Support Chameleon attribute expressions.

[thet]

Fix incorrect splitting of Chameleon attribute expressions which led to broken code.

This HTML <input type="text" ${python: "required" if view.required else ""} /> leads now correctly to:

<input type="text"
       ${python: "required" if view.required else ""}
/>

Note: without this fix it is:

<input ""}=""
        "required"=""
        ${python:=""
        else=""
        if=""
        type="text"
        view.required=""
/>

Note 2: This vix is vibe coded. The previous two PRs are not.

[coveralls]

Coverage is 96.753% — thet/fix-chameleon-expressions into master. No base build found for master.

[ale-rt]

This is broken XML and I think it is not allowed by Chameleon.

It seems to me that you should replace:

${python: "required" if view.required else ""}

with:

required="${python: "required" if view.required else ""}

Am I wrong?

[gforcada]

@ale-rt since HTML5 it is no longer strictly speaking XML anymore 🙃

https://stackoverflow.com/questions/5558502/is-html5-valid-xml and plenty of other examples

[ale-rt]

@ale-rt since HTML5 it is no longer strictly speaking XML anymore 🙃

Thanks for the heads up, but this HTML is not relevant here.
You can even use chameleon to render a markdown document and this is even tested in zpretty:

The point is that chameleon wants a proper XML snippet.
Try putting this in the test_rendering template and load the page.

<h1 ${python: "hidden" if False else ""}>Plone User Interface elements test page</h1>

It breaks with:

2026-05-15 12:42:31,870 ERROR   [Zope.SiteErrorLog:35][waitress-2] PTRuntimeError: http://0.0.0.0:9000/Plone/test_rendering
Traceback (innermost last):
  Module ZPublisher.WSGIPublisher, line 181, in transaction_pubevents
  Module ZPublisher.WSGIPublisher, line 390, in publish_module
  Module ZPublisher.WSGIPublisher, line 284, in publish
  Module ZPublisher.mapply, line 98, in mapply
  Module ZPublisher.WSGIPublisher, line 68, in call_object
  Module Products.CMFPlone.browser.test_rendering, line 11, in __call__
  Module Products.Five.browser.pagetemplatefile, line 127, in __call__
  Module Products.Five.browser.pagetemplatefile, line 59, in __call__
  Module zope.pagetemplate.pagetemplate, line 130, in pt_render
   - Warning: Compilation failed
   - Warning: chameleon.exc.ParseError: Unexpected end tag.

 - String:     "</h1>"
 - Filename:   /home/ale/Code/plone/projects/plonex/.venv/lib/python3.13/site-packages/Products/CMFPlone/browser/templates/test_rendering.pt
 - Location:   (line 25: col 83)
 - Source:     ... er Interface elements test page</h1>

The proper syntax is:

<h1 hidden="${python: 'hidden' if False else None}">Plone User Interface elements test page</h1>

I would say this PR is invalid.