In howto/twisted-templates.html listings/element_2.py example doesn't work with FilePath

[lewq]

from twisted.web.template import Element, renderer, XMLFile, tags
from twisted.python.filepath import FilePath

class ExampleElement(Element):
    loader = XMLFile(FilePath('template-1.xml'))

Causes:

Jumping into debugger for post-mortem of exception 'Exception while flattening:
  <ExampleElement object at 0x1b03090>
  File "/usr/local/lib/python2.7/dist-packages/Twisted-12.0.0-py2.7-linux-x86_64.egg/twisted/web/_flatten.py", line 218, in _flattenTree
    element = stack[-1].next()
  File "/usr/local/lib/python2.7/dist-packages/Twisted-12.0.0-py2.7-linux-x86_64.egg/twisted/web/_flatten.py", line 189, in _flattenElement
    result = root.render(request)
  File "/usr/local/lib/python2.7/dist-packages/Twisted-12.0.0-py2.7-linux-x86_64.egg/twisted/web/_element.py", line 184, in render
    return loader.load()
  File "/usr/local/lib/python2.7/dist-packages/Twisted-12.0.0-py2.7-linux-x86_64.egg/twisted/web/template.py", line 397, in load
    self._loadedTemplate = self._loadDoc()
  File "/usr/local/lib/python2.7/dist-packages/Twisted-12.0.0-py2.7-linux-x86_64.egg/twisted/web/template.py", line 388, in <lambda>
    self._loadDoc = lambda: _flatsaxParse(fobj)
  File "/usr/local/lib/python2.7/dist-packages/Twisted-12.0.0-py2.7-linux-x86_64.egg/twisted/web/template.py", line 335, in _flatsaxParse
    parser.parse(fl)
  File "/usr/lib/python2.7/xml/sax/expatreader.py", line 102, in parse
    source = saxutils.prepare_input_source(source)
  File "/usr/lib/python2.7/xml/sax/saxutils.py", line 295, in prepare_input_source
    if source.getByteStream() is None:
AttributeError: FilePath instance has no attribute 'getByteStream'

However replacing FilePath with open so that XMLFile is just operating on a file-like object fixes it. Is this the correct fix for the docs?

[thijs]

Fixing ticket markup.

[rwall]

Thanks for the bug report.

I think the problem is that you are using an older version of Twisted.

In r33940 XMLFile was updated to accept a FilePath. Passing it a file or string is now deprecated.

You can try the 12.0.0 documentation or you could update to the current Twisted release.

•  https://twistedmatrix.com/documents/12.0.0/web/howto/twisted-templates.html

We should probably provide clearer links to the version specific documentation - maybe in footer of the documents themselves.

[exarkun]

To be clear, this is a 12.1.0 feature.