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Boolean HTML attribute behavior under >3.8.0 #381

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mcdonc opened this issue Aug 25, 2023 · 2 comments
Closed

Boolean HTML attribute behavior under >3.8.0 #381

mcdonc opened this issue Aug 25, 2023 · 2 comments

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@mcdonc
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mcdonc commented Aug 25, 2023 •
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I have been tasked with trying to figure out why templates rendered using Chameleon < 3.8.0 render differently semantically than templates rendered under 3.8.0 and greater.

I was pointed at Pylons/pyramid_chameleon#31 which sorta.. kinda? describes the problem, but not fully. The diagnosis reached within that issue was for pyramid_chameleon to use a boolean_attributes argument to PageTemplate but I am afraid to report that this doesn't actually solve the problem.

The issue is with (braindead) HTML attributes which can valueless like "checked", "selected", etc, and whose mere presence indicates that they are true (their value is ignored).

Below I'm going to repeat the findings I came up with in Pylons/pyramid_chameleon#31 (comment) which explain the problem in depth. TLDR: when boolean_attributes is used, rendering one of those braindead attributes works properly when it is replaced using tal:attributes but not when it is replaced using squiggly brace syntax. If someone can point me at the code that I might should change in Chameleon to fix this, I would be grateful, because this behavior change causes fifteen years of templates to need to be reviewed and changed, which is too much work to ponder.

Anyway....

Here's a program that renders several templates. Some should be detected as
HTML by Chameleon, some as XML, and their output should probably differ based
on whether Chameleon believes they are HTML or XML (spoiler alert: they don't).
Each uses the tal:attribute spelling and the inline curly brace spelling to
replace a checked attribute.

from chameleon import PageTemplate

boolean_attributes= [
        # From http://www.w3.org/TR/xhtml1/#guidelines (C.10)
        "compact",
        "nowrap",
        "ismap",
        "declare",
        "noshade",
        "checked",
        "disabled",
        "readonly",
        "multiple",
        "selected",
        "noresize",
        "defer",
    ]

booleans_html5 = """<!DOCTYPE html>
<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" tal:attributes="checked checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="${checked}"/>
  </form>
</body>
</html>
"""

booleans_htmlfrag = """<form>
  <!-- tal:attributes="checked checked"-->
  <input type="checkbox" tal:attributes="checked checked"/>
  <!-- checked="$\{checked}"-->
  <input type="checkbox" selected="${checked}"/>
</form>
"""

booleans_nodoctype = """<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" tal:attributes="checked checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="${checked}"/>
  </form>
</body>
</html>
"""

booleans_xhtml = """<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" tal="">
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" tal:attributes="checked checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="${checked}"/>
  </form>
</body>
</html>
"""

booleans_xml = """<?xml version="1.0" ?>
<!-- tal:attributes="checked checked"-->
<input type="checkbox" tal:attributes="checked checked" />
<!-- checked="$\{checked}"-->
<input type="checkbox" checked="${checked}" />
"""

for name in (
    "booleans_html5",
    "booleans_htmlfrag",
    "booleans_nodoctype",
    "booleans_xhtml",
    "booleans_xml",
    ):
    inputstr = locals()[name]
    template = PageTemplate(inputstr, boolean_attributes=boolean_attributes)
    print('------------------------------------------------')
    print(name)
    print('------------------------------------------------')
    print(inputstr)
    print()
    print('---checked=True----')
    print(template(checked=True))
    print('---checked=False---')
    print(template(checked=False))
    print()

Here's the output of that program using Chameleon 3.7.4:

------------------------------------------------
booleans_html5
------------------------------------------------
<!DOCTYPE html>
<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" tal:attributes="checked checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="${checked}"/>
  </form>
</body>
</html>


---checked=True----
<!DOCTYPE html>
<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" checked="checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="True"/>
  </form>
</body>
</html>

---checked=False---
<!DOCTYPE html>
<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox"/>

</form>
</body>
</html>


------------------------------------------------
booleans_htmlfrag
------------------------------------------------
<form>
  <!-- tal:attributes="checked checked"-->
  <input type="checkbox" tal:attributes="checked checked"/>
  <!-- checked="$\{checked}"-->
  <input type="checkbox" selected="${checked}"/>
</form>


---checked=True----
<form>
  <!-- tal:attributes="checked checked"-->
  <input type="checkbox" checked="checked"/>
  <!-- checked="$\{checked}"-->
  <input type="checkbox" selected="True"/>
</form>

---checked=False---
<form>
  <!-- tal:attributes="checked checked"-->
  <input type="checkbox"/>
  <!-- checked="$\{checked}"-->
  <input type="checkbox"/>
</form>


------------------------------------------------
booleans_nodoctype
------------------------------------------------
<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" tal:attributes="checked checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="${checked}"/>
  </form>
</body>
</html>


---checked=True----
<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" checked="checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="True"/>
  </form>
</body>
</html>

---checked=False---
<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox"/>
  </form>
</body>
</html>


