refactor(compiler): add AST node for host element

Adds the `HostElement` AST node that can be used to represent the host of a directive. Also exposes the `BindingParser` type so it's easier to pass around the return value of `makeBindingParser`.
angular · crisbeto · Mar 3, 2025 · Mar 4, 2025 · Mar 4, 2025 · Mar 4, 2025
commit 35e460dd2acdb1b103b18d39506bca1bf8ce2ee0
diff --git a/packages/compiler/src/compiler.ts b/packages/compiler/src/compiler.ts
@@ -174,6 +174,7 @@ export {
   UnknownBlock as TmplAstUnknownBlock,
   Variable as TmplAstVariable,
   ViewportDeferredTrigger as TmplAstViewportDeferredTrigger,
+  HostElement as TmplAstHostElement,
   visitAll as tmplAstVisitAll,
   Visitor as TmplAstVisitor,
 } from './render3/r3_ast';
@@ -234,6 +235,10 @@ export {
   parseTemplate,
   ParseTemplateOptions,
 } from './render3/view/template';
+
+// Note: BindingParser is intentionally exported as a type only, because it should
+// be constructed through `makeBindingParser`, rather than its constructor.
+export {type BindingParser} from './template_parser/binding_parser';
 export {createCssSelectorFromNode} from './render3/view/util';
 export * from './resource_loader';
 export * from './schema/dom_element_schema_registry';

diff --git a/packages/compiler/src/render3/r3_ast.ts b/packages/compiler/src/render3/r3_ast.ts
@@ -615,6 +615,27 @@ export class Icu implements Node {
   }
 }
 
+/**
+ * AST node that represents the host element of a directive.
+ * This node is used only for type checking purposes and cannot be produced from a user's template.
+ */
+export class HostElement implements Node {
+  constructor(
+    readonly tagNames: string[],
+    readonly bindings: BoundAttribute[],
+    readonly listeners: BoundEvent[],
+    readonly sourceSpan: ParseSourceSpan,
+  ) {
+    if (tagNames.length === 0) {
+      throw new Error('HostElement must have at least one tag name.');
+    }
+  }
+
+  visit<Result>(): Result {
+    throw new Error(`HostElement cannot be visited`);
+  }
+}
+
 export interface Visitor<Result = any> {
   // Returning a truthy value from `visit()` will prevent `visitAll()` from the call to the typed
   // method and result returned will become the result included in `visitAll()`s result array.