Ignore AlternateContent elements when there is no Fallback element

Author: mwilliamson

NEWS

@@ -3,6 +3,8 @@
 * Detect checkboxes, both as complex fields and structured document tags, and
   convert them to checkbox inputs.
 
+* Ignore AlternateContent elements when there is no Fallback element.
+
 # 1.8.0
 
 * Add style mapping for highlights.

mammoth/docx/body_xml.py

@@ -569,7 +569,7 @@ def read_comment_reference(element):
         return _success(documents.comment_reference(element.attributes["w:id"]))
 
     def alternate_content(element):
-        return read_child_elements(element.find_child("mc:Fallback"))
+        return read_child_elements(element.find_child_or_null("mc:Fallback"))
 
     def read_sdt(element):
         checkbox = element.find_child_or_null("w:sdtPr").find_child("wordml:checkbox")

tests/docx/body_xml_tests.py

@@ -1406,17 +1406,30 @@ def test_text_boxes_have_content_appended_after_containing_paragraph():
     result = _read_and_get_document_xml_elements(paragraph)
     assert_equal(result[1].style_id, "textbox-content")
 
-def test_alternate_content_is_read_using_fallback():
-    element = xml_element("mc:AlternateContent", {}, [
-        xml_element("mc:Choice", {"Requires": "wps"}, [
-            _paragraph_with_style_id("first")
-        ]),
-        xml_element("mc:Fallback", {}, [
-            _paragraph_with_style_id("second")
+
+class AlternateContentTests(object):
+    def test_when_fallback_is_present_then_fallback_is_read(self):
+        element = xml_element("mc:AlternateContent", {}, [
+            xml_element("mc:Choice", {"Requires": "wps"}, [
+                _paragraph_with_style_id("first")
+            ]),
+            xml_element("mc:Fallback", {}, [
+                _paragraph_with_style_id("second")
+            ])
         ])
-    ])
-    result = _read_and_get_document_xml_element(element)
-    assert_equal("second", result.style_id)
+        result = _read_and_get_document_xml_element(element)
+        assert_equal("second", result.style_id)
+
+
+    def test_when_fallback_is_not_present_then_element_is_ignored(self):
+        element = xml_element("mc:AlternateContent", {}, [
+            xml_element("mc:Choice", {"Requires": "wps"}, [
+                _paragraph_with_style_id("first")
+            ]),
+        ])
+        result = _read_and_get_document_xml_elements(element)
+        assert_equal([], result)
+
 
 def test_sdt_is_read_using_sdt_content():
     element = xml_element("w:sdt", {}, [