~testtools-dev/testtools/trunk : contents of testtools/matchers.py at revision 239

~testtools-dev/testtools/trunk : (revision 239)
# Copyright (c) 2009-2011 testtools developers. See LICENSE for details.

"""Matchers, a way to express complex assertions outside the testcase.

Inspired by 'hamcrest'.

Matcher provides the abstract API that all matchers need to implement.

Bundled matchers are listed in __all__: a list can be obtained by running
$ python -c 'import testtools.matchers; print testtools.matchers.__all__'
"""

__metaclass__ = type
__all__ = [
    'AfterPreprocessing',
    'AllMatch',
    'Annotate',
    'Contains',
    'DirExists',
    'DocTestMatches',
    'EndsWith',
    'Equals',
    'FileContains',
    'FileExists',
    'GreaterThan',
    'HasPermissions',
    'Is',
    'IsInstance',
    'KeysEqual',
    'LessThan',
    'MatchesAll',
    'MatchesAny',
    'MatchesException',
    'MatchesListwise',
    'MatchesPredicate',
    'MatchesRegex',
    'MatchesSetwise',
    'MatchesStructure',
    'NotEquals',
    'Not',
    'PathExists',
    'Raises',
    'raises',
    'SamePath',
    'StartsWith',
    'TarballContains',
    ]

import doctest
import operator
from pprint import pformat
import re
import os
import sys
import tarfile
import types

from testtools.compat import (
    classtypes,
    _error_repr,
    isbaseexception,
    _isbytes,
    istext,
    str_is_unicode,
    text_repr
    )


class Matcher(object):
    """A pattern matcher.

    A Matcher must implement match and __str__ to be used by
    testtools.TestCase.assertThat. Matcher.match(thing) returns None when
    thing is completely matched, and a Mismatch object otherwise.

    Matchers can be useful outside of test cases, as they are simply a
    pattern matching language expressed as objects.

    testtools.matchers is inspired by hamcrest, but is pythonic rather than
    a Java transcription.
    """

    def match(self, something):
        """Return None if this matcher matches something, a Mismatch otherwise.
        """
        raise NotImplementedError(self.match)

    def __str__(self):
        """Get a sensible human representation of the matcher.

        This should include the parameters given to the matcher and any
        state that would affect the matches operation.
        """
        raise NotImplementedError(self.__str__)


class Mismatch(object):
    """An object describing a mismatch detected by a Matcher."""

    def __init__(self, description=None, details=None):
        """Construct a `Mismatch`.

        :param description: A description to use.  If not provided,
            `Mismatch.describe` must be implemented.
        :param details: Extra details about the mismatch.  Defaults
            to the empty dict.
        """
        if description:
            self._description = description
        if details is None:
            details = {}
        self._details = details

    def describe(self):
        """Describe the mismatch.

        This should be either a human-readable string or castable to a string.
        In particular, is should either be plain ascii or unicode on Python 2,
        and care should be taken to escape control characters.
        """
        try:
            return self._description
        except AttributeError:
            raise NotImplementedError(self.describe)

    def get_details(self):
        """Get extra details about the mismatch.

        This allows the mismatch to provide extra information beyond the basic
        description, including large text or binary files, or debugging internals
        without having to force it to fit in the output of 'describe'.

        The testtools assertion assertThat will query get_details and attach
        all its values to the test, permitting them to be reported in whatever
        manner the test environment chooses.

        :return: a dict mapping names to Content objects. name is a string to
            name the detail, and the Content object is the detail to add
            to the result. For more information see the API to which items from
            this dict are passed testtools.TestCase.addDetail.
        """
        return getattr(self, '_details', {})

    def __repr__(self):
        return  "<testtools.matchers.Mismatch object at %x attributes=%r>" % (
            id(self), self.__dict__)


class MismatchError(AssertionError):
    """Raised when a mismatch occurs."""

