From f7a3bd19c7246087a537cbc7530d2fc316bea6fd Mon Sep 17 00:00:00 2001
From: "Felix C. Stegerman" <flx@obfusk.net>
Date: Mon, 26 Oct 2020 15:58:44 +0100
Subject: [PATCH 1/3] bpo-42151: don't set specified_attributes=1 in pure
 Python ElementTree

Make the pure Python implementation of xml.etree.ElementTree behave the
same as the C implementation (_elementree) with regards to default
attribute values (by not setting specified_attributes=1).
---
 Lib/xml/etree/ElementTree.py | 2 --
 1 file changed, 2 deletions(-)

diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py
index 7a269001d6e18f6..168418e466c4522 100644
--- a/Lib/xml/etree/ElementTree.py
+++ b/Lib/xml/etree/ElementTree.py
@@ -1560,7 +1560,6 @@ def __init__(self, *, target=None, encoding=None):
         # Configure pyexpat: buffering, new-style attribute handling.
         parser.buffer_text = 1
         parser.ordered_attributes = 1
-        parser.specified_attributes = 1
         self._doctype = None
         self.entity = {}
         try:
@@ -1580,7 +1579,6 @@ def _setevents(self, events_queue, events_to_report):
         for event_name in events_to_report:
             if event_name == "start":
                 parser.ordered_attributes = 1
-                parser.specified_attributes = 1
                 def handler(tag, attrib_in, event=event_name, append=append,
                             start=self._start):
                     append((event, start(tag, attrib_in)))

From 1739e878d45c60dd37d076bef461b37924139039 Mon Sep 17 00:00:00 2001
From: "Felix C. Stegerman" <flx@obfusk.net>
Date: Mon, 26 Oct 2020 16:17:18 +0100
Subject: [PATCH 2/3] bpo-42151: add ElementTree test for default attribute
 values

---
 Lib/test/test_xml_etree.py | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/Lib/test/test_xml_etree.py b/Lib/test/test_xml_etree.py
index fd4a38527fde066..fcb1f7fdfbbde54 100644
--- a/Lib/test/test_xml_etree.py
+++ b/Lib/test/test_xml_etree.py
@@ -108,6 +108,19 @@
 <document>&entity;</document>
 """
 
+ATTLIST_XML = """\
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE Foo [
+<!ELEMENT foo (bar*)>
+<!ELEMENT bar (#PCDATA)*>
+<!ATTLIST bar xml:lang CDATA "eng">
+<!ENTITY qux "quux">
+]>
+<foo>
+<bar>&qux;</bar>
+</foo>
+"""
+
 def checkwarnings(*filters, quiet=False):
     def decorator(test):
         def newtest(*args, **kwargs):
@@ -1354,6 +1367,12 @@ def test_tree_write_attribute_order(self):
         self.assertEqual(serialize(root, method='html'),
                 '<cirriculum status="public" company="example"></cirriculum>')
 
+    def test_attlist_default(self):
+        # Test default attribute values; See BPO 42151.
+        root = ET.fromstring(ATTLIST_XML)
+        self.assertEqual(root[0].attrib,
+                         {'{http://www.w3.org/XML/1998/namespace}lang': 'eng'})
+
 
 class XMLPullParserTest(unittest.TestCase):
 

From a325328166aa2fee744d4ca08cf77dce2fa142ec Mon Sep 17 00:00:00 2001
From: "Felix C. Stegerman" <flx@obfusk.net>
Date: Mon, 26 Oct 2020 18:01:50 +0100
Subject: [PATCH 3/3] bpo-42151: add NEWS entry

---
 .../next/Library/2020-10-26-18-01-09.bpo-42151.et5f7s.rst      | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2020-10-26-18-01-09.bpo-42151.et5f7s.rst

diff --git a/Misc/NEWS.d/next/Library/2020-10-26-18-01-09.bpo-42151.et5f7s.rst b/Misc/NEWS.d/next/Library/2020-10-26-18-01-09.bpo-42151.et5f7s.rst
new file mode 100644
index 000000000000000..6361f2c088d2df0
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-10-26-18-01-09.bpo-42151.et5f7s.rst
@@ -0,0 +1,3 @@
+Make the pure Python implementation of :mod:`xml.etree.ElementTree` behave
+the same as the C implementation (:mod:`_elementree`) regarding default
+attribute values (by not setting ``specified_attributes=1``).