On Thu, Mar 4, 2021 at 1:38 AM Glenn Linderman <v+pyt...@g.nevcal.com>
wrote:
> On 3/3/2021 2:49 PM, Irit Katriel via Python-Dev wrote:
>
> That's an interesting idea.
>
> Do you mean that one exception gets handled and the rest of the group is
> reraised? Or discarded?
>
> The value of sys.exc_info() (and the e in "except T as e:") needs to be a
> single naked exception. So if there is more than one match in the group we
> would need to pick one (let's say the first in DFS order).
>
> If we do this, then we have this situation. Before ExceptionGroups, you
> got to choose which of the exceptions you have is the most important, and
> you raised only that one. Now you raise a bunch of them and the order of
> the except clauses in caller's code determines which one of them counts and
> which ones are discarded. What do you make of that?
>
>
> You _could_ implement it as you said, but remember, you that with this
> idea, you are changing how except clauses workâso instead of making the
> order of the except clauses determine which one counts most, you could
> instead do something else.
>
> One alternative idea would be to take the "first in DFS order" and see if
> it matches any of the except clauses, and if so, process that one. If not,
> then pick the next, and see if it matches, until one is found that matches,
> and can be processed.
>
Or we could make it explicit:
add an optional arg to ExceptionGroup like
ExceptionGroup("eg", list_of_exceptions, singleton=None)
In the example of atexit, where currently it raises only the last exception
from your callbacks, it will instead raise
ExceptionGroup("atexit errors", all_exceptions, singleton=last_exception)
Then except* works as before, ignoring the singleton. But except matches
the singleton.
And there's no magic where you can be surprised about which exception
except chose to look at.
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