Babel issue KeyError: 'dgettext'

[clemens]

There seems to be a problem with babel with the ​CcSelectorPlugin. This plugin produces an error message if Babel is not installed. But since this root cause seems to be with the TRAC core, I am submitting the ticket here (and not at the Track-Hacks site).

Plugin error when Babel is not installed

I have been using the CcSelectorPlugin for many years. Now I re-installed my TRAC server (now with TRAC 1.6). Intentionally I decided to install TRAC without Babel because we do not want multi-lingual support.

After installing CcSelectorPlugin (Version 0.3, TrackHacks Revision 18597, from Nov. 2023, installation via PIP) it presents the following error when I click the "CC Selection" button:

Trac detected an internal error:
KeyError: 'dgettext'

The Python Traceback points to site-packages/trac/util/translation.py.

Python Traceback
File "/data/trac/python/lib/python3.11/site-packages/trac/web/main.py", line 609, in dispatch_request dispatcher.dispatch(req)
File "/data/trac/python/lib/python3.11/site-packages/trac/web/main.py", line 301, in dispatch raise e
File "/data/trac/python/lib/python3.11/site-packages/trac/web/main.py", line 265, in dispatch output = chrome.render_template(req, template, data, metadata)
File "/data/trac/python/lib/python3.11/site-packages/trac/web/chrome.py", line 1381, in render_template template, data = self.prepare_template(req, filename, data, text, 
File "/data/trac/python/lib/python3.11/site-packages/trac/web/chrome.py", line 1487, in prepare_template domain_functions = translation.domain_functions(domain, symbols)
File "/data/trac/python/lib/python3.11/site-packages/trac/util/translation.py", line 92, in domain_functions return [_functions[s] for s in symbols]
File "/data/trac/python/lib/python3.11/site-packages/trac/util/translation.py", line 92, in <listcomp> return [_functions[s] for s in symbols] 

Discussion

Of course the solution is to install Babel, which will solve the problem.

Nevertheless IMHO either a plug-in should clearly state its dependencies during installation (or during run-time or in the documentation). Best of course would be would be, if the plug-in could run without Babel. After all, Babel is just optional for TRAC.

Although I am reporting an issue with a plugin this is supposed to be an issue with the TRAC core. This issue was discussed on the TRAC mailing list and I was told to open a ticket here.

[Clemens <c.feige@…>]

I want to contribute some details about my TRAC where I found this issue:

• Trac 1.6 running on Linux
• Babel 2.14.0
• Jinja2 3.1.3
• Python 3.11.2

[Clemens <c.feige@…>]

This is the answer I received from Jun Omae on the mailing list. He already made some experiments and statements which I am quoting here:

QUOTE:

That is an issue of Trac core since 1.4.x. It is reproduced with Trac 1.4.4 and 1.6 without Babel. Please report it to trac.edgewall.org/newticket.

TRAC 1.6:

$ python3.11 -m venv /dev/shm/trac-1.6
$ /dev/shm/trac-1.6/bin/pip install -q Trac~=1.6.0
$ /dev/shm/trac-1.6/bin/python
Python 3.11.8 (main, Feb 25 2024, 16:41:26) [GCC 9.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.

>>> import babel
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'babel'
>>> import trac
>>> trac.__version__
'1.6'
>>> from trac.test import EnvironmentStub, MockRequest
>>> from trac.web.chrome import Chrome
>>> env = EnvironmentStub()
>>> req = MockRequest(env)
>>> chrome = Chrome(env)
>>> chrome.prepare_template(req, 'layout.html', {}, domain='messages')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/dev/shm/trac-1.6/lib/python3.11/site-packages/trac/web/chrome.py", line 1487, in prepare_template
    domain_functions = translation.domain_functions(domain, symbols)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/dev/shm/trac-1.6/lib/python3.11/site-packages/trac/util/translation.py", line 92, in domain_functions
    return [_functions[s] for s in symbols]
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/dev/shm/trac-1.6/lib/python3.11/site-packages/trac/util/translation.py", line 92, in <listcomp>
    return [_functions[s] for s in symbols]
            ~~~~~~~~~~^^^
KeyError: 'dgettext'
>>>

