bug(theming): [v20.0.1] brand-family not being set along plain-family when using a single font-family value for mat.theme typography (uses default Roboto)

[anisabboud]

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

19.2.17

Description

If you define a mat.theme with a single value for typography, the font is not applying to some headings such as dialog-title. They are using the default Roboto font.

I believe the bug is in line 117 in _m3-system.scss.
If $typography is not a map (@else clause), then only $plain: $typography; is being set, while $brand remains $plain; from line 106, which is (Roboto, sans-serif) (from line 105).

components/src/material/core/tokens/_m3-system.scss

Lines 104 to 118 in 020c6af

	@if ($typography) {
	$plain: (Roboto, sans-serif);
	$brand: $plain;
	$bold: 700;
	$medium: 500;
	$regular: 400;
	@if (meta.type-of($typography) == map) {
	$plain: map.get($typography, plain-family);
	$brand: map.get($typography, brand-family) or $plain;
	$bold: map.get($typography, bold-weight) or $bold;
	$medium: map.get($typography, medium-weight) or $medium;
	$regular: map.get($typography, regular-weight) or $regular;
	} @else {
	$plain: $typography;
	}

Reproduction

Steps to reproduce: Define a mat.theme with a single value for typography:

html {
  color-scheme: light;
  @include mat.theme((
    color: $primary-palette,
    typography: $my-font,  // Should apply to both `plain-family` and `brand-family`, but it's not applying to `brand-family`.
    density: 0,
  ));
}

Expected Behavior

https://material.angular.dev/guide/theming#single-font-family-value

If you provide a font family, Angular Material uses it for all the text in its components.

Actual Behavior

The single provided font-family is being applied to all components, but not to some headers like dialog-title,

Environment

• Angular: 20.0.0
• CDK/Material: 20.0.1
• Browser(s): Chrome