Why exceptions for error handling is so important

[via Digitalmars-d]

On Thursday, 15 January 2015 at 19:37:33 UTC, Marc Schütz wrote:
> Now, for a more generic library, you are right that using 
> exceptions in this way is not a good idea. The crucial 
> difference is IMO that in an MVC framework the application code 
> is the one down the stack, while in many other applications it 
> is further up the stack. Therefore, the use of exceptions 
> (which always propagate upwards) have to be assessed 
> differently.

FWIW, although the framework I use provides exceptions for 
returning HTTP status, I don't use them. I have my own 
super-class request handler that captures everything so that I 
can "reformulate" caught exceptions into something that fits the 
REST api I expose, which have to fit what browser support (like 
IE9)...

The only problem I see is if the "exception type system" lacks an 
ontology that the framework can rely upon.E.g. that a function 
pass the exception on, but mistakenly executes an action because 
it makes a classification mistake. But that is more a problem 
with having an inadequate/unspecified/fuzzy exception 
classification mechanisms...

The language could define an ontology that allows you to express 
"pass through unknown", "not a failure", "no rollback" or similar 
as part of the exception type. Finding the exact right semantics 
is perhaps tricky, but also an area where there is room for 
practical innovation.