xml.dom.minidom wrong indentation writing for CDATA section

[vsurjaninov]

BPO	36407
Nosy	@scoder, @serhiy-storchaka, @vsurjaninov
PRs	bpo-36407: Fix writing indentations of CDATA section (xml.dom.minidom) #12514 [2.7] bpo-36407: Fix writing indentations of CDATA section (xml.dom.minidom). (GH-12514) #12578

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

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2019-03-27.12:08:27.988>
created_at = <Date 2019-03-23.15:38:49.094>
labels = ['expert-XML', 'type-feature', '3.8']
title = 'xml.dom.minidom wrong indentation writing for CDATA section'
updated_at = <Date 2019-03-27.12:08:27.987>
user = 'https://github.com/vsurjaninov'

bugs.python.org fields:

activity = <Date 2019-03-27.12:08:27.987>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2019-03-27.12:08:27.988>
closer = 'serhiy.storchaka'
components = ['XML']
creation = <Date 2019-03-23.15:38:49.094>
creator = 'vsurjaninov'
dependencies = []
files = []
hgrepos = []
issue_num = 36407
keywords = ['patch']
message_count = 5.0
messages = ['338681', '338701', '338936', '338939', '338943']
nosy_count = 4.0
nosy_names = ['scoder', 'eli.bendersky', 'serhiy.storchaka', 'vsurjaninov']
pr_nums = ['12514', '12578']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue36407'
versions = ['Python 3.8']

[vsurjaninov]

If we are writing xml with CDATA section and leaving non-empty indentation and new-line parameters, a parent node of the section will contain useless indentation, that will be parsed as a text.

Example:

>>doc = minidom.Document()
>>root = doc.createElement('root')
>>doc.appendChild(root)
>>node = doc.createElement('node')
>>root.appendChild(node)
>>data = doc.createCDATASection('</data>')
>>node.appendChild(data)
>>print(doc.toprettyxml(indent=‘ ‘ * 4)
<?xml version="1.0" ?>
<root>
<node>
<![CDATA[</data>]]> </node>
</root>

If we try to parse this output doc, we won’t get CDATA value correctly.

Following code returns a string that contains only indentation characters:

>>doc = minidom.parseString(xml_text)
>>doc.getElementsByTagName('node')[0].firstChild.nodeValue

Returns a string with CDATA value and indentation characters:

>>doc.getElementsByTagName('node')[0].firstChild.wholeText

But we have a workaround:

>>data.nodeType = data.TEXT_NODE
…
>>print(doc.toprettyxml(indent=‘ ‘ * 4)
<?xml version="1.0" ?>
<root>
<node><![CDATA[</data>]]></node>
</root>

It will be parsed correctly:

>>doc.getElementsByTagName('node')[0].firstChild.nodeValue
</data>

But I think it will be better if we fix the writing function, which would set this as default behavior.

[scoder]

Yes, this case is incorrect. Pretty printing should not change character content inside of a simple tag.

The PR looks good to me.

[serhiy-storchaka]

New changeset 384b81d by Serhiy Storchaka (Vladimir Surjaninov) in branch 'master':
bpo-36407: Fix writing indentations of CDATA section (xml.dom.minidom). (GH-12514)
384b81d

[serhiy-storchaka]

Should we backport this change? I am not sure.

[scoder]

I don't think this should be backported. Pretty-printing is not a production relevant feature, more of a "debugging, diffing and help users see what they get" kind of feature. It's good to have it fixed for the future, but we shouldn't bother users with it during a point release.