TRAC 1.4:

$ virtualenv -p /usr/bin/python2.7 /dev/shm/trac-1.4
$ /dev/shm/trac-1.4/bin/pip install -q Trac~=1.4.0
$ /dev/shm/trac-1.4/bin/python
Python 2.7.18 (default, Jul  1 2022, 12:27:04)
[GCC 9.4.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import babel
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named babel
>>> import trac
>>> trac.__version__
'1.4.4'
>>> from trac.test import EnvironmentStub, MockRequest
>>> from trac.web.chrome import Chrome
>>> env = EnvironmentStub()
>>> req = MockRequest(env)
>>> chrome = Chrome(env)
>>> chrome.prepare_template(req, 'layout.html', {}, domain='messages')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/dev/shm/trac-1.4/lib/python2.7/site-packages/trac/web/chrome.py", line 1614, in prepare_template
    domain_functions = translation.domain_functions(domain, symbols)
  File "/dev/shm/trac-1.4/lib/python2.7/site-packages/trac/util/translation.py", line 92, in domain_functions
    return [_functions[s] for s in symbols]
KeyError: 'dngettext'
>>>

[Jun Omae]

This issue can be reproduced with/without Babel.

>>> import trac, babel
>>> (trac.__version__, babel.__version__)
('1.6', '2.14.0')
>>> from trac.env import Environment
>>> from trac.test import MockRequest
>>> from trac.web.chrome import Chrome
>>> from trac.util import read_file
>>>
>>> env = Environment('/dev/shm/tracenv-1.6')
>>> req = MockRequest(env)
>>> chrome = Chrome(env)
>>> print(read_file('/dev/shm/tracenv-1.6/templates/test.html'))
${dgettext("messages", "Your changes have been saved.")}

>>> t = chrome.render_template(req, 'test.html', {'data': 42}, {'domain': 'messages', 'iterable': False})
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/dev/shm/trac-1.6/lib/python3.11/site-packages/trac/web/chrome.py", line 1411, in render_template
    return self.generate_template_stream(template, data, text,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/dev/shm/trac-1.6/lib/python3.11/site-packages/trac/web/chrome.py", line 1533, in generate_template_stream
    return b''.join(generate())
           ^^^^^^^^^^^^^^^^^^^^
  File "/dev/shm/trac-1.6/lib/python3.11/site-packages/trac/web/chrome.py", line 1531, in generate
    for chunk in stream:
  File "/dev/shm/trac-1.6/lib/python3.11/site-packages/jinja2/environment.py", line 1662, in __next__
    return self._next()  # type: ignore
           ^^^^^^^^^^^^
  File "/dev/shm/trac-1.6/lib/python3.11/site-packages/jinja2/environment.py", line 1639, in _buffered_generator
    c = next(self._gen)
        ^^^^^^^^^^^^^^^
  File "/dev/shm/trac-1.6/lib/python3.11/site-packages/jinja2/environment.py", line 1354, in generate
    yield self.environment.handle_exception()
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/dev/shm/trac-1.6/lib/python3.11/site-packages/jinja2/environment.py", line 936, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "/dev/shm/tracenv-1.6/templates/test.html", line 1, in top-level template code
    ${dgettext("messages", "Your changes have been saved.")}
    ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/dev/shm/trac-1.6/lib/python3.11/site-packages/trac/util/translation.py", line 295, in <lambda>
    return lambda *args, **kw: _functions[symbol](domain, *args, **kw)
                               ~~~~~~~~~~^^^^^^^^
KeyError: 'dgettext'
>>>

[Dirk Stöcker]

The current version of CCSelectorPlugin from trunk has nowhere "dgettext" in the code. Which means you're using an old version.

Correct plugin for ≥ 1.6 can be found here: ​https://trac-hacks.org/svn/ccselectorplugin/trunk/

I don't think there is anything wrong in core.

