fix(mat-input): matInput with type number fires twice changeValue event inside formGroup

[gogakoreli]

Bug, feature request, or proposal:

Bug

What is the expected behavior?

matInput with type="number" shouldn't fire valueChanges event twice, when inside ReactiveForm

What is the current behavior?

matInput with type="number" fires valueChanges event twice, when inside ReactiveForm

What are the steps to reproduce?

https://stackblitz.com/edit/type-number-input-2-value-changes-fired

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

Event shouldn't fire twice it is extra and bad performance wise

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

5.2.2

Is there anything else we should know?

Open console inside developer tools and look at console when changing value of Age inside my StackBlitz example. You can see that when you change value of age event is fired once and then when you move your focus on other component it fires second same event again.

[julianobrasil]

It seems that angular (not material) is just forwarding the standard html behavior: emitting a change event on keydown and when the element loses focus.

[gogakoreli]

I thought same but I don't understand why doesn't same happen on other input elements?

[mmalerba]

Here is the same example with all Angular Material stuff removed as proof that it is not a Material issue: https://stackblitz.com/edit/type-number-input-2-value-changes-fired-o6m19b?file=main.ts

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