clang-format and clang-tidy scripts: More robust algorithm to find correct executable (#6041)

* More robust algorithm to find correct executable

* Revise message wording

* Add clang-tidy and clang-format to requirements.txt.
Add to message explaining install process.

* Extracted get_binary to helpers.py. Use execptions for clean exit.

* Add parameter types

* clang-{tidy,format} in requirements_test.txt
clean up script exit

* Kill processes on ^C

* Move clang-tidy and clang-format into requirements_dev.txt

script/clang-format

@@ -1,6 +1,12 @@
 #!/usr/bin/env python3
 
-from helpers import print_error_for_file, get_output, git_ls_files, filter_changed
+from helpers import (
+    print_error_for_file,
+    get_output,
+    git_ls_files,
+    filter_changed,
+    get_binary,
+)
 import argparse
 import click
 import colorama
@@ -13,11 +19,12 @@ import sys
 import threading
 
 
-def run_format(args, queue, lock, failed_files):
+
+def run_format(executable, args, queue, lock, failed_files):
     """Takes filenames out of queue and runs clang-format on them."""
     while True:
         path = queue.get()
-        invocation = ["clang-format-13"]
+        invocation = [executable]
         if args.inplace:
             invocation.append("-i")
         else:
@@ -58,22 +65,6 @@ def main():
     )
     args = parser.parse_args()
 
-    try:
-        get_output("clang-format-13", "-version")
-    except:
-        print(
-            """
-        Oops. It looks like clang-format is not installed. 
-        
-        Please check you can run "clang-format-13 -version" in your terminal and install
-        clang-format (v13) if necessary.
-        
-        Note you can also upload your code as a pull request on GitHub and see the CI check
-        output to apply clang-format.
-        """
-        )
-        return 1
-
     files = []
     for path in git_ls_files(["*.cpp", "*.h", "*.tcc"]):
         files.append(os.path.relpath(path, os.getcwd()))
@@ -90,11 +81,12 @@ def main():
 
     failed_files = []
     try:
+        executable = get_binary("clang-format", 13)
         task_queue = queue.Queue(args.jobs)
         lock = threading.Lock()
         for _ in range(args.jobs):
             t = threading.Thread(
-                target=run_format, args=(args, task_queue, lock, failed_files)
+                target=run_format, args=(executable, args, task_queue, lock, failed_files)
             )
             t.daemon = True
             t.start()
@@ -109,13 +101,18 @@ def main():
         # Wait for all threads to be done.
         task_queue.join()
 
+    except FileNotFoundError as ex:
+        return 1
     except KeyboardInterrupt:
         print()
         print("Ctrl-C detected, goodbye.")
+        # Kill subprocesses (and ourselves!)
+        # No simple, clean alternative appears to be available.
         os.kill(0, 9)
+        return 2    # Will not execute.
 
-    sys.exit(len(failed_files))
+    return len(failed_files)
 
 
 if __name__ == "__main__":
-    main()
+    sys.exit(main())