[Jun Omae]

Any plugins don't have the root cause. It occurs when process_request returns domain in metadata parameter. Chrome class injects domain functions (_, gettext, dgettext, …) to the template instance on rendering process, however, KeyError is raised.

The issue is absolutely in Trac core.

>>> import babel
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'babel'
>>> from trac.env import Environment
>>> from trac.test import EnvironmentStub, MockRequest
>>> from trac.web.api import IRequestHandler
>>> from trac.core import Component, implements
>>> from trac.web.main import RequestDispatcher
>>>
>>> class Foo(Component):
...   implements(IRequestHandler)
...   def match_request(self, req):
...     return req.path_info == '/test'
...   def process_request(self, req):
...     return 'layout.html', {'data': 42}, {'domain': 'messages'}
...
>>> env = EnvironmentStub()
>>> req = MockRequest(env, path_info='/test')
>>> dispatcher = RequestDispatcher(env)
>>> dispatcher.dispatch(req)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/jun66j5/src/tracdev/git/trac/web/main.py", line 301, in dispatch
    raise e
  File "/home/jun66j5/src/tracdev/git/trac/web/main.py", line 265, in dispatch
    output = chrome.render_template(req, template, data, metadata)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jun66j5/src/tracdev/git/trac/web/chrome.py", line 1381, in render_template
    template, data = self.prepare_template(req, filename, data, text,
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jun66j5/src/tracdev/git/trac/web/chrome.py", line 1487, in prepare_template
    domain_functions = translation.domain_functions(domain, symbols)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jun66j5/src/tracdev/git/trac/util/translation.py", line 92, in domain_functions
    return [_functions[s] for s in symbols]
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jun66j5/src/tracdev/git/trac/util/translation.py", line 92, in <listcomp>
    return [_functions[s] for s in symbols]
            ~~~~~~~~~~^^^
KeyError: 'dgettext'
>>>

[Clemens <c.feige@…>]

Replying to Dirk Stöcker:

The current version of CCSelectorPlugin from trunk has nowhere "dgettext" in the code. Which means you're using an old version.

Correct plugin for ≥ 1.6 can be found here: ​https://trac-hacks.org/svn/ccselectorplugin/trunk/

I don't think there is anything wrong in core.

I am quite sure that I am using the most recent version of the CCSelectorPlugin (Version 0.3, TrackHacks Revision 18597, from Nov. 2023) because I just installed it myself few days ago with this command:

pip install svn+https://trac-hacks.org/svn/ccselectorplugin/trunk/

Yes, you are right, the text dgettextdoes not appear in the plug-in code. This was something I checked when I came across this error, too. I am not sure if this tells us where this root problem is, in the plugin or in the core.

Seems that Jun has found something…

[Jun Omae]

Proposed changes in [bd056f646/jomae.git].

[Jun Omae]

Replying to Clemens <c.feige@…>:

Yes, you are right, the text dgettextdoes not appear in the plug-in code. This was something I checked when I came across this error, too. I am not sure if this tells us where this root problem is, in the plugin or in the core.

That is a defect in Trac core. Work around for the plugin is avoid process_request returning {'domain': 'cc_selector'} as metadata like the following:

cc_selector/cc_selector.py

@@ -77 +77 @@
             'cc_developers': cc_developers,
             'show_fullname': self.show_fullname
         }
-        return 'cc_selector_jinja.html', data, {'domain': 'cc_selector'}
+        return 'cc_selector_jinja.html', data

cc_selector/templates/cc_selector_jinja.html

@@ -1 +1 @@
 # import "macros.html" as jmacros with context
+# set _ = partial(dgettext, 'cc_selector')
 <!DOCTYPE html>
 <html>
   <head>

[Jun Omae]

Added [ac30ba8be/jomae.git] to the proposed changes. The tag_ function is available in Jinja2 template but tagn_, dtgettext and dtngettext are unavailable. The changes allow the latter functions.

[Jun Omae]

Fixed in [17794] and merged in [17795].