Add Accessor.openText() as context manager for openAddress()

[bernhardkaindl]

The commits on this PR depend on the 1st commit:

It adds Accessor.openText() as a new API to make uses like ConfigParser().read_file(TextIO) which need TextIO(IO[str]). It replaces calls like these (change commit: a97be27?diff=split)

           rawtreeinfofp = access.openAddress(cls.TREEINFO_FILENAME)
            if sys.version_info < (3, 0) or isinstance(rawtreeinfofp, io.TextIOBase):
                # e.g. with FileAccessor
                treeinfofp = rawtreeinfofp
            else:
                # e.g. with HTTPAccessor
                treeinfofp = io.TextIOWrapper(rawtreeinfofp, encoding='utf-8')
            treeinfo = configparser.ConfigParser()
            treeinfo.read_file(treeinfofp)
            if treeinfofp != rawtreeinfofp:
                treeinfofp.close()
            rawtreeinfofp.close()

with:

            with access.openText(cls.TREEINFO_FILENAME) as fp:
                treeinfo.read_file(fp)

It makes it easy to use TextIO(IO[str]) with xcp.accessor on Python3 by using a context manager which takes care of closing all buffers/readers after leaving the context:

• xcp/accessor.py: openText(): Context manager to read text from addr

  Add Accessor.openText() as context manager to wrap openAddress() with io.TextIOWrapper (if needed which is what Yann Dirson did as well in PR Testsuite driven py3 #17/Initial Python3 support with Test-Driven-Development enforced by CI (with git diff coverage and diff lint checking) + mypy, pyre and pytype #27):

  • Accessor.openText():
    • Yields a TextIOWrapper (or instance of IO[str]) or False
    • On leaving the context, closes the created TextIOWrapper and the underlying file

  It is intented for use in xcp.repository and in any other user requiring text as string without having to call .decode() after reading the returned file object.

• xcp/repository.py: Use Accessor.openText() for ConfigParser()

  Use Accessor.openText() in _getVersion() for ConfigParser().read_file().
  It simplifies _getVersion() dramatically and causes Accessor.openText() to be tested with xcp.accessor.FileAccessor and xcp.accessor.HTTPAccessor.

• tests/test_mountingaccessor.py: Test MountingAccessor.openText()

  Test openText() with subclasses of xcp.accessor.MountingAccessor

• tests/test_ftpaccessor.py: Test FTPAccessor.openText()

  New test: Download a text file containing UTF-8 using FTPAccessor.openText() and compare the returned string.

• tests/test_httpaccessor.py: Add test for HTTPAccessor.openText()

  Add test to get text containing UTF-8 using HTTPAccessor.openText() and compare the returned decoded string contents.

• tests/test_httpaccessor.py: Split assert_http_get_request_data()

  Split assert_http_get_request_data() using contextlib.contextmanager

[codecov]

Codecov Report

Merging #76 (eb14ba0) into master (6e930d1) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #76      +/-   ##
==========================================
+ Coverage   77.59%   77.62%   +0.03%     
==========================================
  Files          21       21              
  Lines        3468     3473       +5     
==========================================
+ Hits         2691     2696       +5     
  Misses        777      777              

Flag	Coverage Δ
unittest	77.62% <100.00%> (+0.03%)	⬆️

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Impacted Files	Coverage Δ
xcp/accessor.py	86.83% <100.00%> (+0.63%)	⬆️
xcp/repository.py	74.44% <100.00%> (-0.87%)	⬇️