Duplicate "except" branch

[pylint-bot]

Originally reported by: Steven Myint (BitBucket: myint, GitHub: @myint?)

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I wonder if it would be useful for Pylint to detect duplicate except branches. For example, I ran into something like this today:

def main():
    try:
        # ...
        pass
    except ValueError:
        # ...
        pass
    except ValueError:
        # We will never get here since it will be caught above.
        # ...
        pass

Thanks

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• Bitbucket: https://bitbucket.org/logilab/pylint/issue/485

[pylint-bot]

Original comment by Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore):

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Yes, it's possible. Would you like to work on a patch?

[pylint-bot]

Original comment by Steven Myint (BitBucket: myint, GitHub: @myint?):

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I haven't written a checker before, but I'll see what I can do. I'm guessing I should start by looking at exceptions.py.

[pylint-bot]

Original comment by Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore):

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Yes. If you need any help, feel free to ask, either here or you can find me on IRC on freenode, #pylint.

[pylint-bot]

Original comment by Steven Myint (BitBucket: myint, GitHub: @myint?):

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Given that setup.py uses 2to3, I guess development must be done under Python 2.7.

One thing I noticed after setting up a Python 2 virtualenv and running python setup.py develop is that I can't run pylint while being in the pylint repository directory. If I do that, I get no output other than a report showing a score of 10. If I change to an unrelated directory, pylint gives the normal output.

[pylint-bot]

Original comment by Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore):

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Nope, 2to3 is used only for converting the tests, the rest works under both versions. Hm, didn't know about the problem you're experiencing, I'll have a look.

[pylint-bot]

Original comment by Steven Myint (BitBucket: myint, GitHub: @myint?):

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Actually, the in-pylint-directory problem happens even without virtualenv. It happens with my normally-installed pylint. And it gives some irrelevant warning messages instead:

myint@macpro:~/projects/pylint
$ pylint --report=no setup.py
Warning: option include-ids is deprecated and ignored.
Warning: option symbols is deprecated and ignored.

(By the way, the associated pull request for this issue is pull request #237.)

[pylint-bot]

Original comment by Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore):

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Could you report another issue for that, please? I'll have a look at the pull request later today.

[pylint-bot]

Original comment by Steven Myint (BitBucket: myint, GitHub: @myint?):

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Sure. See issue #494.

[pylint-bot]

Original comment by Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore):

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Add "duplicate-except" checker

It checks if an exception type was already caught previously in the same
try/except. This fixes #485.

[pylint-bot]

Original comment by Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore):

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Thank you!