On 2017-06-23 23:56, Cameron Simpson wrote:
On 24Jun2017 05:02, Steven D'Aprano <st...@pearwood.info> wrote:
[snip]
I think the concept of a "shallow exception" is ill-defined, and to the
degree that it is defined, it is *dangerous*: a bug magnet waiting to
strike.
What do you mean by "directly raised from the surface code"? Why is
bah[5] "surface code" but foo(x) is not? But call a function (or
method).
[...]
I've replied to Paul Moore and suggested this definition as implementable and
often useful:
A shallow catch would effectively need to mean "the exception's
uppermost traceback frame refers to one of the program lines
in the try/except suite". Which would work well for lists and
other builtin types. And might be insufficient for a duck-type
with python-coded dunder methods.
The target here is not perform magic but to have a useful tool to identify
exceptions that arise fairly directly from the adjacent clode and not what it
calls. Without writing cumbersome and fragile boilerplate to dig into an
exception's traceback.
I think a "shallow exception" would be one that's part of a defined API,
as distinct from one that is an artifact of the implementation, a leak
in the abstraction.
It's like when "raise ... from None" was introduced to help in those
cases where you want to replace an exception that's a detail of the
(current) internal implementation with one that's intended for the user.
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