Using Patcher with py.test

[mirosval]

I have run into an issue using Patcher with py.test.

The issue is that when the code under test throws, the exception bubbles up to py.test, which will then fail processing it, because os.path is patched.

This then results into a horrible mess of tracebacks and exceptions during handling of other exceptions and the original exception is lost, so it makes debugging the underlying problem difficult.

Example:

patcher = Patcher()
patcher.setUp()
foo()  # throws
patcher.tearDown()

I fixed this by wrapping Patcher in a context manager like so:

class ManagedPatcher(Patcher):
        def __enter__(self):
            self.setUp()

        def __exit__(self, exc_type, exc_val, exc_tb):
            self.tearDown()

with ManagedPatcher():
    foo()

This ensures that when an exception is thrown, the patch is unapplied on exit from the context block and the exception is allowed to correctly bubble up and be caught by py.test.

I would suggest adding the two context methods to the original Patcher. I could make a PR for this if you like.

[mrbean-bremen]

Thanks - this sounds good! A context manager for Patcher certainly makes sense in this context. I may add this tomorrow - as it's a small addition, I think a PR is not really needed.

[mirosval]

Oh fantastic, I was hoping you'd say that. ;)

On Thu, Nov 17, 2016 at 9:53 PM mrbean-bremen [email protected]
wrote:

Thanks - this sounds good! A context manager for Patcher certainly makes
sense in this context. I may add this tomorrow - as it's a small addition,
I think a PR is not really needed.

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Best Regards,
Miroslav Zoricak

[mrbean-bremen]

Neither I nor @jmcgeheeiv have much experience with pytest, so we are always glad to get input from pytest users. Thanks for the contribution!
Please check if this is ok for you and close the issue in this case.

[mirosval]

Yes, this is exactly what I did on my side. Perfect! Thank you so much!