refactor(material/expansion): switch to tokens API (#27390)

Reworks the expansion panel to use the tokens theming API.

Author: crisbeto

src/material/core/tokens/_token-utils.scss

@@ -39,6 +39,7 @@ $placeholder-typography-config: (
   caption: $_placeholder-typography-level-config,
   button: $_placeholder-typography-level-config,
   overline: $_placeholder-typography-level-config,
+  subheading-1: $_placeholder-typography-level-config,
 );
 
 // Placeholder density config that can be passed to token getter functions when generating token

src/material/core/tokens/m2/mat/_expansion.scss

@@ -0,0 +1,90 @@
+@use 'sass:map';
+@use '../../token-utils';
+@use '../../../theming/theming';
+@use '../../../style/sass-utils';
+@use '../../../typography/typography-utils';
+
+// The prefix used to generate the fully qualified name for tokens in this file.
+$prefix: (mat, expansion);
+
+// Tokens that can't be configured through Angular Material's current theming API,
+// but may be in a future version of the theming API.
+@function get-unthemable-tokens() {
+  @return (
+    container-shape: 4px,
+  );
+}
+
+// Tokens that can be configured through Angular Material's color theming API.
+@function get-color-tokens($config) {
+  $foreground: map.get($config, foreground);
+  $background: map.get($config, background);
+
+  @return (
+    container-background-color: theming.get-color-from-palette($background, card),
+    container-text-color: theming.get-color-from-palette($foreground, text),
+    actions-divider-color: theming.get-color-from-palette($foreground, divider),
+    header-hover-state-layer-color: theming.get-color-from-palette($background, hover),
+    header-focus-state-layer-color: theming.get-color-from-palette($background, hover),
+    header-disabled-state-text-color: theming.get-color-from-palette($foreground, disabled-button),
+    header-text-color: theming.get-color-from-palette($foreground, text),
+    header-description-color: theming.get-color-from-palette($foreground, secondary-text),
+    header-indicator-color: theming.get-color-from-palette($foreground, secondary-text),
+  );
+}
+
+// Tokens that can be configured through Angular Material's typography theming API.
+@function get-typography-tokens($config) {
+  $fallback-font-family: typography-utils.font-family($config);
+
+  @return (
+    header-text-font: typography-utils.font-family($config, subheading-1) or $fallback-font-family,
+    header-text-size: typography-utils.font-size($config, subheading-1),
+    header-text-weight: typography-utils.font-weight($config, subheading-1),
+
+    // TODO(crisbeto): these two properties weren't set at all before the introduction of tokens,
+    // but it's inconsistent not to provide them since the container sets all of them. Eventually
+    // we should change the values to use come from `subheading-1`.
+    header-text-line-height: inherit,
+    header-text-tracking: inherit,
+
+    container-text-font: typography-utils.font-family($config, body-1) or $fallback-font-family,
+    container-text-line-height: typography-utils.line-height($config, body-1),
+    container-text-size: typography-utils.font-size($config, body-1),
+    container-text-tracking: typography-utils.letter-spacing($config, body-1),
+    container-text-weight: typography-utils.font-weight($config, body-1),
+  );
+}
+
+// Tokens that can be configured through Angular Material's density theming API.
+@function get-density-tokens($config) {
+  $scale: theming.clamp-density($config, -3);
+  $collapsed-scale: (
+    0: 48px,
+    -1: 44px,
+    -2: 40px,
+    -3: 36px,
+  );
+  $expanded-scale: (
+    0: 64px,
+    -1: 60px,
+    -2: 56px,
+    -3: 48px,
+  );
+
+  @return (
+    header-collapsed-state-height: map.get($collapsed-scale, $scale),
+    header-expanded-state-height: map.get($expanded-scale, $scale),
+  );
+}
+
+// Combines the tokens generated by the above functions into a single map with placeholder values.
+// This is used to create token slots.
+@function get-token-slots() {
+  @return sass-utils.deep-merge-all(
+      get-unthemable-tokens(),
+      get-color-tokens(token-utils.$placeholder-color-config),
+      get-typography-tokens(token-utils.$placeholder-typography-config),
+      get-density-tokens(token-utils.$placeholder-density-config)
+  );
+}

src/material/expansion/_expansion-legacy-index.scss

@@ -1,3 +1,2 @@
 @forward 'expansion-variables' as mat-expansion-panel-*;
-@forward 'expansion-mixins' as mat-*;
 @forward 'expansion-theme' as mat-expansion-panel-*;

src/material/expansion/_expansion-mixins.import.scss

@@ -2,7 +2,6 @@
 @forward '../core/style/private.import';
 @forward 'expansion-variables' as mat-expansion-panel-*;
 @forward '../core/typography/typography-utils.import';
-@forward 'expansion-mixins' as mat-*;
 @forward 'expansion-theme' as mat-expansion-panel-*;
 
