bug(button): FAB buttons cannot be unthemed anymore

[romainmoreau]

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

14

Description

In v15, to put [color]="undefined" on a FAB or mini FAB button doesn't work anymore to get an unthemed FAB or mini FAB button.

Even by providing {} as MAT_FAB_DEFAULT_OPTIONS, the accent color still gets applied by default because of all of the || defaults.color in fab.ts (so removing the 4 of them is a possible solution according to my tests).

Reproduction

https://stackblitz.com/edit/unthemed-fab-buttons-15?file=src/app/app.component.html

Expected Behavior

https://stackblitz.com/edit/unthemed-fab-buttons-14?file=src/app/app.component.html

Actual Behavior

https://stackblitz.com/edit/unthemed-fab-buttons-15?file=src/app/app.component.html

Environment

• Angular: 15.0.2
• CDK/Material: 15.0.1
• Browser(s): Firefox
• Operating System (e.g. Windows, macOS, Ubuntu): Windows

[raphael22]

Reproduce in v16.
I use this behavior to achieve FAB with border instead of plain background btw