feat(Core): Add a stub for @visibleForTemplate in angular/src/meta.dart.

This is intended to be a target for later work within the analyzer or linter
package for linting/hinting improper public API usage, as outlined in the
issue: dart-lang/sdk#33353.
PiperOrigin-RevId: 201407857

Author: matanlurey

angular/lib/src/meta.dart

@@ -0,0 +1,60 @@
+// **DO NOT CHANGE**. The analyzer looks for this _specific name_.
+library angular.meta;
+
+// Work in progress.
+//
+// - https://github.com/dart-lang/angular/issues/930
+// - https://github.com/dart-lang/sdk/issues/33353
+//
+// Once this is enabled we will export it from `angular.dart`.
+
+/// Used to annotate a class, field, or method that is public for template use.
+///
+/// An annotated element may be referenced in the _same_ Dart library, or in
+/// any Dart source file whose filename ends in `.template.dart`. Tools, such as
+/// the analyzer can provide feedback if the annotated element is used anywhere
+/// else.
+///
+/// This annotation is intended to be used to identify what elements of a class
+/// or library are only public (not private) because they represent state that
+/// will be referenced in the template HTML of an AngularDart component. For
+/// example:
+///
+/// ```dart
+/// // my_component.dart
+/// import 'package:angular/angular.dart';
+///
+/// @Component(
+///   selector: 'my-comp',
+///   template: 'Hello {{fullName}}!',
+/// )
+/// class MyComponent {
+///   @Input()
+///   String firstName;
+///
+///   @Input()
+///   String lastName;
+///
+///   @visibleForTemplate
+///   String get fullName => '$firstName $lastName';
+/// }
+/// ```
+///
+/// ... `fullName` is a computed field that only exists for use in a `template`
+/// and is not intended to be part of the public API of the component. Another
+/// library attempting to access `fullName` would trigger a diagnostic:
+///
+/// ```dart
+/// // other_lib.dart
+/// import 'my_component.dart';
+///
+/// void example(MyComponent comp) {
+///   // LINT
+///   print(comp.fullName);
+/// }
+/// ```
+const visibleForTemplate = const _VisibleForTemplate();
+
+class _VisibleForTemplate {
+  const _VisibleForTemplate();
+}