Fixes IndexError in Component.from_ical()

CHANGES.rst

@@ -10,6 +10,9 @@ New:
 
 Fixes:
 
+- Fixed possible IndexError exception during parsing of an ical string.
+  [stlaz]
+
 - Fixed date-time being recognized as date or time during parsing. Added
   better error handling to parsing from ical strings.
   [stlaz]

src/icalendar/cal.py

@@ -362,7 +362,10 @@ class Component(CaselessDict):
             # we are adding properties to the current top of the stack
             else:
                 factory = types_factory.for_property(name)
-                component = stack[-1]
+                component = stack[-1] if stack else None
+                if not component:
+                    raise ValueError('Property "{prop}" does not have '
+                                     'a parent component.'.format(prop=name))
                 datetime_names = ('DTSTART', 'DTEND', 'RECURRENCE-ID', 'DUE',
                                   'FREEBUSY', 'RDATE', 'EXDATE')
                 try:

src/icalendar/tests/test_fixed_issues.py

@@ -360,3 +360,12 @@ END:VCALENDAR"""
             b'DTEND:20150905T100000Z\r\nUID:123\r\n'
             b'END:VEVENT\r\nEND:VCALENDAR\r\n'
         )
+
+    def test_index_error_issue(self):
+        """
+        Found an issue where from_ical() would raise IndexError for properties
+        without parent components
+        """
+
+        with self.assertRaises(ValueError):
+            cal = icalendar.Calendar.from_ical('VERSION:2.0')