mat-error doesn't show

Bug, feature request, or proposal:

Bug

What is the expected behavior?

mat-error should show

What is the current behavior?

mat-error doesn’t show

What are the steps to reproduce?

 <mat-form-field>
            <input name="address" #address="ngModel" [(ngModel)]="ethernet.address" matInput placeholder="Static IP Address">
            <mat-error *ngIf="!(ethernet.address | ValidateIP)">
              Invalid IP Address
            </mat-error>
 </mat-form-field>

What is the use-case or motivation for changing an existing behavior?

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Is there anything else we should know?

Angular 5.2.9

[kylecordes]

I realize the current behavior is not considered a bug, but I did find it surprisingly inconvenient and unexpected. There are many cases where the user will benefit from seeing a validation error immediately while still typing a value into a field; to do that, following the documentation, I have to write a custom error matcher. Of course this is easy to do, but it also seems like a long way around the block for what could be a trivial switch. So I guess this is also a feature request to improve the developer ergonomics around choosing between different common ways of using a mat-error.

[josephperrott]

Closing as this is working as expected. The mat-error element only becomes visible through the form field control failing validation.