tests/test-run-tests.py

interfaces: add the optional `bdiff.xdiffblocks()` method

PyCharm flagged where this was called on the protocol class in `mdiff.py` in the
previous commit, but pytype completely missed it.  PyCharm is correct here, but
I'm committing this separately to highlight this potential problem- some of the
implementations don't implement _all_ of the methods the others do, and there's
not a great way to indicate on a protocol class that a method or attribute is
optional- that's kinda the opposite of what static typing is about.

Making the method an `Optional[Callable]` attribute works here, and keeps both
PyCharm and pytype happy, and the generated `mdiff.pyi` and `modules.pyi` look
reasonable.  We might be getting a little lucky, because the method isn't
invoked directly- it is returned from another method that selects which block
function to use.  Except since it is declared on the protocol class, every
module needs this attribute (in theory, but in practice this doesn't seem to be
checked), so the check for it on the module has to change from `hasattr()` to
`getattr(..., None)`.  We defer defining the optional attrs to the type checking
phase as an extra precaution- that way it isn't an attr with a `None` value at
runtime if someone is still using `hasattr()`.

As to why pytype missed this, I have no clue.  The generated `mdiff.pyi` even
has the global variable typed as `bdiff: intmod.BDiff`, so uses of it really
should comply with what is on the class, protocol class or not.

"""test line matching with some failing examples and some which warn

run-test.t only checks positive matches and can not see warnings
(both by design)
"""

import doctest
import os
import re

# this is hack to make sure no escape characters are inserted into the output
if 'TERM' in os.environ:
    del os.environ['TERM']
run_tests = __import__('run-tests')


def prn(ex):
    m = ex.args[0]
    if isinstance(m, str):
        print(m)
    else:
        print(m.decode('utf-8'))


def lm(expected, output):
    r"""check if output matches expected

    does it generally work?
        >>> lm(b'H*e (glob)\n', b'Here\n')
        True

    fail on bad test data
        >>> try: lm(b'a\n',b'a')
        ... except AssertionError as ex: print(ex)
        missing newline
        >>> try: lm(b'single backslash\n', b'single \backslash\n')
        ... except AssertionError as ex: prn(ex)
        single backslash or unknown char
    """
    assert expected.endswith(b'\n') and output.endswith(
        b'\n'
    ), 'missing newline'
    assert not re.search(
        br'[^ \w\\/\r\n()*?]', expected + output
    ), b'single backslash or unknown char'
    test = run_tests.TTest(b'test-run-test.t', b'.', b'.')
    match, exact = test.linematch(expected, output)
    if isinstance(match, str):
        return 'special: ' + match
    elif isinstance(match, bytes):
        return 'special: ' + match.decode('utf-8')
    else:
        return bool(match)  # do not return match object


def wintests():
    r"""test matching like running on windows

    enable windows matching on any os
        >>> _osaltsep = os.altsep
        >>> os.altsep = True
        >>> _osname = os.name
        >>> os.name = 'nt'
        >>> _old_windows = run_tests.WINDOWS
        >>> run_tests.WINDOWS = True

    valid match on windows
        >>> lm(b'g/a*/d (glob)\n', b'g\\abc/d\n')
        True

    direct matching, glob unnecessary
        >>> lm(b'g/b (glob)\n', b'g/b\n')
        'special: -glob'

    missing glob
        >>> lm(b'/g/c/d/fg\n', b'\\g\\c\\d/fg\n')
        True
        >>> lm(b'/g/c/d/fg\n', b'\\g\\c\\d\\fg\r\n')
        True

    restore os.altsep
        >>> os.altsep = _osaltsep
        >>> os.name = _osname
        >>> run_tests.WINDOWS = _old_windows
    """
    pass


def otherostests():
    r"""test matching like running on non-windows os

    disable windows matching on any os
        >>> _osaltsep = os.altsep
        >>> os.altsep = False
        >>> _osname = os.name
        >>> os.name = 'nt'

    backslash does not match slash
        >>> lm(b'h/a* (glob)\n', b'h\\ab\n')
        False

    direct matching glob can not be recognized
        >>> lm(b'h/b (glob)\n', b'h/b\n')
        True

    missing glob can not not be recognized
        >>> lm(b'/h/c/df/g/\n', b'\\h/c\\df/g\\\n')
        False

    restore os.altsep
        >>> os.altsep = _osaltsep
        >>> os.name = _osname
    """
    pass


if __name__ == '__main__':
    doctest.testmod()