Coverage erroneously reports partial coverage inside except block.

[nedbat]

Originally reported by CleanCut (Bitbucket: CleanCut, GitHub: CleanCut)

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Coverage.py, version 3.5.3
Python 3.3.0 (v3.3.0:bd8afb90ebf2, Sep 29 2012, 01:25:11)
OS X 10.8

I have reproduced a situation where coverage erroneously reports a line as only being partially covered.

Please see the attache 'test.py' which you can use to duplicate the problem. The comments inside of test.py also discuss the issue in more depth.

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• Bitbucket: https://bitbucket.org/ned/coveragepy/issue/212
• This issue had attachments: test.py. See the original issue for details.

[nedbat]

This is test.py:

#!python
#!/usr/bin/env python3

from unittest.mock import MagicMock

class X():
    def a(self):
        raise(Exception('expected'))

    def b(self):
        try:
            while True:
                var = 'somevalue'
                self.a()
        except Exception as e:
            if not (e.args == ('expected',)):
                raise(e)
            q = 1

x = X()

# Covers all of the a() function.
try:
    x.a()
except:
    pass

# Covers mot of the b() function, except "raise(e)", which should result
# in partial coverage of the if statement.
x.b()

# _Ought_ to cover the remainder of the b() function.  It does seem to record
# running "raise(e)" -- but the if statement is still marked as having
# only partial coverage.
x.a = MagicMock(side_effect=Exception('unexpected'))
try:
    x.b()
except:
    pass

# (This same bug may occur in Python 2.x -- I didn't try it there)
#
# To reproduce, first make sure that Python 3.3.0 is installed and the 'python3'
# binary is somewhere in your path.  Then install coverage under python3.
# Substitute the path to your python3 coverage executable for 'coverage3' below.
#
# coverage3 run --branch test.py && coverage3 html
#
# Then open htmlcov/index.html and click on 'test' to see the report.  It shows
# line 15 as portially covered.  But it was covered!
#
# Also, if you add a line outside the "if not" statement on line fifteen, then
# the line that you add is what gets marked as partially covered.
#
# Note that if you remove the 'while True' loop from line 11, then coverage
# reports properly.

[nedbat]

When I try this with coverage 3.7.1, it tells me that the "q = 1" line is partial because it never branches to the "except" line before it, which makes no sense. I'm working on a re-implementation of branch coverage which reports 100% for this file, so it will be fixed when that code is merged in.

[nedbat]

This will be fixed when the ast-branch is merged.

[nedbat]

This is fixed in 44719bd (bb), which will be 4.1