Required Input() parameters #18156
Description
I'm submitting a...
[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report
[x] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question
Current behavior
Regardless of whether Input parameters of a component are optional or not, AoT does not throw an error or warning, making it difficult to find out mistakes where a required attribute is not passed down to a component in the template before runtime.
@Component({
selector: 'app-username',
template: `
<p>{{username}}</p>
`,
})
export class UsernameCompoennt implements OnInit {
@Input() id: string;
username: string;
constructor(private usernameService: UsernameService) { }
ngOnInit() {
this.usernameService.getUsername(id).subscribe(user => this.username = user.name);
}
};
<app-name></app-name>
// will be compiled with no warning or error, while the component is essentially useless without name being provided
Expected behavior
AoT will throw a warning or error, because a required input parameter has not been passed down to the component
Minimal reproduction of the problem with instructions
What is the motivation / use case for changing the behavior?
Will enable catching errors during compilation
Environment
Angular version: 4.2.X