Move all completion logic into a completion module.

keyring/cli.py

@@ -7,51 +7,27 @@
 
 from . import core
 from . import backend
+from . import completion
 from . import set_keyring, get_password, set_password, delete_password
 
-try:
-    import shtab
-except ImportError:
-    from . import _shtab as shtab
-
-# it completes keyring backends for `keyring -b` by the output of `keyring --list-backends`
-# % keyring -b <TAB>
-# keyring priority
-# keyring.backends.chainer.ChainerBackend   10
-# keyring.backends.fail.Keyring             0
-# ...                                       ...
-PREAMBLE = {
-    "zsh": r"""
-keyring_complete() {
-  local line
-  while read -r line; do
-    choices+=(${${line/ \(priority: /\\\\:}/)/})
-  done <<< "$($words[1] --list-backends)"
-  _arguments "*:keyring priority:(($choices))"
-}
-"""
-}
-KEYRING_COMPLETE = {"zsh": "keyring_complete"}
-
 
 class CommandLineTool:
     def __init__(self):
         self.parser = argparse.ArgumentParser()
-        shtab.add_argument_to(self.parser, preamble=PREAMBLE)
         self.parser.add_argument(
             "-p",
             "--keyring-path",
             dest="keyring_path",
             default=None,
             help="Path to the keyring backend",
-        ).complete = shtab.DIR
+        )
         self.parser.add_argument(
             "-b",
             "--keyring-backend",
             dest="keyring_backend",
             default=None,
             help="Name of the keyring backend",
-        ).complete = KEYRING_COMPLETE
+        )
         self.parser.add_argument(
             "--list-backends",
             action="store_true",
@@ -73,6 +49,7 @@ def __init__(self):
             'username',
             nargs="?",
         )
+        completion.install(self.parser)
 
     def run(self, argv):
         args = self.parser.parse_args(argv)

keyring/completion.py

@@ -0,0 +1,63 @@
+import argparse
+
+try:
+    import shtab
+except ImportError:
+    pass
+
+
+# it completes keyring backends for `keyring -b` by the output
+# of `keyring --list-backends`
+# % keyring -b <TAB>
+# keyring priority
+# keyring.backends.chainer.ChainerBackend   10
+# keyring.backends.fail.Keyring             0
+# ...                                       ...
+PREAMBLE = {
+    "zsh": r"""
+backend_complete() {
+  local line
+  while read -r line; do
+    choices+=(${${line/ \(priority: /\\\\:}/)/})
+  done <<< "$($words[1] --list-backends)"
+  _arguments "*:keyring priority:(($choices))"
+}
+"""
+}
+BACKEND_COMPLETE = {"zsh": "backend_complete"}
+
+
+class _MissingCompletionAction(argparse.Action):
+    def __call__(self, parser, namespace, values, option_string):
+        print("Install keyring[completion] for completion support.")
+        parser.exit(0)
+
+
+def add_completion_notice(parser):
+    """Add completion argument to parser."""
+    parser.add_argument(
+        "--print-completion",
+        choices=["bash", "zsh", "tcsh"],
+        action=_MissingCompletionAction,
+        help="print shell completion script",
+    )
+    return parser
+
+
+def get_action(parser, option):
+    (match,) = (action for action in parser._actions if option in action.option_strings)
+    return match
+
+
+def install(parser):
+    try:
+        install_completion(parser)
+    except NameError:
+        add_completion_notice(parser)
+
+
+def install_completion(parser):
+    shtab.add_argument_to(parser, preamble=PREAMBLE)
+    get_action(parser, '--keyring-path').completion = shtab.DIR
+    get_action(parser, '--keyring-backend').completion = BACKEND_COMPLETE
+    return parser

setup.cfg

@@ -64,7 +64,6 @@ docs =
 	# local
 
 completion =
-	# upstream
 	shtab
 
 [options.entry_points]