fix(ivy): resolve enum values in host bindings (#28523)

Some applications use enum values in their host bindings:

@Component({
  host: {
    '[prop]': EnumType.Key,
  }, ...
})

This commit changes the resolution of host properties to follow the enum
declaration and extract the correct value for the binding.

PR Close #28523

packages/compiler-cli/src/ngtsc/annotations/src/directive.ts

@@ -11,7 +11,7 @@ import * as ts from 'typescript';
 
 import {ErrorCode, FatalDiagnosticError} from '../../diagnostics';
 import {Reference, ResolvedReference} from '../../imports';
-import {PartialEvaluator} from '../../partial_evaluator';
+import {EnumValue, PartialEvaluator} from '../../partial_evaluator';
 import {ClassMember, ClassMemberKind, Decorator, ReflectionHost, filterToMembersWithDecorator, reflectObjectLiteral} from '../../reflection';
 import {AnalysisOutput, CompileResult, DecoratorHandler} from '../../transform';
 
@@ -434,6 +434,11 @@ function extractHostBindings(
           ErrorCode.DECORATOR_ARG_NOT_LITERAL, expr, `Decorator host metadata must be an object`);
     }
     hostMetaMap.forEach((value, key) => {
+      // Resolve Enum references to their declared value.
+      if (value instanceof EnumValue) {
+        value = value.resolved;
+      }
+
       if (typeof value !== 'string' || typeof key !== 'string') {
         throw new Error(`Decorator host metadata must be a string -> string object, got ${value}`);
       }

packages/compiler-cli/test/ngtsc/ngtsc_spec.ts

@@ -1004,6 +1004,31 @@ describe('ngtsc behavioral tests', () => {
     expect(trim(jsContents)).toContain(trim(hostBindingsFn));
   });
 
+  it('should accept enum values as host bindings', () => {
+    env.tsconfig();
+    env.write(`test.ts`, `
+        import {Component, HostBinding, HostListener, TemplateRef} from '@angular/core';
+
+        enum HostBindings {
+          Hello = 'foo'
+        }
+
+        @Component({
+          selector: 'test',
+          template: 'Test',
+          host: {
+            '[attr.hello]': HostBindings.Hello,
+          },
+        })
+        class FooCmp {
+          foo = 'test';
+        }
+    `);
+
+    env.driveMain();
+    expect(env.getContents('test.js')).toContain('"hello", i0.ɵbind(ctx.foo)');
+  });
+
   it('should generate host listeners for directives within hostBindings section', () => {
     env.tsconfig();
     env.write(`test.ts`, `