wrong handler supplied to req.add_handler() generates error
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Key: MODPYTHON-98
URL: http://issues.apache.org/jira/browse/MODPYTHON-98
Project: mod_python
Type: Bug
Components: core
Versions: 3.2, 3.1.4
Reporter: Graham Dumpleton
The documentation for req.add_handler() states:
Note: There is no checking being done on the validity of the handler name. If
you pass this function an invalid handler it will simply be ignored.
In other words, get the name of the handler wrong and it is supposed to just
ignore it. This is not actually the case, instead it will generate an exception
when it goes to process the handler:
Mod_python error: "PythonHandler example::handler_3"
Traceback (most recent call last):
File
"/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/site-packages/mod_python/apache.py",
line 291, in HandlerDispatch
arg=req, silent=hlist.silent)
File
"/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/site-packages/mod_python/apache.py",
line 538, in resolve_object
raise AttributeError, s
AttributeError: module '/Users/grahamd/Sites/add_handler/example.py' contains
no 'handler_3'
This can be seen with .htaccess file of:
SetHandler mod_python
PythonAccessHandler example
PythonHandler example::handler_1
PythonDebug On
and example.py file containing:
from mod_python import apache
def accesshandler(req):
apache.log_error("accesshandler")
req.add_handler("PythonHandler","example::handler_3")
return apache.OK
def handler_1(req):
apache.log_error("handler_1")
req.content_type = 'text/plain'
req.write("HELLO")
return apache.OK
def handler_2(req):
apache.log_error("handler_2")
return apache.OK
Either the documentation is wrong and an exception is desired, or more likely
this is an extension of the prior problem with hlist.silent as described as
being a problem in other ways in MODPYTHON-46.
In that case the logic of SILENT/NOTSILENT was the wrong way around and it was
fixed by reversing the definitions of the two. In doing this though, it didn't
cover cases where a "silent" flag is passed to hlist_new() and hlist_append()
in the req_add_handler() function of requestobject.c.
Specfically, there are calls to hlist_new() and hlist_append() in that function:
hlist_append(self->request_rec->pool, self->hlo->head,
handler, dir, 0);
hle = hlist_new(self->request_rec->pool, handler, dir, 0);
hlist_append(self->request_rec->pool, hle, handler, dir, 0);
These should be written as:
hlist_append(self->request_rec->pool, self->hlo->head,
handler, dir, SILENT);
hle = hlist_new(self->request_rec->pool, handler, dir, SILENT);
hlist_append(self->request_rec->pool, hle, handler, dir, SILENT);
If this change were made, the code would then behaves conformant with the
documentation as far as being silent, however it highlights a further issue.
This further issue is that although it is silent when the handler name is
wrong, this results in apache.DECLINED being returned for the handler that
couldn't be found. Because apache.DECLINED is returned, Apache will try and
interpret the URL again and if possible serve up a static file etc.
For the above example code this then means that if "example.py" was used in the
URL, the browser gets back a response of:
HELLOfrom mod_python import apache
def accesshandler(req):
apache.log_error("accesshandler")
req.add_handler("PythonHandler","example::handler_3")
return apache.OK
def handler_1(req):
apache.log_error("handler_1")
req.content_type = 'text/plain'
req.write("HELLO")
return apache.OK
def handler_2(req):
apache.log_error("handler_2")
return apache.OK
That is, the content as returned by handler_1(), followed by the contents of
the example.py file.
If instead the URL wasn't 'example.py' but say 'other.py' with that not
existing, get back:
HELLO
OK
The requested URL /~grahamd/add_handler/foo.py was not found on this server.
Apache/2.0.51 (Unix) mod_python/3.2.5b Python/2.3 Server at localhost Port
8080
In some ways, this behaviour suggests that the behaviour whereby it raised an
exception was probably a better way of handling the situtation anyway. Thus,
maybe the documentation should instead be changed and the code left as is, or
at least the 0 arguments changed to be NOTSLIENT to make it more obvious what
it is doing.
The other option is to change the code to use SILENT, but then document the
strange things that can result if the specified handler doesn't exist.
Comments??????
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