feat(core): enable the new directive composition API (#47642)

Enables the new directive composition API by exposing the `hostDirectives` property on the `Directive` and `Component` decorators. Also cleans up some casts that were put in place while the feature was being developed.

Fixes #8785.

PR Close #47642

goldens/public-api/core/index.md

@@ -439,6 +439,11 @@ export interface Directive {
     host?: {
         [key: string]: string;
     };
+    hostDirectives?: (Type<unknown> | {
+        directive: Type<unknown>;
+        inputs?: string[];
+        outputs?: string[];
+    })[];
     inputs?: string[];
     jit?: true;
     outputs?: string[];

packages/core/src/metadata/directives.ts

@@ -332,6 +332,17 @@ export interface Directive {
    * @developerPreview
    */
   standalone?: boolean;
+
+  /**
+   * Standalone directives that should be applied to the host whenever the directive is matched.
+   * By default none of the inputs or outputs of the host directives will be available on the host,
+   * unless they are specified in the `inputs` or `outputs` properties.
+   */
+  hostDirectives?: (Type<unknown>|{
+    directive: Type<unknown>,
+    inputs?: string[],
+    outputs?: string[],
+  })[];
 }
 
 /**

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

@@ -416,12 +416,8 @@ export function directiveMetadata(type: Type<any>, metadata: Directive): R3Direc
     providers: metadata.providers || null,
     viewQueries: extractQueriesMetadata(type, propMetadata, isViewQuery),
     isStandalone: !!metadata.standalone,
-    hostDirectives:
-        // TODO(crisbeto): remove the `as any` usage here and down in the `map` call once
-        // host directives are exposed in the public API.
-        (metadata as any)
-            .hostDirectives?.map(
-                (directive: any) => typeof directive === 'function' ? {directive} : directive) ||
+    hostDirectives: metadata.hostDirectives?.map(
+                        directive => typeof directive === 'function' ? {directive} : directive) ||
         null
   };
 }