[Haskell-cafe] Decorating exceptions with backtrace information

Ben Gamari ben at well-typed.com
Fri May 8 18:03:41 UTC 2020


Henning Thielemann <lemming at henning-thielemann.de> writes:

> On Fri, 8 May 2020, Niklas Hamb├╝chen wrote:
>
>> On 5/8/20 5:37 PM, Henning Thielemann wrote:
>>
>>> a callstack is not useful for a user.
>>
>> Call stacks have been very useful to me as a user of non-Haskell tools 
>> so far, because they are excellent for attaching to bug reports and 
>> usually led to developers fixing my problems faster.
>
> This confirms that they are not for you, but you only forward them to the 
> developer.
>
>
> Can someone please give me examples where current state lacks and how they 
> are addressed by the proposal(s)?

We can debate whether partial functions like `fromJust` should exist; however,
the fact of the matter is that they do exist and they are used.
Furthermore, even `base`'s own IO library (e.g. `openFile`) uses
synchronous exceptions to report errors.

This becomes particularly painful when building large systems:
Even if I am careful to avoid such functions in my own code, as my
dependency footprint grows it becomes more likely that some transitive
dependency will expose a partial interface (perhaps even without my
knowledge). This is a problem that industrial users are all too familiar
with.

Perhaps this helps to shed some light on the motivation?

Cheers,

- Ben
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