fix(compiler): recover event parse when animation event name is empty (#39925)

Now when the animation trigger output event is missing its phase value name, the `BoundEvent` will be ignored,
but it's useful for completion in language service.

PR Close #39925

packages/compiler/src/template_parser/binding_parser.ts

@@ -443,21 +443,19 @@ export class BindingParser {
     const matches = splitAtPeriod(name, [name, '']);
     const eventName = matches[0];
     const phase = matches[1].toLowerCase();
-    if (phase) {
-      switch (phase) {
-        case 'start':
-        case 'done':
     const ast = this._parseAction(expression, handlerSpan);
     targetEvents.push(new ParsedEvent(
         eventName, phase, ParsedEventType.Animation, ast, sourceSpan, handlerSpan, keySpan));
-          break;
 
-        default:
+    if (eventName.length === 0) {
+      this._reportError(`Animation event name is missing in binding`, sourceSpan);
+    }
+    if (phase) {
+      if (phase !== 'start' && phase !== 'done') {
         this._reportError(
             `The provided animation output phase value "${phase}" for "@${
                 eventName}" is not supported (use start or done)`,
             sourceSpan);
-          break;
       }
     } else {
       this._reportError(

packages/compiler/test/render3/r3_template_transform_spec.ts

@@ -92,8 +92,8 @@ class R3AstHumanizer implements t.Visitor<void> {
   }
 }
 
-function expectFromHtml(html: string) {
-  const res = parse(html);
+function expectFromHtml(html: string, ignoreError = false) {
+  const res = parse(html, {ignoreError});
   return expectFromR3Nodes(res.nodes);
 }
 
@@ -399,6 +399,27 @@ describe('R3 template transform', () => {
       expect(() => parse('<div (event)="">')).toThrowError(/Empty expressions are not allowed/);
       expect(() => parse('<div (event)="   ">')).toThrowError(/Empty expressions are not allowed/);
     });
+
+    it('should parse bound animation events when event name is empty', () => {
+      expectFromHtml('<div (@)="onAnimationEvent($event)"></div>', true).toEqual([
+        ['Element', 'div'],
+        ['BoundEvent', '', null, 'onAnimationEvent($event)'],
+      ]);
+      expect(() => parse('<div (@)></div>'))
+          .toThrowError(/Animation event name is missing in binding/);
+    });
+
+    it('should report invalid phase value of animation event', () => {
+      expect(() => parse('<div (@event.invalidPhase)></div>'))
+          .toThrowError(
+              /The provided animation output phase value "invalidphase" for "@event" is not supported \(use start or done\)/);
+      expect(() => parse('<div (@event.)></div>'))
+          .toThrowError(
+              /The animation trigger output event \(@event\) is missing its phase value name \(start or done are currently supported\)/);
+      expect(() => parse('<div (@event)></div>'))
+          .toThrowError(
+              /The animation trigger output event \(@event\) is missing its phase value name \(start or done are currently supported\)/);
+    });
   });
 
   describe('variables', () => {

packages/compiler/test/render3/view/util.ts

@@ -78,15 +78,17 @@ export function toStringExpression(expr: e.AST): string {
 
 // Parse an html string to IVY specific info
 export function parseR3(
-    input: string, options: {preserveWhitespaces?: boolean, leadingTriviaChars?: string[]} = {}):
-    Render3ParseResult {
+    input: string,
+    options: {preserveWhitespaces?: boolean,
+              leadingTriviaChars?: string[],
+              ignoreError?: boolean} = {}): Render3ParseResult {
   const htmlParser = new HtmlParser();
 
   const parseResult = htmlParser.parse(
       input, 'path:://to/template',
       {tokenizeExpansionForms: true, leadingTriviaChars: options.leadingTriviaChars});
 
-  if (parseResult.errors.length > 0) {
+  if (parseResult.errors.length > 0 && !options.ignoreError) {
     const msg = parseResult.errors.map(e => e.toString()).join('\n');
     throw new Error(msg);
   }
@@ -105,7 +107,7 @@ export function parseR3(
       new BindingParser(expressionParser, DEFAULT_INTERPOLATION_CONFIG, schemaRegistry, null, []);
   const r3Result = htmlAstToRender3Ast(htmlNodes, bindingParser);
 
-  if (r3Result.errors.length > 0) {
+  if (r3Result.errors.length > 0 && !options.ignoreError) {
     const msg = r3Result.errors.map(e => e.toString()).join('\n');
     throw new Error(msg);
   }