Re: [cgiapp] error handling in callbacks

[Timothy Appnel]

On Nov 2, 2004, at 9:47 PM, Thilo Planz wrote:
For errors that occur in the run_mode itself, CGI::App has much 
improved recently by allowing an error_mode that
can handle the exception.

Unfortunately, this does not cover exceptions before or after the 
run_mode, such as in one of the hooks or callbacks.

Maybe it could be modified to somehow use error_mode here as well.
True in a sense, but there are times (for instance with plugin 
callbacks) where you want to throw/catch an error and log it rather 
then stop all processing. I don't see a special error run mode helping 
much there. I also don't see it being helpful for returning the user to 
an existing runmode with the error message in tow.

Just like HTML templating, exception handling is a topic were everyone 
has his favourite methods and modules, so it is very unlikely that
we can agree on something more elaborate than the plain die().
Ah, but not all pigs are created equal though. ;) HTML::Template is 
clearly the favorite however it can be readily replaced or ignored for 
those who feel differently. Since error handling (in the broadest 
sense) is equally as common in CGI app development and something we all 
must do, it's really a shame that its not more robust then die and eval 
for those who don't really have a preference and would appreciate 
having something more functional.

tim/
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Re: [cgiapp] error handling in callbacks

[Thilo Planz]

Agreed, though I wish CGI::App would provide a means of catching that 
and displaying it to the browser rather then throwing up a 500 error 
and forcing a tail through the server error log.
For errors that occur in the run_mode itself, CGI::App has much 
improved recently by allowing an error_mode that
can handle the exception.

Unfortunately, this does not cover exceptions before or after the 
run_mode, such as in one of the hooks or callbacks.

Maybe it could be modified to somehow use error_mode here as well.
If you can provide some code that uses a cleaner error handling
mechanism we could look at incorporating it.
Ideally though, I would love to see CGI::App implement a scheme like 
this by using Class:ErrorHandler as its base (which gives all objects 
from subclasses the error and errstr methods) and make sure all 
methods return at least a null string unless something has gone wrong.
Just like HTML templating, exception handling is a topic were everyone 
has his favourite methods and modules, so it is very unlikely that
we can agree on something more elaborate than the plain die().

Again, CGI::App has greatly improved recently, in that it no longer 
stringifies the exceptions that your code dies() with, so that if you 
want,
you can throw hashrefs or Class::Exceptions.
In earlier versions, CGI::App would flatten them to strings, but now it 
just passes them through, and you can handle them somewhere else ( for 
example in the error_mode, or your instance script, or a custom run() 
method that wraps around the original one)

Thilo
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