BaseException.message has been deprecated as of Python 2.6

[Jun Omae]

If non-TRAC_ADMIN user requests with hdfdump=1 parameter and Python 2.6 is used, Python says DeprecationWarning.

python trac/web/standalone.py  -p 3000 -a '*,/home/jun66j5/src/trac-htdigest.txt,auth'  /dev/shm/testenv
Server starting in PID 19162.
Serving on 0.0.0.0:3000 view at http://127.0.0.1:3000/
Using HTTP/1.1 protocol version
/home/jun66j5/src/tracdev/git/trac/web/api.py:137: DeprecationWarning: BaseException.message has been deprecated as of Python 2.6
  self.detail = detail.message
192.168.11.11 - - [19/Dec/2014 13:03:40] "GET /testenv?hdfdump=1 HTTP/1.1" 403 -
192.168.11.11 - - [19/Dec/2014 13:03:40] "GET /testenv/chrome/site/your_project_logo.png HTTP/1.1" 404 -
192.168.11.11 - - [19/Dec/2014 13:03:40] "GET /testenv/chrome/site/your_project_logo.png HTTP/1.1" 404 -

[Ryan J Ollos]

Some of the comments in #11286 might be applicable.

[Ryan J Ollos]

While working on #11286 I remember seeing the following behavior: DeprecationWarning with Python 2.6, but not with Python 2.7.

(py2.6)user@ubuntu:~/Workspace/t11944$ python
Python 2.6.9 (default, Jan 25 2014, 21:02:08) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> e = Exception("the message")
>>> e.message
__main__:1: DeprecationWarning: BaseException.message has been deprecated as of Python 2.6
'the message'
>>> dir(e)
['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__getitem__', '__getslice__', '__hash__', '__init__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setstate__', '__sizeof__', '__str__', '__subclasshook__', '__unicode__', 'args', 'message']

Python 2.7.6 (default, Mar 22 2014, 22:59:56) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> e = Exception("the exception")
>>> e.message
'the exception'
>>> dir(e)
['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__getitem__', '__getslice__', '__hash__', '__init__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setstate__', '__sizeof__', '__str__', '__subclasshook__', '__unicode__', 'args', 'message']

I thought I had found an explanation for that somewhere on Stack Overflow, but I'm unable to find it now. Anyway, ​PEP:0352 claims the message attribute was removed in Python 3.0, and I can confirm it is gone at least in 3.4.

Python 3.4.0 (default, Apr 11 2014, 13:05:11) 
[GCC 4.8.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> e = Exception("the exception")
>>> dir(e)
['__cause__', '__class__', '__context__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setstate__', '__sizeof__', '__str__', '__subclasshook__', '__suppress_context__', '__traceback__', 'args', 'with_traceback']

So it seems good to remove the message property from the TracError class for consistency. I did some work on that last weekend while I was offline that I'll post here soon for review.

[Ryan J Ollos]

Replying to rjollos:

So it seems good to remove the message property from the TracError class for consistency. I did some work on that last weekend while I was offline that I'll post here soon for review.

Proposed changes in log:rjollos.git:t11886.

[Ryan J Ollos]

Replying to jomae:

If non-TRAC_ADMIN user requests with hdfdump=1 parameter and Python 2.6 is used, Python says DeprecationWarning.

It looks like that's probably a PermissionError. Another way to avoid the deprecation warning would be to define the message property like the TracError class: tags/trac-1.0.2/trac/core.py@:48-49#L30​.

The Error class in ConfigParser.py has the following code:

# exception classes
class Error(Exception):
    """Base class for ConfigParser exceptions."""

    def _get_message(self):
        """Getter for 'message'; needed only to override deprecation in
        BaseException."""
        return self.__message

    def _set_message(self, value):
        """Setter for 'message'; needed only to override deprecation in
        BaseException."""
        self.__message = value

    # BaseException.message has been deprecated since Python 2.6.  To prevent
    # DeprecationWarning from popping up over this pre-existing attribute, use
    # a new property that takes lookup precedence.
    message = property(_get_message, _set_message)

In light of those hints, I may rework the proposed changes.

[Ryan J Ollos]

It seems to come down to:

1. Deprecate message property of TracError and HTTPException and remove uses of message in the codebase.

or

2. Add message property to the PermissionError` class.

I'm slightly in favor of (1), for consistency with the BaseException class in Python 3. Any suggestions?

[Jun Omae]

I'm slightly in favor of (1), for consistency with the BaseException class in Python 3. Any suggestions?

+1 for (2).

We could remove uses of message in Trac core. I think we should do. However, we cannot remove uses in all plugins. Therefore, I think we should add message property to prevent the warnings.

[Ryan J Ollos]

Replying to jomae:

We could remove uses of message in Trac core.

Done in [13749:13750].

I think we should do. However, we cannot remove uses in all plugins. Therefore, I think we should add message property to prevent the warnings.

Additional proposed changes in log:rjollos.git:t11886.2 and log:rjollos.git:t11886.2-trunk.

[Ryan J Ollos]

OT: the variable name hdfdump might not make much sense now that ClearSilver is removed. Maybe we should add an alias, such as datadump? This came to mind while reading TracTroubleshooting#ClearsilversHDF.

[Jun Omae]

Additional proposed changes in log:rjollos.git:t11886.2 and log:rjollos.git:t11886.2-trunk.

Looks good to me.

[Jun Omae]

OT: the variable name hdfdump might not make much sense now that ClearSilver is removed. Maybe we should add an alias, such as datadump? This came to mind while reading TracTroubleshooting#ClearsilversHDF.

IMO, I'd like to leave with no changes. I don't think it would be good to add a magic token even if it makes much sense. If an alias is added, I like such as __datadump which it rarely conflicts with tokens from Trac core and other plugins.

[Ryan J Ollos]

Committed to 1.0-stable in [13769,13771], merged to trunk in [13770,13772,13774]. Additional change on trunk in [13773].