Auto merge of #13986 - iamrohit7:tidy-feature-attrs, r=Wafflespeanut

Make test-tidy check for alphabetical ordering of #![feature(...)] statements

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [x] These changes fix #13954  (github issue number if applicable).

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- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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2 files changed, 22 insertions, 0 deletions

diff --git a/python/tidy/servo_tidy_tests/lib.rs b/python/tidy/servo_tidy_tests/lib.rs
new file mode 100644
index 00000000000..4ca395d8e6d
--- /dev/null
+++ b/python/tidy/servo_tidy_tests/lib.rs
@@ -0,0 +1,14 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#![feature(def)]
+#![feature(abc)]
+
+#![feature(abc, def, ghi)]
+#![feature(aaa)]
+
+#![feature(def, ghi, abc)]
+
+#![feature(ghi)]
+#![feature(abd, hef)]
diff --git a/python/tidy/servo_tidy_tests/test_tidy.py b/python/tidy/servo_tidy_tests/test_tidy.py
index 7bec2c61718..d997bb00f82 100644
--- a/python/tidy/servo_tidy_tests/test_tidy.py
+++ b/python/tidy/servo_tidy_tests/test_tidy.py
@@ -127,6 +127,14 @@ class CheckTidiness(unittest.TestCase):
         self.assertEqual('extra space after test_fun', errors.next()[2])
         self.assertNoMoreErrors(errors)
 
+        feature_errors = tidy.collect_errors_for_files(iterFile('lib.rs'), [], [tidy.check_rust], print_text=False)
+
+        self.assertTrue('feature attribute is not in alphabetical order' in feature_errors.next()[2])
+        self.assertTrue('feature attribute is not in alphabetical order' in feature_errors.next()[2])
+        self.assertTrue('feature attribute is not in alphabetical order' in feature_errors.next()[2])
+        self.assertTrue('feature attribute is not in alphabetical order' in feature_errors.next()[2])
+        self.assertNoMoreErrors(feature_errors)
+
     def test_spec_link(self):
         tidy.SPEC_BASE_PATH = base_path
         errors = tidy.collect_errors_for_files(iterFile('speclink.rs'), [], [tidy.check_spec], print_text=False)