path: root/tests/helpers.py

# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
# For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt

"""Helpers for coverage.py tests."""

import collections
import contextlib
import glob
import os
import os.path
import re
import subprocess
import textwrap

from unittest import mock

from coverage.misc import output_encoding


def run_command(cmd):
    """Run a command in a sub-process.

    Returns the exit status code and the combined stdout and stderr.

    """
    # In some strange cases (PyPy3 in a virtualenv!?) the stdout encoding of
    # the subprocess is set incorrectly to ascii.  Use an environment variable
    # to force the encoding to be the same as ours.
    sub_env = dict(os.environ)
    sub_env['PYTHONIOENCODING'] = output_encoding()

    proc = subprocess.Popen(
        cmd,
        shell=True,
        env=sub_env,
        stdin=subprocess.PIPE, stdout=subprocess.PIPE,
        stderr=subprocess.STDOUT
        )
    output, _ = proc.communicate()
    status = proc.returncode

    # Get the output, and canonicalize it to strings with newlines.
    if not isinstance(output, str):
        output = output.decode(output_encoding())
    output = output.replace('\r', '')

    return status, output


def make_file(filename, text="", bytes=b"", newline=None):
    """Create a file for testing.

    `filename` is the relative path to the file, including directories if
    desired, which will be created if need be.

    `text` is the content to create in the file, a native string (bytes in
    Python 2, unicode in Python 3), or `bytes` are the bytes to write.

    If `newline` is provided, it is a string that will be used as the line
    endings in the created file, otherwise the line endings are as provided
    in `text`.

    Returns `filename`.

    """
    # pylint: disable=redefined-builtin     # bytes
    if bytes:
        data = bytes
    else:
        text = textwrap.dedent(text)
        if newline:
            text = text.replace("\n", newline)
        data = text.encode('utf8')

    # Make sure the directories are available.
    dirs, _ = os.path.split(filename)
    if dirs and not os.path.exists(dirs):
        os.makedirs(dirs)

    # Create the file.
    with open(filename, 'wb') as f:
        f.write(data)

    return filename


def nice_file(*fparts):
    """Canonicalize the file name composed of the parts in `fparts`."""
    fname = os.path.join(*fparts)
    return os.path.normcase(os.path.abspath(os.path.realpath(fname)))


class CheckUniqueFilenames:
    """Asserts the uniqueness of file names passed to a function."""
    def __init__(self, wrapped):
        self.filenames = set()
        self.wrapped = wrapped

    @classmethod
    def hook(cls, obj, method_name):
        """Replace a method with our checking wrapper.

        The method must take a string as a first argument. That argument
        will be checked for uniqueness across all the calls to this method.

        The values don't have to be file names actually, just strings, but
        we only use it for filename arguments.

        """
        method = getattr(obj, method_name)
        hook = cls(method)
        setattr(obj, method_name, hook.wrapper)
        return hook

    def wrapper(self, filename, *args, **kwargs):
        """The replacement method.  Check that we don't have dupes."""
        assert filename not in self.filenames, (
            f"File name {filename!r} passed to {self.wrapped!r} twice"
            )
        self.filenames.add(filename)
        ret = self.wrapped(filename, *args, **kwargs)
        return ret


def re_lines(text, pat, match=True):
    """Return the text of lines that match `pat` in the string `text`.

    If `match` is false, the selection is inverted: only the non-matching
    lines are included.

    Returns a string, the text of only the selected lines.

    """
    return "".join(l for l in text.splitlines(True) if bool(re.search(pat, l)) == match)


def re_line(text, pat):
    """Return the one line in `text` that matches regex `pat`.

    Raises an AssertionError if more than one, or less than one, line matches.

    """
    lines = re_lines(text, pat).splitlines()
    assert len(lines) == 1
    return lines[0]


def remove_files(*patterns):
    """Remove all files that match any of the patterns."""
    for pattern in patterns:
        for fname in glob.glob(pattern):
            os.remove(fname)


# Map chars to numbers for arcz_to_arcs
_arcz_map = {'.': -1}
_arcz_map.update({c: ord(c) - ord('0') for c in '123456789'})
_arcz_map.update({c: 10 + ord(c) - ord('A') for c in 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'})

def arcz_to_arcs(arcz):
    """Convert a compact textual representation of arcs to a list of pairs.

    The text has space-separated pairs of letters.  Period is -1, 1-9 are
    1-9, A-Z are 10 through 36.  The resulting list is sorted regardless of
    the order of the input pairs.

    ".1 12 2." --> [(-1,1), (1,2), (2,-1)]

    Minus signs can be included in the pairs:

    "-11, 12, 2-5" --> [(-1,1), (1,2), (2,-5)]

    """
    arcs = []
    for pair in arcz.split():
        asgn = bsgn = 1
        if len(pair) == 2:
            a, b = pair
        else:
            assert len(pair) == 3
            if pair[0] == '-':
                _, a, b = pair
                asgn = -1
            else:
                assert pair[1] == '-'
                a, _, b = pair
                bsgn = -1
        arcs.append((asgn * _arcz_map[a], bsgn * _arcz_map[b]))
    return sorted(arcs)


_arcz_unmap = {val: ch for ch, val in _arcz_map.items()}

def _arcs_to_arcz_repr_one(num):
    """Return an arcz form of the number `num`, or "?" if there is none."""
    if num == -1:
        return "."
    z = ""
    if num < 0:
        z += "-"
        num *= -1
    z += _arcz_unmap.get(num, "?")
    return z


def arcs_to_arcz_repr(arcs):
    """Convert a list of arcs to a readable multi-line form for asserting.

    Each pair is on its own line, with a comment showing the arcz form,
    to make it easier to decode when debugging test failures.

    """
    repr_list = []
    for a, b in (arcs or ()):
        line = repr((a, b))
        line += " # "
        line += _arcs_to_arcz_repr_one(a)
        line += _arcs_to_arcz_repr_one(b)
        repr_list.append(line)
    return "\n".join(repr_list) + "\n"


@contextlib.contextmanager
def change_dir(new_dir):
    """Change directory, and then change back.

    Use as a context manager, it will return to the original
    directory at the end of the block.

    """
    old_dir = os.getcwd()
    os.chdir(str(new_dir))
    try:
        yield
    finally:
        os.chdir(old_dir)


def without_module(using_module, missing_module_name):
    """
    Hide a module for testing.

    Use this in a test function to make an optional module unavailable during
    the test::

        with without_module(product.something, 'toml'):
            use_toml_somehow()

    Arguments:
        using_module: a module in which to hide `missing_module_name`.
        missing_module_name (str): the name of the module to hide.

    """
    return mock.patch.object(using_module, missing_module_name, None)


def assert_count_equal(a, b):
    """
    A pytest-friendly implementation of assertCountEqual.

    Assert that `a` and `b` have the same elements, but maybe in different order.
    This only works for hashable elements.
    """
    assert collections.Counter(list(a)) == collections.Counter(list(b))