documentation_tests.txt - sort filenames alphabetically (#24647)

* Sort filenames alphabetically

* Add check for order

utils/check_doctest_list.py

@@ -24,12 +24,16 @@ REPO_PATH = "."
 if __name__ == "__main__":
     doctest_file_path = os.path.join(REPO_PATH, "utils/documentation_tests.txt")
     non_existent_paths = []
+    all_paths = []
     with open(doctest_file_path) as fp:
         for line in fp:
             line = line.strip()
             path = os.path.join(REPO_PATH, line)
             if not (os.path.isfile(path) or os.path.isdir(path)):
                 non_existent_paths.append(line)
+            all_paths.append(path)
     if len(non_existent_paths) > 0:
         non_existent_paths = "\n".join(non_existent_paths)
         raise ValueError(f"`utils/documentation_tests.txt` contains non-existent paths:\n{non_existent_paths}")
+    if all_paths != sorted(all_paths):
+        raise ValueError("Files in `utils/documentation_tests.txt` are not in alphabetical order.")