(
   return {token, attributeNameType, host, optional, self, skipSelf};
 }
 
-function createR3ComponentDeferMetadata(boundTarget: BoundTarget<any>): R3ComponentDeferMetadata {
+function createR3ComponentDeferMetadata(
+    boundTarget: BoundTarget<any>,
+    deferBlockDependencies: (() => Promise<unknown>)[]|undefined): R3ComponentDeferMetadata {
   const deferredBlocks = boundTarget.getDeferBlocks();
   const blocks = new Map<DeferredBlock, Expression|null>();
 
-  for (const block of deferredBlocks) {
-    // TODO: leaving dependency function empty in JIT mode for now,
-    // to be implemented as one of the next steps.
-    blocks.set(block, null);
+  for (let i = 0; i < deferredBlocks.length; i++) {
+    const dependencyFn = deferBlockDependencies?.[i];
+    blocks.set(deferredBlocks[i], dependencyFn ? new WrappedNodeExpr(dependencyFn) : null);
   }
 
   return {mode: DeferBlockDepsEmitMode.PerBlock, blocks};

packages/compiler/src/render3/partial/api.ts

@@ -190,6 +190,12 @@ export interface R3DeclareComponentMetadata extends R3DeclareDirectiveMetadata {
    */
   dependencies?: R3DeclareTemplateDependencyMetadata[];
 
+  /**
+   * List of defer block dependency functions, ordered by the appearance
+   * of the corresponding deferred block in the template.
+   */
+  deferBlockDependencies?: o.Expression[];
+
   /**
    * A map of pipe names to an expression referencing the pipe type (possibly a forward reference
    * wrapped in a `forwardRef` invocation) which are used in the template.
@@ -557,6 +563,23 @@ export interface R3DeclareClassMetadata extends R3PartialDeclaration {
   propDecorators?: o.Expression;
 }
 
+/**
+ * Describes the shape of the object that the `ɵɵngDeclareClassMetadataAsync()` function accepts.
+ *
+ * This interface serves primarily as documentation, as conformance to this interface is not
+ * enforced during linking.
+ */
+export interface R3DeclareClassMetadataAsync extends R3PartialDeclaration {
+  /** Function that loads the deferred dependencies associated with the component. */
+  resolveDeferredDeps: o.Expression;
+
+  /**
+   * Function that, when invoked with the resolved deferred
+   * dependencies, will return the class metadata.
+   */
+  resolveMetadata: o.Expression;
+}
+
 /**
  * Describes the shape of the object literal that can be
  * passed in as a part of the `hostDirectives` array.

packages/compiler/src/render3/r3_identifiers.ts

@@ -341,6 +341,8 @@ export class Identifiers {
 
   static declareClassMetadata:
       o.ExternalReference = {name: 'ɵɵngDeclareClassMetadata', moduleName: CORE};
+  static declareClassMetadataAsync:
+      o.ExternalReference = {name: 'ɵɵngDeclareClassMetadataAsync', moduleName: CORE};
   static setClassMetadata: o.ExternalReference = {name: 'ɵsetClassMetadata', moduleName: CORE};
   static setClassMetadataAsync:
       o.ExternalReference = {name: 'ɵsetClassMetadataAsync', moduleName: CORE};

packages/core/src/compiler/compiler_facade_interface.ts

@@ -230,6 +230,7 @@ export interface R3DeclareComponentFacade extends R3DeclareDirectiveFacade {
   pipes?: {[pipeName: string]: OpaqueValue|(() => OpaqueValue)};
 
 
+  deferBlockDependencies?: (() => Promise<Type>)[];
   viewProviders?: OpaqueValue;
   animations?: OpaqueValue;
   changeDetection?: ChangeDetectionStrategy;

packages/core/src/core_render3_private_export.ts

@@ -278,6 +278,7 @@ export {
 export {
   FactoryTarget as ɵɵFactoryTarget,
   ɵɵngDeclareClassMetadata,
+  ɵɵngDeclareClassMetadataAsync,
   ɵɵngDeclareComponent,
   ɵɵngDeclareDirective,
   ɵɵngDeclareFactory,

packages/core/src/render3/jit/partial.ts

@@ -8,7 +8,8 @@
 
 import {FactoryTarget, getCompilerFacade, JitCompilerUsage, R3DeclareComponentFacade, R3DeclareDirectiveFacade, R3DeclareFactoryFacade, R3DeclareInjectableFacade, R3DeclareInjectorFacade, R3DeclareNgModuleFacade, R3DeclarePipeFacade} from '../../compiler/compiler_facade';
 import {Type} from '../../interface/type';
-import {setClassMetadata} from '../metadata';
+import {setClassMetadata, setClassMetadataAsync} from '../metadata';
+
 import {angularCoreEnv} from './environment';
 
 /**
@@ -37,6 +38,26 @@ export function ɵɵngDeclareClassMetadata(decl: {
       decl.type, decl.decorators, decl.ctorParameters ?? null, decl.propDecorators ?? null);
 }
 
+/**
+ * Evaluates the class metadata of a component that contains deferred blocks.
+ *
+ * @codeGenApi
+ */
+export function ɵɵngDeclareClassMetadataAsync(decl: {
+  type: Type<any>,
+  resolveDeferredDeps: () => Promise<Type<unknown>>[],
+  resolveMetadata: (...types: Type<unknown>[]) => {
+    decorators: any[];
+    ctorParameters: (() => any[])|null;
+    propDecorators: ({[field: string]: any})|null;
+  },
+}): void {
+  setClassMetadataAsync(decl.type, decl.resolveDeferredDeps, (...types: Type<unknown>[]) => {
+    const meta = decl.resolveMetadata(...types);
+    setClassMetadata(decl.type, meta.decorators, meta.ctorParameters, meta.propDecorators);
+  });
+}
+
 /**
  * Compiles a partial component declaration object into a full component definition object.
  *