FormControl valueChanges should emit null instead of previous value on control.disabled()

🐞 bug report

Affected Package

The issue is caused by package @angular/forms

Is this a regression?

I don't think so

Description

when a control is disabled it’s new value is null, bit the valueChanges event doesn’t emit with null, but rather with the previous value. This is inconsistent IMHO.

It is specially problematic when using nested forms. My ugly workaround looks like this:

this.editForm.valueChanges.subscribe(value => this.value = this.editForm.disabled ? null : value);

Once this is confirmed as a bug I would really like to contribute with the simple code change and relative tests, please allow me to do so. Thanks 😃

🔬 Minimal Reproduction

https://stackblitz.com/edit/angular-ivy-fjxciy

🌍 Your Environment

Angular Version:

Angular CLI: 9.0.4
Node: 10.16.3
OS: linux x64

Angular: 9.0.4
... animations, cli, common, compiler, compiler-cli, core, forms
... localize, platform-browser, platform-browser-dynamic, router
Ivy Workspace: Yes

Package                      Version
------------------------------------------------------
@angular-devkit/architect    0.900.4
@angular-devkit/core         9.0.4
@angular-devkit/schematics   9.0.4
@angular/cdk                 9.0.1
@ngtools/webpack             9.0.4
@schematics/angular          9.0.4
@schematics/update           0.900.4
rxjs                         6.5.3
typescript                   3.7.5
webpack                      4.41.2

Anything else relevant?

[mlc-mlapis]

Reading this conversation, it reminds me that the base of this is probably the non-existence of readonly property, as it has been since the issue, as #11447, isn’t it?

[yelhouti]

@ameryousuf you can work on this, I am a bit tight on time