Cursor jumps in negative number mask

[Res42]

When programmatically setting the input value and then manually modifying a number input with negative number support, the cursor jumps before the negative sign.

When not setting the input programmatically, it works as expected.

Version info

Angular: 9.1.9
ngx-mask: 9.1.2

Minimal reproduction demo

https://stackblitz.com/edit/ngx-mask-negative-number-cursor-jump-bug

or

HTML:

<form [formGroup]="form">
  <input formControlName="input1" type="text" mask="separator.0" [allowNegativeNumbers]="true"/>
</form>

TypeScript:

form = this.formBuilder.group({
  input1: this.formBuilder.control(42),
})

How to reproduce

1. Set the value of the control programmatically (for example: input1: this.formBuilder.control(42)).
2. Clear the input by hand.
3. Type the negative sign (-).

The cursor will jump to before the negative sign automatically:

This causes that if you write more than one character (-1), then the negative sign will be removed and the value will be 1.

A gif of the bug:

Keys pressed:

1. Mouse left click in the input.
2. Backspace.
3. Backspace.
4. Negative sign (-).
5. 1.

Expected

I don't want the cursor to jump.

Debug

I debugged it a little, but I don't know the library enough to create a PR for this bug.

As I see it, the programmatic value change calls the MaskDirective.writeValue method which sets this._maskService.isNumberValue = true;.
When manually modifying the value, the MaskService._checkSymbols('-') method will try to parse the input as a number (return Number(separatorValue);) which will return NaN, and this somehow causes the cursor jump.

Workaround

If somebody else has this error too, set [dropSpecialCharacters]="false" and parse the string output of ngx-mask yourself.

Duplicate

This issue may be a duplicate of #736.

[vishmay-AF]

Same happens for round braces, after typing when I continuously click the backspace button to erase everything, the symbol on the first location is jumped from backspace.

Regex
(000) 0000 0000

After placing backspace
from '(0|' to '|(' in single backspace.
Here, consider '|' as the cursor

[vishmay-AF]

possible duplicate of #692

[Res42]

I updated my repro to the latest versions (Angular 11, ngx-mask 11.1.4) and I cannot reproduce the problem with these versions.

Closing this issue.