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.

2 files changed, 14 insertions, 3 deletions

diff --git a/alot/commands/thread.py b/alot/commands/thread.py
index fc6a4273..33230197 100644
--- a/alot/commands/thread.py
+++ b/alot/commands/thread.py
@@ -537,7 +537,8 @@ class EditNewCommand(Command):
                             'nargs': '*'})])
 @registerCommand(
     MODE, 'indent', help='change message/reply indentation',
-    arguments=[(['indent'], {})])
+    arguments=[(['indent'], {'action': cargparse.ValidatedStoreAction,
+                             'validator': cargparse.is_int_or_pm})])
 class ChangeDisplaymodeCommand(Command):
 
     """fold or unfold messages"""
@@ -576,8 +577,8 @@ class ChangeDisplaymodeCommand(Command):
             elif self.indent == '-':
                 tbuffer._indent_width -= 1
             else:
-                # TODO: I'm dangerous
-                tbuffer._indent_width = int(self.indent)
+                # argparse validation guarantees that self.indent is an integer
+                tbuffer._indent_width = self.indent
             tbuffer.rebuild()
             tbuffer.collapse_all()
             ui.update()
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):