Error reporting fails for some Genshi syntax errors

[Christian Boos]

The initial problem was due to a Genshi syntax error in the template:

<span py:if="$change.ipnr" class="ipnr">(IP: $change.ipnr)</span>

(the "$" in the py:if)

But this failed to be properly reported in error.html. Instead, I got this raw backtrace:

Traceback (most recent call last):
  File "C:\Workspace\src\trac\trunk\trac\web\api.py", line 329, in send_error
    'text/html')
  File "C:\Workspace\src\trac\trunk\trac\web\chrome.py", line 514, in render_template
    return stream.render(method, doctype=doctype)
  File "c:\workspace\src\trac\genshi\trunk\genshi\core.py", line 146, in render
    output = u''.join(list(generator))
  File "c:\workspace\src\trac\genshi\trunk\genshi\output.py", line 203, in __call__
    for kind, data, pos in stream:
  File "c:\workspace\src\trac\genshi\trunk\genshi\output.py", line 489, in __call__
    for kind, data, pos in chain(stream, [(None, None, None)]):
  File "c:\workspace\src\trac\genshi\trunk\genshi\output.py", line 439, in __call__
    for kind, data, pos in stream:
  File "c:\workspace\src\trac\genshi\trunk\genshi\core.py", line 207, in _ensure
    for event in stream:
  File "c:\workspace\src\trac\genshi\trunk\genshi\core.py", line 207, in _ensure
    for event in stream:
  File "C:\Workspace\src\trac\trunk\trac\web\chrome.py", line 534, in _strip_accesskeys
    for kind, data, pos in stream:
  File "c:\workspace\src\trac\genshi\trunk\genshi\core.py", line 207, in _ensure
    for event in stream:
  File "C:\Workspace\src\trac\trunk\trac\web\chrome.py", line 523, in _generate
    for kind, data, pos in stream:
  File "c:\workspace\src\trac\genshi\trunk\genshi\template\markup.py", line 188, in _include
    for event in stream:
  File "c:\workspace\src\trac\genshi\trunk\genshi\template\markup.py", line 256, in _match
    content = list(self._include(content, ctxt))
  File "c:\workspace\src\trac\genshi\trunk\genshi\template\markup.py", line 188, in _include
    for event in stream:
  File "c:\workspace\src\trac\genshi\trunk\genshi\template\markup.py", line 231, in _match
    for event in stream:
  File "c:\workspace\src\trac\genshi\trunk\genshi\template\markup.py", line 220, in _strip
    event = stream.next()
  File "c:\workspace\src\trac\genshi\trunk\genshi\template\core.py", line 320, in _eval
    result = data.evaluate(ctxt)
  File "c:\workspace\src\trac\genshi\trunk\genshi\template\eval.py", line 114, in evaluate
    {'data': data})
  File "C:\Workspace\src\trac\trunk\templates\error.html", line 148, in <Expression u"shorten_line(repr(value))">
    <td><code>${shorten_line(repr(value))}</code></td>
  File "c:\workspace\src\trac\genshi\trunk\genshi\template\directives.py", line 94, in __repr__
    if self.expr is not None:
AttributeError: expr

I already had this kind of error before, but now it's the first time I find an easy and reproducible way to trigger it.

With ​[Genshi 455/trunk].

[Christopher Lenz]

So shouldn't you file this on the Genshi site, then? Or is it specific to the way Trac handles these errors?

[Christian Boos]

I'm not sure actually, I thought you should know ;)

[Christian Boos]

Ok, more precisely, there's this problematic bit in error.html:

<code>${shorten_line(repr(value))}</code>

which already failed in the past for me, quite mysteriously with an unicode error.

I have the impression that the repr here sometimes doesn't work well when value is a directive.

The bug lies probably in Genshi, but it's the special way we use it in Trac that trigger that. So I'm not sure where to start…

[Christopher Lenz]

Okay, that instance should be fixed in ​G:r462, but others are still lurking in the code.

[Christian Boos]

Replying to cboos:

Ok, more precisely, there's this problematic bit in error.html:

<code>${shorten_line(repr(value))}</code>

which already failed in the past for me, quite mysteriously with an unicode error.

Like that:

    <td><code>${shorten_line(repr(value))}</code></td>
UnicodeEncodeError: 'ascii' codec can't encode characters in position 14-15: ordinal not in range(128)

… and this was quite likely due to the value being an object whose __repr__ method was returning an unicode string. This doesn't work anymore with Python 2.5, see #5405.

As the original report was about something that got fixed in Genshi and the other similar issues I had can probably be related to the above problem, I think we can close this ticket now.