Handle AlternateContent without Fallback in office_xml

Author: mwilliamson

mammoth/docx/office_xml.py

@@ -37,7 +37,7 @@ def read(fileobj):
 def _collapse_alternate_content(node):
     if isinstance(node, XmlElement):
         if node.name == "mc:AlternateContent":
-            return node.find_child("mc:Fallback").children
+            return node.find_child_or_null("mc:Fallback").children
         else:
             node.children = flat_map(_collapse_alternate_content, node.children)
             return [node]

tests/docx/office_xml_tests.py

@@ -6,19 +6,35 @@
 from ..testing import assert_equal
 
 
-def test_alternate_content_is_replaced_by_contents_of_fallback():
-    xml_string = (
-        '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' +
-        '<numbering xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006">' +
-        '<mc:AlternateContent>' +
-        '<mc:Choice Requires="w14">' +
-        '<choice/>' +
-        '</mc:Choice>' +
-        '<mc:Fallback>' +
-        '<fallback/>' +
-        '</mc:Fallback>' +
-        '</mc:AlternateContent>' +
-        '</numbering>')
-
-    result = office_xml.read(io.StringIO(xml_string))
-    assert_equal([xml.element("fallback")], result.children)
+class AlternateContentTests(object):
+    def test_when_fallback_is_present_then_fallback_is_read(self):
+        xml_string = (
+            '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' +
+            '<numbering xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006">' +
+            '<mc:AlternateContent>' +
+            '<mc:Choice Requires="w14">' +
+            '<choice/>' +
+            '</mc:Choice>' +
+            '<mc:Fallback>' +
+            '<fallback/>' +
+            '</mc:Fallback>' +
+            '</mc:AlternateContent>' +
+            '</numbering>')
+
+        result = office_xml.read(io.StringIO(xml_string))
+        assert_equal([xml.element("fallback")], result.children)
+
+
+    def test_when_fallback_is_not_present_then_element_is_ignored(self):
+        xml_string = (
+            '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' +
+            '<numbering xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006">' +
+            '<mc:AlternateContent>' +
+            '<mc:Choice Requires="w14">' +
+            '<choice/>' +
+            '</mc:Choice>' +
+            '</mc:AlternateContent>' +
+            '</numbering>')
+
+        result = office_xml.read(io.StringIO(xml_string))
+        assert_equal([], result.children)