On 28.11.2016 22:26, Paul Moore wrote:
On 28 November 2016 at 21:11, Ethan Furman <ethan@stoneleaf.us> wrote:
One "successful" use-case that would be impacted is the fallback import idiom:
try: # this would do two full searches before getting the error import BlahBlah except ImportError: import blahblah
Under this proposal, the above idiom could potentially now fail. If there's a BlahBlah.missing.py, then that will get executed rather than an ImportError being raised, so the fallback wouldn't be executed. This could actually be a serious issue for code that currently protects against optional stdlib modules not being available like this. There's no guarantee that I can see that a .missing.py file would raise ImportError (even if we said that was the intended behaviour, there's nothing to enforce it).
Could the proposal execute the .missing.py file and then raise ImportError? I could imagine that having problems of its own, though...
How about addressing both concerns by triggering the search for .missing.py only if an ImportError bubbles up uncaught (a bit similar to StopIteration nowadays)? Wolfgang