Allow `=` in parameter values.

Some parameter values (e.g., BASE64 encoded binary data often ends with
one or two equal signs) may contain an equal sign (`=`). The current
implementation splits key-value pairs at all equal signs, which leads to
errors. Especially icalendar files generated by Apple's software often
feature BASE64 encoded binary data in parameter values.

This patch introduces a new parameter `maxsplit` to
icalendar.parser.q_split() which works similar as python's
string.split(sep, maxsplit) which we then use to split parameter
key-value pairs only at the first equal sign.

This patch fixes #197.

CHANGES.rst

@@ -14,7 +14,8 @@ New features:
 
 Bug fixes:
 
-- *add item here*
+- Don't break on parameter values which contain equal signs, e.g. base64 encoded
+  binary data [geier]
 
 
 3.11.3 (2017-02-15)

src/icalendar/parser.py

@@ -149,13 +149,14 @@ def dquote(val):
 
 
 # parsing helper
-def q_split(st, sep=','):
+def q_split(st, sep=',', maxsplit=-1):
     """Splits a string on char, taking double (q)uotes into considderation.
     """
     result = []
     cursor = 0
     length = len(st)
     inquote = 0
+    splits = 0
     for i in range(length):
         ch = st[i]
         if ch == '"':
@@ -163,8 +164,10 @@ def q_split(st, sep=','):
         if not inquote and ch == sep:
             result.append(st[cursor:i])
             cursor = i + 1
-        if i + 1 == length:
+            splits += 1
+        if i + 1 == length or splits == maxsplit:
             result.append(st[cursor:])
+            break
     return result
 
 
@@ -227,7 +230,7 @@ class Parameters(CaselessDict):
         result = cls()
         for param in q_split(st, ';'):
             try:
-                key, val = q_split(param, '=')
+                key, val = q_split(param, '=', maxsplit=1)
                 validate_token(key)
                 # Property parameter values that are not in quoted
                 # strings are case insensitive.

src/icalendar/tests/apple_xlocation_test.py

@@ -10,17 +10,11 @@ class TestEncoding(unittest.TestCase):
 
     def test_apple_xlocation(self):
         """
-        Test if error messages are encode properly.
+        Test if we support base64 encoded binary data in parameter values.
         """
-        try:
-            directory = os.path.dirname(__file__)
-            with open(os.path.join(directory, 'x_location.ics'), 'rb') as fp:
-                data = fp.read()
-            cal = icalendar.Calendar.from_ical(data)
-            for event in cal.walk('vevent'):
-                self.assertEqual(len(event.errors), 1, 'Got too many errors')
-                error = event.errors[0][1]
-                self.assertTrue(error.startswith(u'Content line could not be parsed into parts'))
-
-        except UnicodeEncodeError as e:
-            self.fail("There is something wrong with encoding in the collected error messages")
+        directory = os.path.dirname(__file__)
+        with open(os.path.join(directory, 'x_location.ics'), 'rb') as fp:
+            data = fp.read()
+        cal = icalendar.Calendar.from_ical(data)
+        for event in cal.walk('vevent'):
+            self.assertEqual(len(event.errors), 0, 'Got too many errors')

src/icalendar/tests/test_icalendar.py

@@ -1,4 +1,6 @@
 # -*- coding: utf-8 -*-
+import textwrap
+
 from icalendar.tests import unittest
 
 
@@ -207,6 +209,30 @@ class IcalendarTestCase (unittest.TestCase):
             ('key', Parameters({'PARAM': 'pValue'}), 'value')
         )
 
+        contains_base64 = (
+            'X-APPLE-STRUCTURED-LOCATION;'
+            'VALUE=URI;X-ADDRESS="Kaiserliche Hofburg, 1010 Wien";'
+            'X-APPLE-MAPKIT-HANDLE=CAESxQEZgr3QZXJyZWljaA==;'
+            'X-APPLE-RADIUS=328.7978217977285;X-APPLE-REFERENCEFRAME=1;'
+            'X-TITLE=Heldenplatz:geo:48.206686,16.363235'
+        ).encode('utf-8')
+
+        self.assertEqual(
+            Contentline(contains_base64, strict=True).parts(),
+            ('X-APPLE-STRUCTURED-LOCATION',
+             Parameters({
+                 'X-APPLE-RADIUS': '328.7978217977285',
+                 'X-ADDRESS': 'Kaiserliche Hofburg, 1010 Wien',
+                 'X-APPLE-REFERENCEFRAME': '1',
+                 'X-TITLE': u'HELDENPLATZ',
+                 'X-APPLE-MAPKIT-HANDLE':
+                 'CAESXQEZGR3QZXJYZWLJAA==',
+                 'VALUE': 'URI',
+             }),
+             'geo:48.206686,16.363235'
+             )
+        )
+
     def test_fold_line(self):
         from ..parser import foldline
 
@@ -247,6 +273,10 @@ class IcalendarTestCase (unittest.TestCase):
         self.assertEqual(q_split('Max,Moller,"Rasmussen, Max"'),
                          ['Max', 'Moller', '"Rasmussen, Max"'])
 
+    def test_q_split_bin(self):
+        from ..parser import q_split
+        self.assertEqual(q_split('X-SOMETHING=ABCDE==', '=', maxsplit=1), ['X-SOMETHING', 'ABCDE=='])
+
     def test_q_join(self):
         from ..parser import q_join
         self.assertEqual(q_join(['Max', 'Moller', 'Rasmussen, Max']),