fix(rtl): mixins work with pseudo elements

PiperOrigin-RevId: 370770101

packages/mdc-rtl/_rtl.scss

@@ -25,7 +25,9 @@
 
 @use 'sass:list';
 @use 'sass:meta';
+@use 'sass:selector';
 @use '@material/theme/theme';
+@use '@material/theme/selector-ext';
 
 $include: true !default;
 
@@ -70,9 +72,17 @@ $include: true !default;
 /// @content Content to be styled in an RTL context.
 @mixin rtl() {
   @if ($include) {
-    [dir='rtl'] &,
-    &[dir='rtl'] {
-      @content;
+    $dir-rtl: '[dir=rtl]';
+
+    $rtl-selectors: list.join(
+      selector.nest($dir-rtl, &),
+      selector-ext.append-strict(&, $dir-rtl)
+    );
+
+    @at-root {
+      #{$rtl-selectors} {
+        @content;
+      }
     }
   }
 }

packages/mdc-rtl/test/rtl.scss.test.ts

@@ -0,0 +1,39 @@
+/**
+ * @license
+ * Copyright 2020 Google Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+import * as fs from 'fs';
+import * as path from 'path';
+
+describe('rtl.test.scss', () => {
+  let css = '';
+
+  beforeAll(() => {
+    const filePath = path.join(__dirname, 'rtl.test.css');
+    css = fs.readFileSync(filePath, 'utf8').trim();
+  });
+
+  it('should not add [dir=rtl] after pseudo element', () => {
+    expect(css).not.toContain('.test-pseudo-element::before[dir=rtl]');
+    expect(css).toContain('.test-pseudo-element[dir=rtl]::before');
+  });
+});

packages/mdc-rtl/test/rtl.test.scss

@@ -0,0 +1,9 @@
+@use '../rtl';
+
+.test-pseudo-element {
+  &::before {
+    @include rtl.rtl {
+      margin-right: 0;
+    }
+  }
+}