Fix removing comments in rule if they are only children

Author: hudochenkov

index.js

@@ -222,8 +222,10 @@ module.exports = postcss.plugin('postcss-sorting', function (opts) {
                     return a.initialIndex - b.initialIndex;
                 });
 
-                rule.removeAll();
-                rule.append(processed);
+                if (processed.length) {
+                    rule.removeAll();
+                    rule.append(processed);
+                }
 
                 // Remove all empty lines and add empty lines between groups
                 rule.each(function (node) {

test/fixtures/rules-with-comments-only.css

@@ -0,0 +1,16 @@
+div {
+    /* comment 1*/
+}
+
+section {
+    /* comment 2 */
+    a {
+        /* comment 3 */
+    }
+}
+
+article {
+    @media (min-width: 300px) {
+        /* comment 4 */
+    }
+}

test/fixtures/rules-with-comments-only.expected.css

@@ -0,0 +1,16 @@
+div {
+    /* comment 1*/
+}
+
+section {
+    /* comment 2 */
+    a {
+        /* comment 3 */
+    }
+}
+
+article {
+    @media (min-width: 300px) {
+        /* comment 4 */
+    }
+}

test/test.js

@@ -62,6 +62,10 @@ test('Should work correctly with comments in case of 1 group', t => {
     ] });
 });
 
+test('Should not remove comments in rules if they are only children', t => {
+    return run(t, 'rules-with-comments-only');
+});
+
 test('Should work correctly with one comment in case of 1 group. SCSS syntax', t => {
     return run(t, 'single-group-comment-scss.scss', { 'sort-order': [
         ['border-bottom', 'font-style']