Follow w:numStyleLink in w:abstractNum

4 files changed, 45 insertions, 6 deletions

diff --git a/NEWS b/NEWS
index 31aeb23..8f23524 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,7 @@
+# 1.4.9
+
+* Improve list support by following w:numStyleLink in w:abstractNum.
+
 # 1.4.8
 
 * Preserve empty table rows.
diff --git a/mammoth/docx/__init__.py b/mammoth/docx/__init__.py
index 63a634c..fcb5da5 100644
--- a/mammoth/docx/__init__.py
+++ b/mammoth/docx/__init__.py
@@ -153,7 +153,7 @@ def _part_with_body_reader(document_path, zip_file, part_paths):
         zip_file,
         part_paths.numbering,
         lambda element: read_numbering_xml_element(element, styles=styles),
-        default=Numbering(abstract_nums={}, nums={}),
+        default=Numbering.EMPTY,
     )
 
     def read_part(name, reader, default=_undefined):
diff --git a/mammoth/docx/numbering_xml.py b/mammoth/docx/numbering_xml.py
index 3a0645e..af3d1d5 100644
--- a/mammoth/docx/numbering_xml.py
+++ b/mammoth/docx/numbering_xml.py
@@ -1,12 +1,13 @@
 import cobble
 
 from ..documents import numbering_level
+from .styles_xml import Styles
 
 
 def read_numbering_xml_element(element, styles):
     abstract_nums = _read_abstract_nums(element)
     nums = _read_nums(element)
-    return Numbering(abstract_nums=abstract_nums, nums=nums)
+    return Numbering(abstract_nums=abstract_nums, nums=nums, styles=styles)
 
 
 def _read_abstract_nums(element):
@@ -17,12 +18,14 @@ def _read_abstract_nums(element):
 def _read_abstract_num(element):
     abstract_num_id = element.attributes.get("w:abstractNumId")
     levels = _read_abstract_num_levels(element)
-    return abstract_num_id, _AbstractNum(levels=levels)
+    num_style_link = element.find_child_or_null("w:numStyleLink").attributes.get("w:val")
+    return abstract_num_id, _AbstractNum(levels=levels, num_style_link=num_style_link)
 
 
 @cobble.data
 class _AbstractNum(object):
     levels = cobble.field()
+    num_style_link = cobble.field()
 
 
 def _read_abstract_num_levels(element):
@@ -60,9 +63,10 @@ class _Num(object):
 
 
 class Numbering(object):
-    def __init__(self, abstract_nums, nums):
+    def __init__(self, abstract_nums, nums, styles):
         self._abstract_nums = abstract_nums
         self._nums = nums
+        self._styles = styles
 
     def find_level(self, num_id, level):
         num = self._nums.get(num_id)
@@ -70,4 +74,11 @@ class Numbering(object):
             return None
         else:
             abstract_num = self._abstract_nums[num.abstract_num_id]
-            return abstract_num.levels.get(level)
+            if abstract_num.num_style_link is None:
+                return abstract_num.levels.get(level)
+            else:
+                style = self._styles.find_numbering_style_by_id(abstract_num.num_style_link)
+                return self.find_level(style.num_id, level)
+
+
+Numbering.EMPTY = Numbering(abstract_nums={}, nums={}, styles=Styles.EMPTY)
diff --git a/tests/docx/numbering_xml_tests.py b/tests/docx/numbering_xml_tests.py
index 467d406..b707ba1 100644
--- a/tests/docx/numbering_xml_tests.py
+++ b/tests/docx/numbering_xml_tests.py
@@ -2,7 +2,7 @@ from nose.tools import istest, assert_equal
 
 from mammoth.docx.xmlparser import element as xml_element
 from mammoth.docx.numbering_xml import read_numbering_xml_element
-from mammoth.docx.styles_xml import Styles
+from mammoth.docx.styles_xml import NumberingStyle, Styles
 
 
 @istest
@@ -50,6 +50,30 @@ def find_level_returns_none_if_level_cannot_be_found():
     assert_equal(None, numbering.find_level("47", "2"))
 
 
+@istest
+def when_abstract_num_has_num_style_link_then_style_is_used_to_find_num():
+    numbering = _read_numbering_xml_element(
+        xml_element("w:numbering", {}, [
+            xml_element("w:abstractNum", {"w:abstractNumId": "100"}, [
+                xml_element("w:lvl", {"w:ilvl": "0"}, [
+                    xml_element("w:numFmt", {"w:val": "decimal"}),
+                ]),
+            ]),
+            xml_element("w:abstractNum", {"w:abstractNumId": "101"}, [
+                xml_element("w:numStyleLink", {"w:val": "List1"}),
+            ]),
+            xml_element("w:num", {"w:numId": "200"}, [
+                xml_element("w:abstractNumId", {"w:val": "100"}),
+            ]),
+            xml_element("w:num", {"w:numId": "201"}, [
+                xml_element("w:abstractNumId", {"w:val": "101"}),
+            ])
+        ]),
+        styles=Styles.create(numbering_styles={"List1": NumberingStyle(num_id="200")}),
+    )
+    assert_equal(True, numbering.find_level("201", "0").is_ordered)
+
+
 def _read_numbering_xml_element(element, styles=None):
     if styles is None:
         styles = Styles.EMPTY