refactor(material/core): remove underscores from symbols consumed in other files (#20906)

In the new Sass module system a symbol prefixed with an underscore means that it's
private and it can't be used in other files. These changes refactor all of our existing
usages to remove the underscore. Some of the symbols have been moved into
`private` directories to make it more obvious that they shouldn't be depended upon.

Author: crisbeto

src/dev-app/theme.scss

@@ -1,5 +1,5 @@
 @import '../material/core/color/all-color';
-@import '../material/core/density/all-density';
+@import '../material/core/density/private';
 @import '../material/core/focus-indicators/focus-indicators';
 @import '../material/core/theming/all-theme';
 @import '../material-experimental/column-resize/column-resize';
@@ -88,7 +88,7 @@ $dark-theme: mat-dark-theme((
 $density-scales: (-1, -2, minimum, maximum);
 @each $density in$density-scales {
   .demo-density-#{$density} {
-    @include _angular-material-density($density);
+    @include angular-material-density($density);
     @include angular-material-mdc-density($density);
   }
 }

src/material-experimental/column-resize/_column-resize.scss

@@ -1,6 +1,6 @@
 @import '../../material/core/style/variables';
 @import '../../material/core/style/vendor-prefixes';
-@import '../../material/core/theming/check-duplicate-styles';
+@import '../../material/core/theming/private';
 @import '../../material/core/theming/palette';
 @import '../../material/core/theming/theming';
 
@@ -103,8 +103,8 @@
 @mixin mat-column-resize-density($config-or-theme) {}
 
 @mixin mat-column-resize-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-column-resize') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-column-resize') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-autocomplete/_autocomplete-theme.scss

@@ -26,8 +26,8 @@
 @mixin mat-mdc-autocomplete-density($config-or-theme) {}
 
 @mixin mat-mdc-autocomplete-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-autocomplete') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-autocomplete') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-button/_button-theme.scss

@@ -183,8 +183,8 @@ $mat-button-state-target: '.mdc-button__ripple';
 }
 
 @mixin mat-mdc-button-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-button') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-button') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);
@@ -261,8 +261,8 @@ $mat-button-state-target: '.mdc-button__ripple';
 @mixin mat-mdc-fab-density($config-or-theme) {}
 
 @mixin mat-mdc-fab-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-fab') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-fab') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);
@@ -339,8 +339,8 @@ $mat-button-state-target: '.mdc-button__ripple';
 }
 
 @mixin mat-mdc-icon-button-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-icon-button') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-icon-button') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-card/_card-theme.scss

@@ -51,8 +51,8 @@
 @mixin mat-mdc-card-density($config-or-theme) {}
 
 @mixin mat-mdc-card-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-card') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-card') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-checkbox/_checkbox-theme.scss

@@ -98,8 +98,8 @@
 }
 
 @mixin mat-mdc-checkbox-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-checkbox') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-checkbox') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-chips/_chips-theme.scss

@@ -71,8 +71,8 @@
 }
 
 @mixin mat-mdc-chips-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-chips') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-chips') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-color/_all-color.scss

@@ -3,7 +3,7 @@
 @mixin angular-material-mdc-color($config-or-theme) {
   // In case a theme object has been passed instead of a configuration for
   // the color system, extract the color config from the theme object.
-  $config: if(_mat-is-theme-object($config-or-theme),
+  $config: if(mat-private-is-theme-object($config-or-theme),
       mat-get-color-config($config-or-theme), $config-or-theme);
 
   @if $config == null {

src/material-experimental/mdc-core/_core.scss

@@ -1,14 +1,14 @@
-@import '../../material/core/theming/check-duplicate-styles';
+@import '../../material/core/theming/private';
 @import './option/option-theme';
 @import './option/optgroup-theme';
 
 // Mixin that renders all of the core styles that depend on the theme.
 @mixin mat-mdc-core-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
   // Wrap the sub-theme includes in the duplicate theme styles mixin. This ensures that
   // there won't be multiple warnings. e.g. if `mat-mdc-core-theme` reports a warning, then
   // the imported themes (such as `mat-ripple-theme`) should not report again.
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-core') {
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-core') {
     @include mat-mdc-option-theme($theme);
     @include mat-mdc-optgroup-theme($theme);
   }

src/material-experimental/mdc-core/option/_optgroup-theme.scss

@@ -2,7 +2,7 @@
 @import '@material/list/variables.import';
 @import '@material/theme/functions.import';
 @import '../../mdc-helpers/mdc-helpers';
-@import '../../../material/core/theming/check-duplicate-styles';
+@import '../../../material/core/theming/private';
 
 @mixin mat-mdc-optgroup-color($config-or-theme) {
   $config: mat-get-color-config($config-or-theme);
@@ -27,8 +27,8 @@
 }
 
 @mixin mat-mdc-optgroup-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-optgroup') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-optgroup') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-core/option/_option-theme.scss

@@ -2,7 +2,7 @@
 @import '@material/list/variables.import';
 @import '@material/theme/functions.import';
 @import '../../mdc-helpers/mdc-helpers';
-@import '../../../material/core/theming/check-duplicate-styles';
+@import '../../../material/core/theming/private';
 
 @mixin mat-mdc-option-color($config-or-theme) {
   $config: mat-get-color-config($config-or-theme);
@@ -49,8 +49,8 @@
 }
 
 @mixin mat-mdc-option-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-option') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-option') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-density/_all-density.scss