    # This class exists to work around
    # <https://bugs.launchpad.net/testtools/+bug/804127>.  It provides a
    # guaranteed way of getting a readable exception, no matter what crazy
    # characters are in the matchee, matcher or mismatch.

    def __init__(self, matchee, matcher, mismatch, verbose=False):
        # Have to use old-style upcalling for Python 2.4 and 2.5
        # compatibility.
        AssertionError.__init__(self)
        self.matchee = matchee
        self.matcher = matcher
        self.mismatch = mismatch
        self.verbose = verbose

    def __str__(self):
        difference = self.mismatch.describe()
        if self.verbose:
            # GZ 2011-08-24: Smelly API? Better to take any object and special
            #                case text inside?
            if istext(self.matchee) or _isbytes(self.matchee):
                matchee = text_repr(self.matchee, multiline=False)
            else:
                matchee = repr(self.matchee)
            return (
                'Match failed. Matchee: %s\nMatcher: %s\nDifference: %s\n'
                % (matchee, self.matcher, difference))
        else:
            return difference

    if not str_is_unicode:

        __unicode__ = __str__

        def __str__(self):
            return self.__unicode__().encode("ascii", "backslashreplace")


class MismatchDecorator(object):
    """Decorate a ``Mismatch``.

    Forwards all messages to the original mismatch object.  Probably the best
    way to use this is inherit from this class and then provide your own
    custom decoration logic.
    """

    def __init__(self, original):
        """Construct a `MismatchDecorator`.

        :param original: A `Mismatch` object to decorate.
        """
        self.original = original

    def __repr__(self):
        return '<testtools.matchers.MismatchDecorator(%r)>' % (self.original,)

    def describe(self):
        return self.original.describe()

    def get_details(self):
        return self.original.get_details()


class _NonManglingOutputChecker(doctest.OutputChecker):
    """Doctest checker that works with unicode rather than mangling strings

    This is needed because current Python versions have tried to fix string
    encoding related problems, but regressed the default behaviour with
    unicode inputs in the process.

    In Python 2.6 and 2.7 ``OutputChecker.output_difference`` is was changed
    to return a bytestring encoded as per ``sys.stdout.encoding``, or utf-8 if
    that can't be determined. Worse, that encoding process happens in the
    innocent looking `_indent` global function. Because the
    `DocTestMismatch.describe` result may well not be destined for printing to
    stdout, this is no good for us. To get a unicode return as before, the
    method is monkey patched if ``doctest._encoding`` exists.

    Python 3 has a different problem. For some reason both inputs are encoded
    to ascii with 'backslashreplace', making an escaped string matches its
    unescaped form. Overriding the offending ``OutputChecker._toAscii`` method
    is sufficient to revert this.
    """

    def _toAscii(self, s):
        """Return ``s`` unchanged rather than mangling it to ascii"""
        return s

    # Only do this overriding hackery if doctest has a broken _input function
    if getattr(doctest, "_encoding", None) is not None:
        from types import FunctionType as __F
        __f = doctest.OutputChecker.output_difference.im_func
        __g = dict(__f.func_globals)
        def _indent(s, indent=4, _pattern=re.compile("^(?!$)", re.MULTILINE)):
            """Prepend non-empty lines in ``s`` with ``indent`` number of spaces"""
            return _pattern.sub(indent*" ", s)
        __g["_indent"] = _indent
        output_difference = __F(__f.func_code, __g, "output_difference")
        del __F, __f, __g, _indent


class DocTestMatches(object):
    """See if a string matches a doctest example."""

    def __init__(self, example, flags=0):
        """Create a DocTestMatches to match example.

        :param example: The example to match e.g. 'foo bar baz'
        :param flags: doctest comparison flags to match on. e.g.
            doctest.ELLIPSIS.
        """
        if not example.endswith('\n'):
            example += '\n'
        self.want = example # required variable name by doctest.
        self.flags = flags
        self._checker = _NonManglingOutputChecker()

    def __str__(self):
        if self.flags:
            flagstr = ", flags=%d" % self.flags
        else:
            flagstr = ""
        return 'DocTestMatches(%r%s)' % (self.want, flagstr)

    def _with_nl(self, actual):
        result = self.want.__class__(actual)
        if not result.endswith('\n'):
            result += '\n'
        return result

    def match(self, actual):
        with_nl = self._with_nl(actual)
        if self._checker.check_output(self.want, with_nl, self.flags):
            return None
        return DocTestMismatch(self, with_nl)

    def _describe_difference(self, with_nl):
        return self._checker.output_difference(self, with_nl, self.flags)


class DocTestMismatch(Mismatch):
    """Mismatch object for DocTestMatches."""

