Angular component naming limitations - 'select

In Angular 6 (6.0.7) I'm trying to generate a component via the CLI. I type in ng g c t1-2-3-user and get the error message Selector (app-t1-2-3-user) is invalid.

Is there something inherently not allowed in this name? I've already created a parent module called t1-myModule via ng g module t1-myModule and it was created successfully. Within that module is where I'm trying to generate this component.

I've tried creating a different name like ng g c t1-testComponent and it works fine - so the CLI doesn't appear to be broken. Something about naming a component t1-2-3-user in my setup is not liked by Angular.

EDIT: after further testing, it appears Angular doesn't like the first character after a dash - to be a number. Possibly a similar limitation as in JavaScript variables. I assume since it gets compiled into JavaScript? Can anyone elaborate on/confirm this component naming constraint?

As per W3C standards selector should qualify below set of things

In CSS, identifiers (including element names, classes, and IDs in selectors) can contain

only the characters [a-zA-Z0-9] and ISO 10646 characters U+00A0 and higher, plus the hyphen (-) and the underscore (_);

they cannot start with a digit, two hyphens, or a hyphen followed by a digit

Identifiers can also contain escaped characters and any ISO 10646 character as a numeric code (see next item). For instance, the identifier "B&W?" may be written as "B\&W\?" or "B\26 W\3F".

So Angular is following the W3C convention for selector name. I was expected to see similar thing baked in inside code somewhere. After digging into CLI code It turns out that angular uses regex (/^[a-zA-Z][.0-9a-zA-Z]*(:?-[a-zA-Z][.0-9a-zA-Z]*)*$/) to validate selector name before creating files.

So while running ng generate component component-name command it calls @angular/schematics for component command and pass the component name parameter to it. While executing command with set of instruction it fires below line to validate selector.

validateHtmlSelector(options.selector);

validation.ts

export const htmlSelectorRe = /^[a-zA-Z][.0-9a-zA-Z]*(:?-[a-zA-Z][.0-9a-zA-Z]*)*$/;
export function validateHtmlSelector(selector: string): void {
  if (selector && !htmlSelectorRe.test(selector)) {
    throw new SchematicsException(tags.oneLine`Selector (${selector})
        is invalid.`);
  }
}