ElementTree does not find elements in a default namespace with namespaces

[myronww]

BPO	40104
Nosy	@@myronww

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2020-03-29.19:55:45.681>
created_at = <Date 2020-03-29.19:13:13.542>
labels = ['3.7', '3.8', 'type-bug', 'library', '3.9']
title = 'ElementTree does not find elements in a default namespace with namespaces'
updated_at = <Date 2020-03-29.19:55:45.681>
user = 'https://github.com/myronww'

bugs.python.org fields:

activity = <Date 2020-03-29.19:55:45.681>
actor = 'myronww'
assignee = 'none'
closed = True
closed_date = <Date 2020-03-29.19:55:45.681>
closer = 'myronww'
components = ['Library (Lib)']
creation = <Date 2020-03-29.19:13:13.542>
creator = 'myronww'
dependencies = []
files = []
hgrepos = []
issue_num = 40104
keywords = []
message_count = 2.0
messages = ['365273', '365276']
nosy_count = 1.0
nosy_names = ['myronww']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue40104'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']

[myronww]

When you have an xml document like the one with a default namespace below. When you try to lookup nodes in the document they are not found.

docTree.find("specVersion")
None

If you add a namespaces map with the '' key and the default namespaces like:

{ '': 'urn:schemas-upnp-org:device-1-0' }

then the nodes are still not found. The issue is that there is a case
missing from xpath_tokenizer that does not yield a pair with the default namespace when one is specified. Here is a fix.

myronww@0fc65da

from xml.etree.ElementTree import fromstring as parse_xml_fromstring
from xml.etree.ElementTree import ElementTree

SAMPLEXML = """<?xml version="1.0" encoding="utf-8"?>
<root xmlns="urn:schemas-upnp-org:device-1-0">
    <specVersion><major>1</major><minor>0</minor></specVersion>
    <device>
        <deviceType>urn:schemas-wifialliance-org:device:WFADevice:1</deviceType>
        <friendlyName>R7400 (Wireless AP)</friendlyName>
    </device>
</root>

rootNode = parse_xml_fromstring(SAMPLEXML)
# Create a namespaces map like { '': 'urn:schemas-upnp-org:device-1-0' }
defaultns = {"": docNode.tag.split("}")[0][1:]}

specVerNode = docNode.find("specVersion", namespaces=defaultns)

Results should look like this

docNode.find("specVersion", namespaces=defaultns)
<Element '{urn:schemas-upnp-org:device-1-0}specVersion' at 0x7f18030e32f0>

[myronww]

Looks like this is fixed in the latest source code.