clients/angular/src/pipes/user-name.pipe.ts

import {
    Pipe,
    PipeTransform,
} from '@angular/core';

interface User {
    name?: string;
    email: string;
}

@Pipe({
    name: 'userName',
})
export class UserNamePipe implements PipeTransform {
    transform(user?: User): string {
        if (user == null) {
            return null;
        }

        return user.name == null || user.name.trim() === '' ? user.email : user.name;
    }
}