@@ -3,7 +3,7 @@
 @mixin angular-material-mdc-density($config-or-theme) {
   // In case a theme object has been passed instead of a configuration for
   // the density system, extract the density config from the theme object.
-  $config: if(_mat-is-theme-object($config-or-theme),
+  $config: if(mat-private-is-theme-object($config-or-theme),
       mat-get-density-config($config-or-theme), $config-or-theme);
 
   @if $config == null {

src/material-experimental/mdc-dialog/_dialog-theme.scss

@@ -20,8 +20,8 @@
 }
 
 @mixin mat-mdc-dialog-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-dialog') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-dialog') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-form-field/_form-field-theme.scss

@@ -79,8 +79,8 @@
 }
 
 @mixin mat-mdc-form-field-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-form-field') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-form-field') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-helpers/_focus-indicators.scss

@@ -120,8 +120,8 @@
     @include _mat-mdc-strong-focus-indicators-border-color($theme-or-color);
   }
   @else {
-    $theme: _mat-legacy-get-theme($theme-or-color);
-    @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-strong-focus-indicators') {
+    $theme: mat-private-legacy-get-theme($theme-or-color);
+    @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-strong-focus-indicators') {
       $color: mat-get-color-config($theme);
       @if $color != null {
         @include mat-mdc-strong-focus-indicators-color($color);

src/material-experimental/mdc-helpers/_mdc-helpers.scss

@@ -8,7 +8,7 @@
 @import '@material/typography/variables.import';
 @import '../../material/core/style/layout-common';
 @import '../../material/core/theming/theming';
-@import '../../material/core/theming/check-duplicate-styles';
+@import '../../material/core/theming/private';
 @import '../../material/core/typography/typography';
 
 // A set of standard queries to use with MDC's queryable mixins.

src/material-experimental/mdc-input/_input-theme.scss

@@ -13,8 +13,8 @@
 @mixin mat-mdc-input-density($config-or-theme) {}
 
 @mixin mat-mdc-input-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-input') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-input') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-list/_list-theme.scss

@@ -60,8 +60,8 @@
 }
 
 @mixin mat-mdc-list-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-list') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-list') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-menu/_menu-theme.scss

@@ -55,8 +55,8 @@
 @mixin mat-mdc-menu-density($config-or-theme) {}
 
 @mixin mat-mdc-menu-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-menu') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-menu') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-paginator/_paginator-theme.scss

@@ -1,6 +1,6 @@
 @import '@material/theme/variables.import';
 @import '@material/typography/variables.import';
-@import '../../material/core/theming/check-duplicate-styles';
+@import '../../material/core/theming/private';
 @import './paginator-variables';
 
 @mixin mat-mdc-paginator-color($config-or-theme) {
@@ -55,18 +55,18 @@
 
 @mixin mat-mdc-paginator-density($config-or-theme) {
   $density-scale: mat-get-density-config($config-or-theme);
-  $height: _mat-density-prop-value($mat-paginator-density-config, $density-scale, height);
+  $height: mat-private-density-prop-value($mat-paginator-density-config, $density-scale, height);
 
-  @include _mat-density-legacy-compatibility() {
+  @include mat-private-density-legacy-compatibility() {
     .mat-mdc-paginator-container {
       min-height: $height;
     }
   }
 }
 
 @mixin mat-mdc-paginator-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-paginator') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-paginator') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-progress-bar/_progress-bar-theme.scss

@@ -34,8 +34,8 @@
 @mixin mat-mdc-progress-bar-density($config-or-theme) {}
 
 @mixin mat-mdc-progress-bar-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-progress-bar') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-progress-bar') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-progress-spinner/_progress-spinner-theme.scss

@@ -27,8 +27,8 @@
 @mixin mat-mdc-progress-spinner-density($config-or-theme) {}
 
 @mixin mat-mdc-progress-spinner-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-progress-spinner') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-progress-spinner') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-radio/_radio-theme.scss

@@ -54,8 +54,8 @@
 }
 
 @mixin mat-mdc-radio-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-radio') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-radio') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-select/_select-theme.scss

@@ -95,8 +95,8 @@
 @mixin mat-mdc-select-density($config-or-theme) {}
 
 @mixin mat-mdc-select-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-select') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-select') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-sidenav/_sidenav-theme.scss

@@ -9,8 +9,8 @@
 }
 
 @mixin mat-mdc-sidenav-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-sidenav') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-sidenav') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-slide-toggle/_slide-toggle-theme.scss

@@ -94,8 +94,8 @@
 }
 
 @mixin mat-mdc-slide-toggle-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-slide-toggle') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-slide-toggle') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-slider/_slider-theme.scss

@@ -33,8 +33,8 @@
 @mixin mat-mdc-slider-density($config-or-theme) {}
 
 @mixin mat-mdc-slider-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-slider') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-slider') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-snack-bar/_snack-bar-theme.scss

@@ -43,8 +43,8 @@
 @mixin mat-mdc-snack-bar-density($config-or-theme) {}
 
 @mixin mat-mdc-snack-bar-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-snack-bar') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-snack-bar') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);

src/material-experimental/mdc-table/_table-theme.scss

@@ -57,8 +57,8 @@
 }
 
 @mixin mat-mdc-table-theme($theme-or-color-config) {
-  $theme: _mat-legacy-get-theme($theme-or-color-config);
-  @include _mat-check-duplicate-theme-styles($theme, 'mat-mdc-table') {
+  $theme: mat-private-legacy-get-theme($theme-or-color-config);
+  @include mat-private-check-duplicate-theme-styles($theme, 'mat-mdc-table') {
     $color: mat-get-color-config($theme);
     $density: mat-get-density-config($theme);
     $typography: mat-get-typography-config($theme);