email-print-mime-structure: add tab completion

This is modeled after the use of argcomplete in diffoscope, and it
should be possible to use it for any other pythonic mailscript that
uses argparse.

Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>

1 files changed, 15 insertions, 0 deletions

diff --git a/email-print-mime-structure b/email-print-mime-structure
index 5497597..aac8194 100755
--- a/email-print-mime-structure
+++ b/email-print-mime-structure
@@ -1,4 +1,5 @@
 #!/usr/bin/env python3
+# PYTHON_ARGCOMPLETE_OK
 # -*- coding: utf-8 -*-
 
 # Copyright (C) 2019 Daniel Kahn Gillmor
@@ -45,6 +46,11 @@ try:
 except ImportError:
     pgpy = None
 
+try:
+    import argcomplete #type: ignore
+except ImportError:
+    argcomplete = None
+
 class MimePrinter(object):
     def __init__(self, args:Namespace):
         self.args = args
@@ -152,6 +158,15 @@ def main() -> None:
     parser.add_argument('--use-gpg-agent', metavar='true|false', type=bool,
                         default=False,
                         help='Ask local GnuPG installation for decryption')
+
+    if argcomplete:
+        argcomplete.autocomplete(parser)
+    elif '_ARGCOMPLETE' in os.environ:
+        logging.error('Argument completion requested but the "argcomplete" '
+                      'module is not installed. '
+                      'Maybe you want to "apt install python3-argcomplete"')
+        sys.exit(1)
+
     args:Namespace = parser.parse_args()
     msg:Union[Message, str, int, Any] = email.message_from_file(sys.stdin)