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feat(compiler): check that ng-container don't have class bindings #70808

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feat(compiler): check that ng-container don't have class bindings #70808

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5 changes: 5 additions & 0 deletions packages/compiler/src/render3/r3_template_transform.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -242,6 +242,11 @@ class HtmlAstToIvyAst implements html.Visitor {
`Attribute bindings are not supported on ng-container. Use property bindings instead.`,

@mattrbeck mattrbeck Sep 28, 2026

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If a user wrote [attr.class]="foo" today, they'd get an error telling them to use [class]="foo", which would now also error. Maybe we can report these errors in a way that's a little more clear?

bound.sourceSpan,
);
} else if (
bound.type === BindingType.Class ||
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(bound.type === BindingType.Property && bound.name === 'class')

@mattrbeck mattrbeck Sep 28, 2026

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Would this be breaking if a directive has a "class" input today?

@mattrbeck mattrbeck Sep 28, 2026

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Should we also check if bound.name === 'style'?

) {
this.reportError(`Class bindings are not supported on ng-container.`, bound.sourceSpan);
}
}
}
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20 changes: 20 additions & 0 deletions packages/compiler/test/render3/r3_template_transform_spec.ts
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Expand Up @@ -3055,12 +3055,32 @@ describe('R3 template transform', () => {
);
});

it('should report an error for class bindings on ng-container', () => {
const template = `<ng-container [class.foo]="true"></ng-container>`;
const errors = parse(template, {ignoreError: true}).errors;
expect(errors.length).toBe(1);
expect(errors[0].msg).toBe('Class bindings are not supported on ng-container.');
});
it('should report an error for [class] property bindings on ng-container', () => {
const template = `<ng-container [class]="'my-class'"></ng-container>`;
const errors = parse(template, {ignoreError: true}).errors;
expect(errors.length).toBe(1);
expect(errors[0].msg).toBe('Class bindings are not supported on ng-container.');
});

it('should not report an error on non-attr bindings on ng-container', () => {
const template = `<ng-container *ngIf"test" [ngTemplateOutlet]="foo"></ng-container>`;
const errors = parse(template, {ignoreError: true}).errors;
expect(errors.length).toBe(0);
});

it('should report an error for class interpolation on ng-container', () => {
const template = `<ng-container class="{{foo}}"></ng-container>`;
const errors = parse(template, {ignoreError: true}).errors;
expect(errors.length).toBe(1);
expect(errors[0].msg).toBe('Class bindings are not supported on ng-container.');
});

describe('@content blocks', () => {
it('should parse a valid @content block', () => {
expectFromHtml(`
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7 changes: 3 additions & 4 deletions packages/core/test/acceptance/host_binding_spec.ts
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Expand Up @@ -682,7 +682,7 @@ describe('host bindings', () => {
expect(childElement.style.opacity).toEqual('0.5');
});

it('should allow class-bindings to be placed on ng-container elements', () => {
it('should NOT allow class-bindings to be placed on ng-container elements', () => {
@Component({
template: `
<ng-container [class.foo]="true" dir-that-adds-other-classes>...</ng-container>
Expand All @@ -703,9 +703,8 @@ describe('host bindings', () => {

TestBed.configureTestingModule({declarations: [MyApp, DirThatAddsOtherClasses]});
expect(() => {
const fixture = TestBed.createComponent(MyApp);
fixture.detectChanges();
}).not.toThrow();
TestBed.createComponent(MyApp);
}).toThrowError(/Class bindings are not supported on ng-container/);
});
});

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