    def __init__(self, matcher, with_nl):
        self.matcher = matcher
        self.with_nl = with_nl

    def describe(self):
        s = self.matcher._describe_difference(self.with_nl)
        if str_is_unicode or isinstance(s, unicode):
            return s
        # GZ 2011-08-24: This is actually pretty bogus, most C0 codes should
        #                be escaped, in addition to non-ascii bytes.
        return s.decode("latin1").encode("ascii", "backslashreplace")


class DoesNotContain(Mismatch):

    def __init__(self, matchee, needle):
        """Create a DoesNotContain Mismatch.

        :param matchee: the object that did not contain needle.
        :param needle: the needle that 'matchee' was expected to contain.
        """
        self.matchee = matchee
        self.needle = needle

    def describe(self):
        return "%r not in %r" % (self.needle, self.matchee)


class DoesNotStartWith(Mismatch):

    def __init__(self, matchee, expected):
        """Create a DoesNotStartWith Mismatch.

        :param matchee: the string that did not match.
        :param expected: the string that 'matchee' was expected to start with.
        """
        self.matchee = matchee
        self.expected = expected

    def describe(self):
        return "%s does not start with %s." % (
            text_repr(self.matchee), text_repr(self.expected))


class DoesNotEndWith(Mismatch):

    def __init__(self, matchee, expected):
        """Create a DoesNotEndWith Mismatch.

        :param matchee: the string that did not match.
        :param expected: the string that 'matchee' was expected to end with.
        """
        self.matchee = matchee
        self.expected = expected

    def describe(self):
        return "%s does not end with %s." % (
            text_repr(self.matchee), text_repr(self.expected))


class _BinaryComparison(object):
    """Matcher that compares an object to another object."""

    def __init__(self, expected):
        self.expected = expected

    def __str__(self):
        return "%s(%r)" % (self.__class__.__name__, self.expected)

    def match(self, other):
        if self.comparator(other, self.expected):
            return None
        return _BinaryMismatch(self.expected, self.mismatch_string, other)

    def comparator(self, expected, other):
        raise NotImplementedError(self.comparator)


class _BinaryMismatch(Mismatch):
    """Two things did not match."""

    def __init__(self, expected, mismatch_string, other):
        self.expected = expected
        self._mismatch_string = mismatch_string
        self.other = other

    def _format(self, thing):
        # Blocks of text with newlines are formatted as triple-quote
        # strings. Everything else is pretty-printed.
        if istext(thing) or _isbytes(thing):
            return text_repr(thing)
        return pformat(thing)

    def describe(self):
        left = repr(self.expected)
        right = repr(self.other)
        if len(left) + len(right) > 70:
            return "%s:\nreference = %s\nactual    = %s\n" % (
                self._mismatch_string, self._format(self.expected),
                self._format(self.other))
        else:
            return "%s %s %s" % (left, self._mismatch_string, right)


class MatchesPredicate(Matcher):
    """Match if a given function returns True.

    It is reasonably common to want to make a very simple matcher based on a
    function that you already have that returns True or False given a single
    argument (i.e. a predicate function).  This matcher makes it very easy to
    do so. e.g.::

      IsEven = MatchesPredicate(lambda x: x % 2 == 0, '%s is not even')
      self.assertThat(4, IsEven)
    """

    def __init__(self, predicate, message):
        """Create a ``MatchesPredicate`` matcher.

        :param predicate: A function that takes a single argument and returns
            a value that will be interpreted as a boolean.
        :param message: A message to describe a mismatch.  It will be formatted
            with '%' and be given whatever was passed to ``match()``. Thus, it
            needs to contain exactly one thing like '%s', '%d' or '%f'.
        """
        self.predicate = predicate
        self.message = message

    def __str__(self):
        return '%s(%r, %r)' % (
            self.__class__.__name__, self.predicate, self.message)

    def match(self, x):
        if not self.predicate(x):
            return Mismatch(self.message % x)


class Equals(_BinaryComparison):
    """Matches if the items are equal."""

    comparator = operator.eq
    mismatch_string = '!='


class NotEquals(_BinaryComparison):
    """Matches if the items are not equal.

