Auto merge of #13447 - gterzian:check_webidls_folder_files, r=Wafflespeanut

Have tidy ensure that the there are no extra files in the webidls folder #13427

<!-- Please describe your changes on the following line: -->
 Have tidy ensure that the there are no extra files in the webidls folder #13427

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #13427 (github issue number if applicable).

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- [x] There are tests for these changes

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python/tidy/servo_tidy_tests/test_tidy.py

@@ -9,6 +9,7 @@
 
 import os
 import unittest
+
 from servo_tidy import tidy
 
 base_path = 'servo_tidy_tests/' if os.path.exists('servo_tidy_tests/') else 'python/tidy/servo_tidy_tests/'
@@ -30,6 +31,17 @@ class CheckTidiness(unittest.TestCase):
         self.assertEqual('invalid config table [wrong]', errors.next()[2])
         self.assertNoMoreErrors(errors)
 
+    def test_directory_checks(self):
+        dirs = {
+            os.path.join(base_path, "dir_check/webidl_plus"): ['webidl', 'test'],
+            os.path.join(base_path, "dir_check/only_webidl"): ['webidl']
+            }
+        errors = tidy.check_directory_files(dirs)
+        error_dir = os.path.join(base_path, "dir_check/webidl_plus")
+        self.assertEqual("Unexpected extension found for test.rs. We only expect files with webidl, test extensions in {0}".format(error_dir), errors.next()[2])
+        self.assertEqual("Unexpected extension found for test2.rs. We only expect files with webidl, test extensions in {0}".format(error_dir), errors.next()[2])
+        self.assertNoMoreErrors(errors)
+
     def test_spaces_correctnes(self):
         errors = tidy.collect_errors_for_files(iterFile('wrong_space.rs'), [], [tidy.check_by_line], print_text=False)
         self.assertEqual('trailing whitespace', errors.next()[2])