Default button styles are broken when there are no editor styles provided

[kjellr]

Describe the bug

When a theme does not provide editor styles, buttons are currently appearing broken in the editor.

To reproduce

1. Use a theme that provides no editor styles (like the Gutenberg Starter theme)
2. Activate Gutenberg 7.9 RC1 (or master currently)
3. Add a button block.
4. View error.

Screenshots

Current, broken example:

Same block, but with the plugin deactivated:

Version

Gutenberg 7.9 RC1

[kjellr]

cc @youknowriad could this be related to #21266?

[paaljoachim]

Testing using the Gutenberg Starter theme: https://github.com/WordPress/gutenberg-starter-theme

Local site using Desktop Server.
Chrome
WordPress 5.4
First I tested with using Gutenberg version 7.8.1.
Button block showed up.

---

Testing Gutenberg version 7.9.0-rc.1.
I am getting the same result as Kjell did further above.

Result:

Selected button:

Selected button block:

Non selected button block:
Does not show button.

[skorasaurus]

can confirm using a build from c3798f1

(also can confirm @carolinan 's issue as well; but I've been experiencing it after rebuilding Gutenberg from master last week; I just thought it was my slower computer ;p)

[carolinan]

I am also experiencing a delay when typing the button text, both with and without editor styles, that does not happen with 7.8.

Win 10, WordPress 5.4, 7.9.0 RC 1, Chrome Version 81.0.4044.92,

[mapk]

I can also confirm this bug using:

Gutenberg 7.8
Twenty Nineteen theme

[jffng]

Looks like if --wp--color-text is not set, the button text fallbacks to white:

gutenberg/packages/block-library/src/button/style.scss

Lines 27 to 32 in c3798f1

	&:hover,
	&:focus,
	&:active,
	&:visited {
	color: var(--wp--color--text, $white);
	}

[youknowriad]

Missed that variable, it should just be removed.