feat(ivy): accept multiple values for exportAs in the compiler (#28001)

exportAs in @Directive metadata supports multiple values, separated by
commas. Previously it was treated as a single value string.

This commit modifies the compiler to understand that exportAs is a
string[]. It stops short of carrying the multiple values through to the
runtime. Instead, it only emits the first one. A future commit will modify
the runtime to accept all the values.

PR Close #28001

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

@@ -60,7 +60,7 @@ export const enum DirectiveDefFlags {ContentQuery = 0b10}
 export interface PipeType<T> extends Type<T> { ngPipeDef: never; }
 
 export type DirectiveDefWithMeta<
-    T, Selector extends string, ExportAs extends string, InputMap extends{[key: string]: string},
+    T, Selector extends string, ExportAs extends string[], InputMap extends{[key: string]: string},
     OutputMap extends{[key: string]: string}, QueryFields extends string[]> = DirectiveDef<T>;
 
 /**
@@ -163,7 +163,7 @@ export interface DirectiveDef<T> extends BaseDef<T> {
 }
 
 export type ComponentDefWithMeta<
-    T, Selector extends String, ExportAs extends string, InputMap extends{[key: string]: string},
+    T, Selector extends String, ExportAs extends string[], InputMap extends{[key: string]: string},
     OutputMap extends{[key: string]: string}, QueryFields extends string[]> = ComponentDef<T>;
 
 /**

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

@@ -119,7 +119,7 @@ export interface R3DirectiveMetadataFacade {
   inputs: string[];
   outputs: string[];
   usesInheritance: boolean;
-  exportAs: string|null;
+  exportAs: string[]|null;
   providers: Provider[]|null;
 }
 

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

@@ -150,7 +150,7 @@ function directiveMetadata(type: Type<any>, metadata: Directive): R3DirectiveMet
     },
     typeSourceSpan: null !,
     usesInheritance: !extendsDirectlyFromObject(type),
-    exportAs: metadata.exportAs || null,
+    exportAs: extractExportAs(metadata.exportAs),
     providers: metadata.providers || null,
   };
 }
@@ -189,6 +189,14 @@ function extractQueriesMetadata(
   return queriesMeta;
 }
 
+function extractExportAs(exportAs: string | undefined): string[]|null {
+  if (exportAs === undefined) {
+    return null;
+  }
+
+  return exportAs.split(',').map(part => part.trim());
+}
+
 function isContentQuery(value: any): value is Query {
   const name = value.ngMetadataName;
   return name === 'ContentChild' || name === 'ContentChildren';