 @import '../core/density/private/compatibility';
@@ -11,4 +10,3 @@
 @import '../core/style/private';
 @import '../core/typography/typography-utils';
 @import './expansion-variables';
-@import './expansion-mixins';

src/material/expansion/_expansion-mixins.scss

@@ -1,90 +1,34 @@
-@use 'sass:map';
-@use '../core/density/private/compatibility';
 @use '../core/theming/theming';
-@use '../core/style/private';
 @use '../core/typography/typography';
-@use '../core/typography/typography-utils';
-@use './expansion-variables';
-@use './expansion-mixins';
+@use '../core/style/sass-utils';
+@use '../core/tokens/token-utils';
+@use '../core/tokens/m2/mat/expansion' as tokens-mat-expansion;
 
 @mixin color($config-or-theme) {
   $config: theming.get-color-config($config-or-theme);
-  $background: map.get($config, background);
-  $foreground: map.get($config, foreground);
 
-  .mat-expansion-panel {
-    @include private.private-theme-overridable-elevation(2, $config);
-    background: theming.get-color-from-palette($background, card);
-    color: theming.get-color-from-palette($foreground, text);
-  }
-
-  .mat-action-row {
-    border-top-color: theming.get-color-from-palette($foreground, divider);
-  }
-
-  @include expansion-mixins.private-expansion-focus {
-    background: theming.get-color-from-palette($background, hover);
-  }
-
-  // Disable the hover on touch devices since it can appear like it is stuck. We can't use
-  // `@media (hover)` above, because the desktop support browser support isn't great.
-  @media (hover: none) {
-    .mat-expansion-panel:not(.mat-expanded):not([aria-disabled='true'])
-      .mat-expansion-panel-header:hover {
-      background: theming.get-color-from-palette($background, card);
-    }
-  }
-
-  .mat-expansion-panel-header-title {
-    color: theming.get-color-from-palette($foreground, text);
-  }
-
-  .mat-expansion-panel-header-description,
-  .mat-expansion-indicator::after {
-    color: theming.get-color-from-palette($foreground, secondary-text);
-  }
-
-  .mat-expansion-panel-header[aria-disabled='true'] {
-    color: theming.get-color-from-palette($foreground, disabled-button);
-
-    .mat-expansion-panel-header-title,
-    .mat-expansion-panel-header-description {
-      color: inherit;
-    }
+  @include sass-utils.current-selector-or-root() {
+    @include token-utils.create-token-values(tokens-mat-expansion.$prefix,
+      tokens-mat-expansion.get-color-tokens($config));
   }
 }
 
 @mixin typography($config-or-theme) {
   $config: typography.private-typography-to-2014-config(
       theming.get-typography-config($config-or-theme));
-  .mat-expansion-panel-header {
-    font: {
-      family: typography-utils.font-family($config, subheading-1);
-      size: typography-utils.font-size($config, subheading-1);
-      weight: typography-utils.font-weight($config, subheading-1);
-    }
-  }
 
-  .mat-expansion-panel-content {
-    @include typography-utils.typography-level($config, body-1);
+  @include sass-utils.current-selector-or-root() {
+    @include token-utils.create-token-values(tokens-mat-expansion.$prefix,
+      tokens-mat-expansion.get-typography-tokens($config));
   }
 }
 
 @mixin density($config-or-theme) {
   $density-scale: theming.get-density-config($config-or-theme);
-  $expanded-height: compatibility.private-density-prop-value(
-        expansion-variables.$header-density-config, $density-scale, expanded-height);
-  $collapsed-height: compatibility.private-density-prop-value(
-      expansion-variables.$header-density-config, $density-scale, collapsed-height);
 