    In most cases, this is equivalent to ``Not(Equals(foo))``. The difference
    only matters when testing ``__ne__`` implementations.
    """

    comparator = operator.ne
    mismatch_string = '=='


class Is(_BinaryComparison):
    """Matches if the items are identical."""

    comparator = operator.is_
    mismatch_string = 'is not'


class IsInstance(object):
    """Matcher that wraps isinstance."""

    def __init__(self, *types):
        self.types = tuple(types)

    def __str__(self):
        return "%s(%s)" % (self.__class__.__name__,
                ', '.join(type.__name__ for type in self.types))

    def match(self, other):
        if isinstance(other, self.types):
            return None
        return NotAnInstance(other, self.types)


class NotAnInstance(Mismatch):

    def __init__(self, matchee, types):
        """Create a NotAnInstance Mismatch.

        :param matchee: the thing which is not an instance of any of types.
        :param types: A tuple of the types which were expected.
        """
        self.matchee = matchee
        self.types = types

    def describe(self):
        if len(self.types) == 1:
            typestr = self.types[0].__name__
        else:
            typestr = 'any of (%s)' % ', '.join(type.__name__ for type in
                    self.types)
        return "'%s' is not an instance of %s" % (self.matchee, typestr)


class LessThan(_BinaryComparison):
    """Matches if the item is less than the matchers reference object."""

    comparator = operator.__lt__
    mismatch_string = 'is not >'


class GreaterThan(_BinaryComparison):
    """Matches if the item is greater than the matchers reference object."""

    comparator = operator.__gt__
    mismatch_string = 'is not <'


class MatchesAny(object):
    """Matches if any of the matchers it is created with match."""

    def __init__(self, *matchers):
        self.matchers = matchers

    def match(self, matchee):
        results = []
        for matcher in self.matchers:
            mismatch = matcher.match(matchee)
            if mismatch is None:
                return None
            results.append(mismatch)
        return MismatchesAll(results)

    def __str__(self):
        return "MatchesAny(%s)" % ', '.join([
            str(matcher) for matcher in self.matchers])


class MatchesAll(object):
    """Matches if all of the matchers it is created with match."""

    def __init__(self, *matchers, **options):
        """Construct a MatchesAll matcher.

        Just list the component matchers as arguments in the ``*args``
        style. If you want only the first mismatch to be reported, past in
        first_only=True as a keyword argument. By default, all mismatches are
        reported.
        """
        self.matchers = matchers
        self.first_only = options.get('first_only', False)

    def __str__(self):
        return 'MatchesAll(%s)' % ', '.join(map(str, self.matchers))

    def match(self, matchee):
        results = []
        for matcher in self.matchers:
            mismatch = matcher.match(matchee)
            if mismatch is not None:
                if self.first_only:
                    return mismatch
                results.append(mismatch)
        if results:
            return MismatchesAll(results)
        else:
            return None


class MismatchesAll(Mismatch):
    """A mismatch with many child mismatches."""

    def __init__(self, mismatches):
        self.mismatches = mismatches

    def describe(self):
        descriptions = ["Differences: ["]
        for mismatch in self.mismatches:
            descriptions.append(mismatch.describe())
        descriptions.append("]")
        return '\n'.join(descriptions)


class Not(object):
    """Inverts a matcher."""

    def __init__(self, matcher):
        self.matcher = matcher

    def __str__(self):
        return 'Not(%s)' % (self.matcher,)

    def match(self, other):
        mismatch = self.matcher.match(other)
        if mismatch is None:
            return MatchedUnexpectedly(self.matcher, other)
        else:
            return None


class MatchedUnexpectedly(Mismatch):
    """A thing matched when it wasn't supposed to."""

    def __init__(self, matcher, other):
        self.matcher = matcher
        self.other = other

    def describe(self):
        return "%r matches %s" % (self.other, self.matcher)


class MatchesException(Matcher):
    """Match an exc_info tuple against an exception instance or type."""

    def __init__(self, exception, value_re=None):
        """Create a MatchesException that will match exc_info's for exception.

