On Sun, Feb 15, 2009 at 10:06 PM, David Nolen <dnolen.li...@gmail.com> wrote:
> I've been attempting to combine error-kit and test-is, but getting the
> relation between assert-expr form in test-is and the handle form in
> error-kit is a bit tricky. Looking at the test-is thrown? example and
> Chouser's error-kit post on the mailing list I tried something like the
> following:
>
> (defmethod assert-expr 'raised? [msg form]
> (let [error-type (second form)
> body (rrest form)]
> `(with-handler
> (do
> ~...@body
> (report :fail ~msg '~form nil))
> (handle {:keys [& rest#]}
> (let [tag# (last rest#)]
> (println "raised!" rest# ~error-type)
> (if (= ~error-type tag#)
> (report :pass ~msg '~form nil)
> (report :fail ~msg '~form nil)))))))
>
> The assert-expr seems OK, but I can't seem to get the error-type tag from
> handle.
>
> So here's the promised feedback on handle Chouser ;)
Thanks! You're a brave man for trying such a thing, when error-kit
has such thin documentation.
I think there are a couple problems. One is your attempt at using &
in a :keys destructuring expression. It amounts to something like:
(let [{:keys [& etc]} {:a 1, :b 2}]
etc)
-> nil
You may want to use {:as err-map#} instead, and then pick out the :tag
from the err-map# later. Or perhaps simply insert the ~error-type
there directly.
Another issue is that what is stored in the err-map's :tag value is
the fully-qualified symbol of the error, not the value of that symbol
(which happens to be the fn used to construct it) which is what your
~error-type would evaluate to. I know it's confusing, but it's how it
had to be, since I need the name and functions don't really have names.
To make things worse, getting the fully-qualified name from the macro
argument, which is likely a symbol with a nil namespace, is a bit of a
trick. error-kit/qualify-sym does this, but it's currently private.
It may make sense to make that public for just the kind of shenanigans
you're trying to pull.
If this has been to dense or sketchy, let me know and I'll see if I
can help you further. This is exactly the kind of thing error-kit
needs to be able to do.
--Chouser
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