feat(select): do not emit styles when calling theme-styles(()).

PiperOrigin-RevId: 489980365

packages/mdc-select/_select-shared-theme.scss

@@ -34,11 +34,13 @@
 @function _resolve-theme-elevation($theme, $resolver) {
   $elevation: map.get($theme, menu-container-elevation);
   $shadow-color: map.get($theme, menu-container-shadow-color);
-  $resolved-value: meta.call(
-    $resolver,
-    $elevation: $elevation,
-    $shadow-color: $shadow-color
-  );
-  $theme: map.set($theme, menu-container-elevation, $resolved-value);
+  @if $elevation and $shadow-color {
+    $resolved-value: meta.call(
+      $resolver,
+      $elevation: $elevation,
+      $shadow-color: $shadow-color
+    );
+    $theme: map.set($theme, menu-container-elevation, $resolved-value);
+  }
   @return $theme;
 }

packages/mdc-select/_select-theme.scss

@@ -707,11 +707,13 @@ $_light-theme: (
 }
 
 @mixin _menu-container-elevation($elevation) {
-  .mdc-select__menu {
-    @include elevation-theme.shadow(map.get($elevation, shadow));
-    @include elevation-theme.overlay-opacity(
-      map.get($elevation, overlay-opacity)
-    );
+  @if $elevation {
+    .mdc-select__menu {
+      @include elevation-theme.shadow(map.get($elevation, shadow));
+      @include elevation-theme.overlay-opacity(
+        map.get($elevation, overlay-opacity)
+      );
+    }
   }
 }
 
@@ -975,7 +977,10 @@ $_light-theme: (
   $query: feature-targeting.all()
 ) {
   @if (meta.type-of($radius) == 'list' and list.length($radius) > 2) and
-    (list.nth($radius, 3) != 0 or list.nth($radius, 4) != 0)
+    (
+      (list.nth($radius, 3) != 0 and list.nth($radius, 3) != 0px) or
+        (list.nth($radius, 4) != 0 and list.nth($radius, 4) != 0px)
+    )
   {
     @error "mdc-select: Invalid radius #{$radius}. Only top-left and top-right corners may be customized.";
   }

packages/mdc-select/test/select-theme.test.scss

@@ -0,0 +1,37 @@
+@use 'third_party/javascript/material_components_web/tokens/v0_132/' as tokens;
+@use 'true' as test;
+
+@use '../select-filled-theme';
+@use '../select-outlined-theme';
+
+@include test.describe('select-filled-theme') {
+  @include test.describe('theme-styles()') {
+    @include test.it('return no styles when no theme is provided') {
+      @include test.assert {
+        @include test.output {
+          @include select-filled-theme.theme-styles(());
+        }
+
+        @include test.expect {
+          // No content. This is testing that an error isn't thrown.
+        }
+      }
+    }
+  }
+}
+
+@include test.describe('select-outlined-theme') {
+  @include test.describe('theme-styles()') {
+    @include test.it('return no styles when no theme is provided') {
+      @include test.assert {
+        @include test.output {
+          @include select-outlined-theme.theme-styles(());
+        }
+
+        @include test.expect {
+          // No content. This is testing that an error isn't thrown.
+        }
+      }
+    }
+  }
+}