您需要编写自己的验证器函数。

private loginNameValidator = (): ValidatorFn => {
    const userNameValidator = Validators.pattern(USERNAME_REGEX);

    return (control: AbstractControl): ValidationErrors | null => {
        const userNameInvalid = userNameValidator(control);
        if (!userNameInvalid) {
            return null;
        }

        const emailInvalid = Validators.email(control);
        if (!emailInvalid) {
            return null;
        }

        return { loginNameInvalid: true };
    };
};

使用它

this.registerForm = this.formBuilder.group({
    username: ['', [Validators.required, this.loginNameValidator()]],
});

没有满足您需求的内置功能。
您必须为此实现一个自定义验证器。

public userNameOrEmailValidator(): ValidatorFn => {
  return (control: AbstractControl): ValidationErrors | null => {
    const userNameRegex = // TODO: define username regex here.
    const emailRegex = // TODO: define email regex here.
    const isValid = userNameRegex.test(control.value) || emailRegex .test(control.value);
    return !isValid? {inValidUserName: true} : null;
  };
}

可以这样称呼：

this.registerForm = this.formBuilder.group({
    username: ['', [Validators.required, userNameOrEmailValidator()]],
});