From 3cbdaaedc226456a41825db84c303da205951d19 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sat, 27 Jan 2018 17:31:41 +0000
Subject: Find comments part using document relationships

---
 mammoth/docx/__init__.py | 39 +++++++++++++++++++++++++++++++++------
 tests/docx/docx_tests.py | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 6 deletions(-)

diff --git a/mammoth/docx/__init__.py b/mammoth/docx/__init__.py
index 5b21e18..e98d4b6 100644
--- a/mammoth/docx/__init__.py
+++ b/mammoth/docx/__init__.py
@@ -50,9 +50,23 @@ def _find_part_paths(zip_file):
     package_relationships = _read_relationships(zip_file, "_rels/.rels")
     document_filename = _find_document_filename(zip_file, package_relationships)
     
+    document_relationships = _read_relationships(
+        zip_file,
+        _find_relationships_path_for(document_filename),
+    )
+    
+    def find(name):
+        return _find_part_path(
+            zip_file=zip_file,
+            relationships=document_relationships,
+            relationship_type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/" + name,
+            fallback_path="word/{0}.xml".format(name),
+            base_path=zips.split_path(document_filename)[0],
+        )
+    
     return _PartPaths(
         main_document=document_filename,
-        comments="word/comments.xml",
+        comments=find("comments"),
         endnotes="word/endnotes.xml",
         footnotes="word/footnotes.xml",
         numbering="word/numbering.xml",
@@ -61,14 +75,27 @@ def _find_part_paths(zip_file):
 
 
 def _find_document_filename(zip_file, relationships):
-    office_document_type = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument"
+    path = _find_part_path(
+        zip_file,
+        relationships,
+        relationship_type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument",
+        base_path="",
+        fallback_path="word/document.xml",
+    )
+    if zip_file.exists(path):
+        return path
+    else:
+        raise IOError("Could not find main document part. Are you sure this is a valid .docx file?")
+
+
+def _find_part_path(zip_file, relationships, relationship_type, base_path, fallback_path):
     targets = [
-        target.lstrip("/")
-        for target in relationships.find_targets_by_type(office_document_type)
-    ] + ["word/document.xml"]
+        zips.join_path(base_path, target).lstrip("/")
+        for target in relationships.find_targets_by_type(relationship_type)
+    ]
     valid_targets = list(filter(lambda target: zip_file.exists(target), targets))
     if len(valid_targets) == 0:
-        raise IOError("Could not find main document part. Are you sure this is a valid .docx file?")
+        return fallback_path
     else:
         return valid_targets[0]
 
diff --git a/tests/docx/docx_tests.py b/tests/docx/docx_tests.py
index a474b17..64a3b81 100644
--- a/tests/docx/docx_tests.py
+++ b/tests/docx/docx_tests.py
@@ -101,6 +101,42 @@ class TestPartPaths(object):
         part_paths = self._find_part_paths(fileobj)
         assert_equal("word/document.xml", part_paths.main_document)
     
+    @istest
+    def comments_part_is_found_using_main_document_relationships(self):
+        fileobj = _create_zip({
+            "_rels/.rels": textwrap.dedent("""\
+                <?xml version="1.0" encoding="utf-8"?>
+                <Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">
+                    <Relationship Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="/word/document.xml" Id="rId1"/>
+                </Relationships>
+            """),
+            "word/document.xml": " ",
+            "word/_rels/document.xml.rels": textwrap.dedent("""\
+                <?xml version="1.0" encoding="utf-8"?>
+                <Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">
+                    <Relationship Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/comments" Target="target-path.xml" Id="rId2"/>
+                </Relationships>
+            """),
+            "word/target-path.xml": " "
+        })
+        part_paths = self._find_part_paths(fileobj)
+        assert_equal("word/target-path.xml", part_paths.comments)
+    
+    @istest
+    def when_relationship_for_comments_cannot_be_found_then_fallback_is_used(self):
+        fileobj = _create_zip({
+            "_rels/.rels": textwrap.dedent("""\
+                <?xml version="1.0" encoding="utf-8"?>
+                <Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">
+                    <Relationship Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="/word/document.xml" Id="rId1"/>
+                </Relationships>
+            """),
+            "word/document.xml": " ",
+        })
+        part_paths = self._find_part_paths(fileobj)
+        assert_equal("word/comments.xml", part_paths.comments)
+        
+    
     def _find_part_paths(self, fileobj):
         return docx._find_part_paths(zips.open_zip(fileobj, "r"))
 
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