        :param exception: Either an exception instance or type.
            If an instance is given, the type and arguments of the exception
            are checked. If a type is given only the type of the exception is
            checked. If a tuple is given, then as with isinstance, any of the
            types in the tuple matching is sufficient to match.
        :param value_re: If 'exception' is a type, and the matchee exception
            is of the right type, then match against this.  If value_re is a
            string, then assume value_re is a regular expression and match
            the str() of the exception against it.  Otherwise, assume value_re
            is a matcher, and match the exception against it.
        """
        Matcher.__init__(self)
        self.expected = exception
        if istext(value_re):
            value_re = AfterPreproccessing(str, MatchesRegex(value_re), False)
        self.value_re = value_re
        self._is_instance = type(self.expected) not in classtypes() + (tuple,)

    def match(self, other):
        if type(other) != tuple:
            return Mismatch('%r is not an exc_info tuple' % other)
        expected_class = self.expected
        if self._is_instance:
            expected_class = expected_class.__class__
        if not issubclass(other[0], expected_class):
            return Mismatch('%r is not a %r' % (other[0], expected_class))
        if self._is_instance:
            if other[1].args != self.expected.args:
                return Mismatch('%s has different arguments to %s.' % (
                        _error_repr(other[1]), _error_repr(self.expected)))
        elif self.value_re is not None:
            return self.value_re.match(other[1])

    def __str__(self):
        if self._is_instance:
            return "MatchesException(%s)" % _error_repr(self.expected)
        return "MatchesException(%s)" % repr(self.expected)


class Contains(Matcher):
    """Checks whether something is container in another thing."""

    def __init__(self, needle):
        """Create a Contains Matcher.

        :param needle: the thing that needs to be contained by matchees.
        """
        self.needle = needle

    def __str__(self):
        return "Contains(%r)" % (self.needle,)

    def match(self, matchee):
        try:
            if self.needle not in matchee:
                return DoesNotContain(matchee, self.needle)
        except TypeError:
            # e.g. 1 in 2 will raise TypeError
            return DoesNotContain(matchee, self.needle)
        return None


class StartsWith(Matcher):
    """Checks whether one string starts with another."""

    def __init__(self, expected):
        """Create a StartsWith Matcher.

        :param expected: the string that matchees should start with.
        """
        self.expected = expected

    def __str__(self):
        return "StartsWith(%r)" % (self.expected,)

    def match(self, matchee):
        if not matchee.startswith(self.expected):
            return DoesNotStartWith(matchee, self.expected)
        return None


class EndsWith(Matcher):
    """Checks whether one string starts with another."""

    def __init__(self, expected):
        """Create a EndsWith Matcher.

        :param expected: the string that matchees should end with.
        """
        self.expected = expected

    def __str__(self):
        return "EndsWith(%r)" % (self.expected,)

    def match(self, matchee):
        if not matchee.endswith(self.expected):
            return DoesNotEndWith(matchee, self.expected)
        return None


class KeysEqual(Matcher):
    """Checks whether a dict has particular keys."""

    def __init__(self, *expected):
        """Create a `KeysEqual` Matcher.

        :param expected: The keys the dict is expected to have.  If a dict,
            then we use the keys of that dict, if a collection, we assume it
            is a collection of expected keys.
        """
        try:
            self.expected = expected.keys()
        except AttributeError:
            self.expected = list(expected)

    def __str__(self):
        return "KeysEqual(%s)" % ', '.join(map(repr, self.expected))

    def match(self, matchee):
        expected = sorted(self.expected)
        matched = Equals(expected).match(sorted(matchee.keys()))
        if matched:
            return AnnotatedMismatch(
                'Keys not equal',
                _BinaryMismatch(expected, 'does not match', matchee))
        return None


class Annotate(object):
    """Annotates a matcher with a descriptive string.

