until/every empty string should be mapped to None

Fix #999.

This also addresses a defect where editing a previously saved event
cause the 3 rrule properties (freq, until and interval) to have
incorrect default type (list instead of str), and freq value is forced
to lower case as the current code requires it but more important that is
how the values are presented in the interactive session.

khal/controllers.py

@@ -326,7 +326,7 @@ def new_interactive(collection, calendar_name, conf, info, location=None,
         except pytz.UnknownTimeZoneError:
             echo("unknown timezone")
 
-    info['description'] = prompt("description (or 'None')", default=info.get('description'))
+    info['description'] = prompt('description (or "None")', default=info.get('description'))
     if info['description'] == 'None':
         info['description'] = ''
 
@@ -413,6 +413,24 @@ def present_options(options, prefix="", sep="  ", width=70):
         return None
 
 
+def prompt_none(text, default=None, lower=False, type=None):
+    # icalendar.prop.vRecur returns list values for frequency, until and
+    # interval with one element.  However, when creating an event with
+    # new -i they are str values.
+    if isinstance(default, list):
+        default = default[0]
+
+    # icalendar.prop.vRecur return the freq value in upper case,
+    # however we only accept lower case values.  For consistency
+    # with the interactive mode conver the value for lowercase
+    # for display.
+    if isinstance(default, str) and lower:
+        default = default.lower()
+
+    v = prompt(text + ' (or "None")', default=default or "None", type=type)
+    return v if v != "None" else None
+
+
 def edit_event(event, collection, locale, allow_quit=False, width=80):
     options = OrderedDict()
     if allow_quit:
@@ -458,24 +476,14 @@ def edit_event(event, collection, locale, allow_quit=False, width=80):
             except:  # noqa
                 echo("error parsing range")
         elif choice == "repeat":
-            recur = event.recurobject
-            freq = recur["freq"] if "freq" in recur else ""
-            until = recur["until"] if "until" in recur else ""
-            interval = recur["interval"] if "interval" in recur else ""
-            if not freq:
-                freq = 'None'
-            freq = prompt('frequency (or "None")', freq)
-            if freq == 'None':
-                event.update_rrule(None)
-            else:
-                until = prompt('until (or "None")', until)
-                if until == 'None':
-                    until = None
-                interval = prompt('every (or "None")', interval)
-                if interval == 'None':
-                    interval = None
+            freq = prompt_none("frequency", event.recurobject.get("freq"), lower=True)
+            if freq:
+                until = prompt_none("until", event.recurobject.get("until"))
+                interval = prompt_none("interval", event.recurobject.get("interval"), int)
                 rrule = parse_datetime.rrulefstr(freq, until, interval, locale)
-                event.update_rrule(rrule)
+            else:
+                rrule = None
+            event.update_rrule(rrule)
             edited = True
         elif choice == "alarm":
             default_alarms = []

khal/parse_datetime.py

@@ -423,8 +423,8 @@ def rrulefstr(repeat, until, every, locale):
             try:
                 int(every)
             except ValueError:
-                logger.fatal("Invalid value for every option." +
-                        "Must be an integer")
+                logger.fatal("Invalid value for every option. " +
+                             "Must be an integer")
                 raise FatalError()
             rrule_settings['interval'] = every
         return rrule_settings