sanitize parameter for thread mode command 'indent'

this introduces a new argparse validation check that makes sure a
parameter is '+', '-', or an integer, and uses this check for the
'indent' thread mode command.

1 files changed, 10 insertions, 0 deletions

diff --git a/alot/utils/argparse.py b/alot/utils/argparse.py
index adacdd6e..ff19030c 100644
--- a/alot/utils/argparse.py
+++ b/alot/utils/argparse.py
@@ -97,6 +97,16 @@ def require_dir(path):
         raise ValidationFailed('{} is not a valid directory.'.format(path))
 
 
+def is_int_or_pm(value):
+    """Validator to assert that value is '+', '-', or an integer"""
+    if value not in ['+', '-']:
+        try:
+            value = int(value)
+        except ValueError:
+            raise ValidationFailed('value must be an integer or "+" or "-".')
+    return value
+
+
 class BooleanAction(argparse.Action):
     """Argparse action that can be used to store boolean values."""
     def __init__(self, *args, **kwargs):