-  @include compatibility.private-density-legacy-compatibility() {
-    .mat-expansion-panel-header {
-      height: $collapsed-height;
-
-      &.mat-expanded {
-        height: $expanded-height;
-      }
-    }
+  @include sass-utils.current-selector-or-root() {
+    @include token-utils.create-token-values(tokens-mat-expansion.$prefix,
+      tokens-mat-expansion.get-density-tokens($density-scale));
   }
 }
 

src/material/expansion/_expansion-theme.import.scss

@@ -1,4 +1,6 @@
 @use '@angular/cdk';
+@use '../core/tokens/m2/mat/expansion' as tokens-mat-expansion;
+@use '../core/tokens/token-utils';
 @use './expansion-variables';
 
 .mat-expansion-panel-header {
@@ -9,6 +11,44 @@
   border-radius: inherit;
   transition: height expansion-variables.$header-transition;
 
+  @include token-utils.use-tokens(
+    tokens-mat-expansion.$prefix, tokens-mat-expansion.get-token-slots()) {
+    @include token-utils.create-token-slot(height, header-collapsed-state-height);
+    @include token-utils.create-token-slot(font-family, header-text-font);
+    @include token-utils.create-token-slot(font-size, header-text-size);
+    @include token-utils.create-token-slot(font-weight, header-text-weight);
+    @include token-utils.create-token-slot(line-height, header-text-line-height);
+    @include token-utils.create-token-slot(letter-spacing, header-text-tracking);
+
+    &.mat-expanded {
+      @include token-utils.create-token-slot(height, header-expanded-state-height);
+    }
+
+    &[aria-disabled='true'] {
+      @include token-utils.create-token-slot(color, header-disabled-state-text-color);
+    }
+
+    &:not([aria-disabled='true']) {
+      cursor: pointer;
+
+      .mat-expansion-panel:not(.mat-expanded) &:hover {
+        @include token-utils.create-token-slot(background, header-hover-state-layer-color);
+
+        // Disable the hover on touch devices since it can appear like it is stuck. We can't use
+        // `@media (hover)` above, because the desktop support browser support isn't great.
+        @media (hover: none) {
+          @include token-utils.create-token-slot(background, container-background-color);
+        }
+      }
+
+      // The `.mat-expansion-panel` here is redundant, but we need the additional specificity.
+      .mat-expansion-panel &.cdk-keyboard-focused,
+      .mat-expansion-panel &.cdk-program-focused {
+        @include token-utils.create-token-slot(background, header-focus-state-layer-color);
+      }
+    }
+  }
+
   // If the `NoopAnimationsModule` is used, disable the height transition.
   &._mat-animation-noopable {
     transition: none;
@@ -24,10 +64,6 @@
     background: inherit;
   }
 
-  &:not([aria-disabled='true']) {
-    cursor: pointer;
-  }
-
   &.mat-expansion-toggle-indicator-before {
     flex-direction: row-reverse;
 
@@ -68,6 +104,13 @@
   }
 }
 
+.mat-expansion-panel-header-title {
+  @include token-utils.use-tokens(
+    tokens-mat-expansion.$prefix, tokens-mat-expansion.get-token-slots()) {
+    @include token-utils.create-token-slot(color, header-text-color);
+  }
+}
+
 .mat-expansion-panel-header-title,
 .mat-expansion-panel-header-description {
   display: flex;
@@ -80,10 +123,19 @@
     margin-right: 0;
     margin-left: 16px;
   }
+
+  .mat-expansion-panel-header[aria-disabled='true'] & {
+    color: inherit;
+  }
 }
 
 .mat-expansion-panel-header-description {
   flex-grow: 2;
+
+  @include token-utils.use-tokens(
+    tokens-mat-expansion.$prefix, tokens-mat-expansion.get-token-slots()) {
+    @include token-utils.create-token-slot(color, header-description-color);
+  }
 }
 
 // Creates the expansion indicator arrow. Done using ::after
@@ -96,6 +148,11 @@
   padding: 3px;
   transform: rotate(45deg);
   vertical-align: middle;
+
+  @include token-utils.use-tokens(
+    tokens-mat-expansion.$prefix, tokens-mat-expansion.get-token-slots()) {
+    @include token-utils.create-token-slot(color, header-indicator-color);
+  }
 }
 
 @include cdk.high-contrast(active, off) {