------------------------------------------------
booleans_xhtml
------------------------------------------------
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" tal="">
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" tal:attributes="checked checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="${checked}"/>
  </form>
</body>
</html>


---checked=True----
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" tal="">
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" checked="checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="True"/>
  </form>
</body>
</html>

---checked=False---
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" tal="">
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox"/>
  </form>
</body>
</html>


------------------------------------------------
booleans_xml
------------------------------------------------
<?xml version="1.0" ?>
<!-- tal:attributes="checked checked"-->
<input type="checkbox" tal:attributes="checked checked" />
<!-- checked="$\{checked}"-->
<input type="checkbox" checked="${checked}" />


---checked=True----
<?xml version="1.0" ?>
<!-- tal:attributes="checked checked"-->
<input type="checkbox" checked="checked" />
<!-- checked="$\{checked}"-->
<input type="checkbox" checked="True" />

---checked=False---
<?xml version="1.0" ?>
<!-- tal:attributes="checked checked"-->
<input type="checkbox" />
<!-- checked="$\{checked}"-->
<input type="checkbox" />

Here's the output of the same program under Chameleon 3.8.0:

------------------------------------------------
booleans_html5
------------------------------------------------
<!DOCTYPE html>
<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" tal:attributes="checked checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="${checked}"/>
  </form>
</body>
</html>


---checked=True----
<!DOCTYPE html>
<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" checked="checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="True"/>
  </form>
</body>
</html>

---checked=False---
<!DOCTYPE html>
<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="False"/>
  </form>
</body>
</html>


------------------------------------------------
booleans_htmlfrag
------------------------------------------------
<form>
  <!-- tal:attributes="checked checked"-->
  <input type="checkbox" tal:attributes="checked checked"/>
  <!-- checked="$\{checked}"-->
  <input type="checkbox" selected="${checked}"/>
</form>


---checked=True----
<form>
  <!-- tal:attributes="checked checked"-->
  <input type="checkbox" checked="checked"/>
  <!-- checked="$\{checked}"-->
  <input type="checkbox" selected="True"/>
</form>

---checked=False---
<form>
  <!-- tal:attributes="checked checked"-->
  <input type="checkbox"/>
  <!-- checked="$\{checked}"-->
  <input type="checkbox" selected="False"/>
</form>


------------------------------------------------
booleans_nodoctype
------------------------------------------------
<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" tal:attributes="checked checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="${checked}"/>
  </form>
</body>
</html>


---checked=True----
<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" checked="checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="True"/>
  </form>
</body>
</html>

---checked=False---
<html>
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="False"/>
  </form>
</body>
</html>


------------------------------------------------
booleans_xhtml
------------------------------------------------
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" tal="">
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" tal:attributes="checked checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="${checked}"/>
  </form>
</body>
</html>


---checked=True----
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" tal="">
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox" checked="checked"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="True"/>
  </form>
</body>
</html>

---checked=False---
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" tal="">
<head>
  <title>Title of document</title>
</head>
<body>
  <form>
    <!-- tal:attributes="checked checked"-->
    <input type="checkbox"/>
    <!-- checked="$\{checked}"-->
    <input type="checkbox" checked="False"/>
  </form>
</body>
</html>


------------------------------------------------
booleans_xml
------------------------------------------------
<?xml version="1.0" ?>
<!-- tal:attributes="checked checked"-->
<input type="checkbox" tal:attributes="checked checked" />
<!-- checked="$\{checked}"-->
<input type="checkbox" checked="${checked}" />


---checked=True----
<?xml version="1.0" ?>
<!-- tal:attributes="checked checked"-->
<input type="checkbox" checked="checked" />
<!-- checked="$\{checked}"-->
<input type="checkbox" checked="True" />

---checked=False---
<?xml version="1.0" ?>
<!-- tal:attributes="checked checked"-->
<input type="checkbox" />
<!-- checked="$\{checked}"-->
<input type="checkbox" checked="False" />

Note that under 3.7.4 when "checked" is False, the checked attribute is
left off the element, even under the XML case (where it presumably should not
be), no matter whether we use tal:attributes or a curly brace statement to
represent "checked".

Under 3.8 (and master), the "checked" attribute is only left off when we use tal:attributes.
@malthe
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malthe commented Aug 26, 2023

I have started a branch here, currently with a failing test:

https://github.com/malthe/chameleon/tree/issue-381-boolean-attributes

The failed tests show that the following fails to take boolean_attributes into account:

  • Dynamic attributes (i.e., using a dictionary to set attributes dynamically)
  • Using $-syntax for interpolation

In both cases, we just get the rendered boolean value instead of the attribute name.

@malthe malthe mentioned this issue Aug 28, 2023
Merged
@malthe malthe closed this as completed Aug 29, 2023
@mcdonc
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mcdonc commented Aug 29, 2023

Thanks for the work!

I added a comment at #382 (comment) about the empty-string case.

@mcdonc mcdonc mentioned this issue Aug 30, 2023
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