Some empty attributes are done wrong

[mauritsvanrees]

See plone/plone.app.z3cform#162 (comment)

[ale-rt]

Uhm, zpretty has a list of boolean attributes:

zpretty/zpretty/attributes.py

Lines 25 to 51 in 293d19c

	_known_boolean_attributes = (
	"allowfullscreen",
	"allowpaymentrequest",
	"async",
	"autofocus",
	"autoplay",
	"checked",
	"controls",
	"default",
	"disabled",
	"formnovalidate",
	"hidden",
	"ismap",
	"itemscope",
	"loop",
	"multiple",
	"muted",
	"nomodule",
	"novalidate",
	"open",
	"playsinline",
	"readonly",
	"required",
	"reversed",
	"selected",
	"truespeed",
	)

I think that the expected behavior is to remove the boolean attribute if the value is empty.

[thet]

Boolean attributes are true when they are present, regardless of their value. But it should be ok to remove the asignment part, like in maurits example.
Also see: https://developer.mozilla.org/en-US/docs/Glossary/Boolean/HTML

[ale-rt]

Yeah, I have been thinking as well about this.
I am kind of prone to close this as won't fix.
I still have no clear idea on what caused the test failure in plone/plone.app.z3cform#162.
I kind of like to have boolean attributes to be rendered valueless.

[mauritsvanrees]

So I guess if you have this in your template, the template works fine:

disabled=""
tal:attributes="disabled python:True"

But then zpretty changes it to this:

disabled
tal:attributes="disabled python:True"

And then zope.pagetemplate or Chameleon or whatever somehow does not know how to apply the tal:attributes anymore. Can that be it? That is my working theory now.

That is not nice, but not really sure where to fix this in code. And it can easily be fixed in the template itself: there is no need to have either disabled or disable="" or disabled="disabled" in there if you are going to replace it with tal:attributes anyway.

I guess it is fine to close this issue.

[ale-rt]

It seems to me that chameleon does not behave properly with boolean attributes:

[ale@flo chameleon]$ cat test.pt
<input required="" tal:attributes="required string:required">
<input required tal:attributes="required string:required">
<input required foo="bar" tal:attributes="required string:required">

[ale@flo chameleon]$ cat test.py
from chameleon import PageTemplate

with open("test.pt") as f:
    print(PageTemplate(f.read())())

[ale@flo chameleon]$ python test.py 
<input required="required">
<input requiredrequired>
<input requiredrequired foo="bar">