From c178ed2106e0e6943eed8f39b7d91e12db09e6fb Mon Sep 17 00:00:00 2001
From: Greg Kempe <greg@kempe.net>
Date: Fri, 23 Oct 2020 09:53:56 +0200
Subject: [PATCH 1/3] Make it possible to adjust the attributes used when
 comparing nodes.

Subclasses can use this determine which attributes for a node should be
considered when diffing. By default, they are all considered.
---
 CHANGES.rst        |  2 +-
 tests/test_diff.py | 21 +++++++++++++++++++++
 xmldiff/diff.py    | 11 ++++++++---
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/CHANGES.rst b/CHANGES.rst
index b56bebd..5d79429 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -4,7 +4,7 @@ Changes
 2.5 (unreleased)
 ----------------
 
-- Nothing changed yet.
+- Make it possible to adjust the attributes considered when comparing nodes.
 
 
 2.4 (2019-10-09)
diff --git a/tests/test_diff.py b/tests/test_diff.py
index 643e941..07155a4 100644
--- a/tests/test_diff.py
+++ b/tests/test_diff.py
@@ -1458,3 +1458,24 @@ def test_issue_21_default_namespaces(self):
         right = '<tag xmlns="ns">new</tag>'
         result = self._diff(left, right)
         self.assertEqual(result[0].node, "/*[1]")
+
+    def test_ignore_attribute(self):
+        # this differ ignores the attribute 'skip' when diffing
+        class IgnoringDiffer(Differ):
+            def node_attribs(self, node):
+                if 'skip' in node.attrib:
+                    attribs = dict(node.attrib)
+                    del attribs['skip']
+                    return attribs
+                return node.attrib
+
+        left = '<a><b foo="bar" skip="boom">text</b></a>'
+        right = '<a><b foo="bar" skip="different">text</b></a>'
+
+        parser = etree.XMLParser(remove_blank_text=True)
+        left_tree = etree.fromstring(left, parser)
+        right_tree = etree.fromstring(right, parser)
+        differ = IgnoringDiffer()
+        differ.set_trees(left_tree, right_tree)
+        editscript = list(differ.diff())
+        self.assertEqual(editscript, [])
diff --git a/xmldiff/diff.py b/xmldiff/diff.py
index 5648c26..a30a3fd 100644
--- a/xmldiff/diff.py
+++ b/xmldiff/diff.py
@@ -186,7 +186,7 @@ def node_text(self, node):
         texts = node.xpath("text()")
 
         # Then add attributes and values
-        for tag, value in sorted(node.attrib.items()):
+        for tag, value in sorted(self.node_attribs(node).items()):
             if tag[0] == "{":
                 tag = tag.split("}",)[-1]
             texts.append(f"{tag}:{value}")
@@ -197,6 +197,11 @@ def node_text(self, node):
         self._text_cache[node] = result
         return result
 
+    def node_attribs(self, node):
+        """ Return a dict of attributes to consider for this node.
+        """
+        return node.attrib
+
     def leaf_ratio(self, left, right):
         # How similar two nodes are, with no consideration of their children
         # We use a simple ratio here, I tried Levenshtein distances
@@ -235,8 +240,8 @@ def update_node_attr(self, left, right):
 
         # Update: Look for differences in attributes
 
-        left_keys = set(left.attrib.keys())
-        right_keys = set(right.attrib.keys())
+        left_keys = set(self.node_attribs(left).keys())
+        right_keys = set(self.node_attribs(right).keys())
         new_keys = right_keys.difference(left_keys)
         removed_keys = left_keys.difference(right_keys)
         common_keys = left_keys.intersection(right_keys)

From 155a3bcbfd5d8b191366afc1eec4e08489352eee Mon Sep 17 00:00:00 2001
From: Greg Kempe <greg@kempe.net>
Date: Fri, 23 Oct 2020 10:22:10 +0200
Subject: [PATCH 2/3] Make black happy for contributed code

---
 xmldiff/diff.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/xmldiff/diff.py b/xmldiff/diff.py
index a30a3fd..a9b33a7 100644
--- a/xmldiff/diff.py
+++ b/xmldiff/diff.py
@@ -198,8 +198,7 @@ def node_text(self, node):
         return result
 
     def node_attribs(self, node):
-        """ Return a dict of attributes to consider for this node.
-        """
+        """Return a dict of attributes to consider for this node."""
         return node.attrib
 
     def leaf_ratio(self, left, right):

From 5a7cc0d44e60c698e1f6cddf3f56e564d38c3e7b Mon Sep 17 00:00:00 2001
From: Greg Kempe <greg@kempe.net>
Date: Mon, 26 Oct 2020 16:29:00 +0200
Subject: [PATCH 3/3] Update contributors list

---
 README.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/README.rst b/README.rst
index 5395a9d..df9203a 100644
--- a/README.rst
+++ b/README.rst
@@ -84,5 +84,7 @@ Contributors
 
  * Albertas Agejevas, alga@shoobx.com
 
+ * Greg Kempe, greg@laws.africa
+
 The diff algorithm is based on "`Change Detection in Hierarchically Structured Information <http://ilpubs.stanford.edu/115/1/1995-46.pdf>`_",
 and the text diff is using Google's ``diff_match_patch`` algorithm.