Explicitly close files

[nedbat]

Originally reported by Brett Cannon (Bitbucket: brettcannon, GitHub: brettcannon)

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There are three places in coverage.py where a file is simply opened and read from in a single line, e.g., open(file_path)read(). While technically valid, it does rely somewhat on CPython semantics of refcounting; other VMs might not close the open file quickly. It also triggers ResourceWarnings in Python 3.2 when run under development settings.

A patch is attached which adds try/finally blocks to explicitly close files.

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• Bitbucket: https://bitbucket.org/ned/coveragepy/issue/104
• This issue had attachments: close_files.diff. See the original issue for details.

[nedbat]

Brett, thanks, I should have known this, having made these very same changes to Cog when porting to Jython. The patch looks great, but I won't get to applying it for a few days...

[nedbat]

Fixed in <<changeset 03498ff6127f (bb)>>, thanks Brett!