    Mismatches are then described as '<mismatch>: <annotation>'.
    """

    def __init__(self, annotation, matcher):
        self.annotation = annotation
        self.matcher = matcher

    @classmethod
    def if_message(cls, annotation, matcher):
        """Annotate ``matcher`` only if ``annotation`` is non-empty."""
        if not annotation:
            return matcher
        return cls(annotation, matcher)

    def __str__(self):
        return 'Annotate(%r, %s)' % (self.annotation, self.matcher)

    def match(self, other):
        mismatch = self.matcher.match(other)
        if mismatch is not None:
            return AnnotatedMismatch(self.annotation, mismatch)


class AnnotatedMismatch(MismatchDecorator):
    """A mismatch annotated with a descriptive string."""

    def __init__(self, annotation, mismatch):
        super(AnnotatedMismatch, self).__init__(mismatch)
        self.annotation = annotation
        self.mismatch = mismatch

    def describe(self):
        return '%s: %s' % (self.original.describe(), self.annotation)


class Raises(Matcher):
    """Match if the matchee raises an exception when called.

    Exceptions which are not subclasses of Exception propogate out of the
    Raises.match call unless they are explicitly matched.
    """

    def __init__(self, exception_matcher=None):
        """Create a Raises matcher.

        :param exception_matcher: Optional validator for the exception raised
            by matchee. If supplied the exc_info tuple for the exception raised
            is passed into that matcher. If no exception_matcher is supplied
            then the simple fact of raising an exception is considered enough
            to match on.
        """
        self.exception_matcher = exception_matcher

    def match(self, matchee):
        try:
            result = matchee()
            return Mismatch('%r returned %r' % (matchee, result))
        # Catch all exceptions: Raises() should be able to match a
        # KeyboardInterrupt or SystemExit.
        except:
            exc_info = sys.exc_info()
            if self.exception_matcher:
                mismatch = self.exception_matcher.match(exc_info)
                if not mismatch:
                    del exc_info
                    return
            else:
                mismatch = None
            # The exception did not match, or no explicit matching logic was
            # performed. If the exception is a non-user exception (that is, not
            # a subclass of Exception on Python 2.5+) then propogate it.
            if isbaseexception(exc_info[1]):
                del exc_info
                raise
            return mismatch

    def __str__(self):
        return 'Raises()'


def raises(exception):
    """Make a matcher that checks that a callable raises an exception.

    This is a convenience function, exactly equivalent to::

        return Raises(MatchesException(exception))

    See `Raises` and `MatchesException` for more information.
    """
    return Raises(MatchesException(exception))


class MatchesListwise(object):
    """Matches if each matcher matches the corresponding value.

    More easily explained by example than in words:

    >>> MatchesListwise([Equals(1)]).match([1])
    >>> MatchesListwise([Equals(1), Equals(2)]).match([1, 2])
    >>> print (MatchesListwise([Equals(1), Equals(2)]).match([2, 1]).describe())
    Differences: [
    1 != 2
    2 != 1
    ]
    >>> matcher = MatchesListwise([Equals(1), Equals(2)], first_only=True)
    >>> print (matcher.match([3, 4]).describe())
    1 != 3
    """

    def __init__(self, matchers, first_only=False):
        """Construct a MatchesListwise matcher.

        :param matchers: A list of matcher that the matched values must match.
        :param first_only: If True, then only report the first mismatch,
            otherwise report all of them. Defaults to False.
        """
        self.matchers = matchers
        self.first_only = first_only

    def match(self, values):
        mismatches = []
        length_mismatch = Annotate(
            "Length mismatch", Equals(len(self.matchers))).match(len(values))
        if length_mismatch:
            mismatches.append(length_mismatch)
        for matcher, value in zip(self.matchers, values):
            mismatch = matcher.match(value)
            if mismatch:
                if self.first_only:
                    return mismatch
                mismatches.append(mismatch)
        if mismatches:
            return MismatchesAll(mismatches)


class MatchesStructure(object):
    """Matcher that matches an object structurally.

    'Structurally' here means that attributes of the object being matched are
    compared against given matchers.

    `fromExample` allows the creation of a matcher from a prototype object and
    then modified versions can be created with `update`.

    `byEquality` creates a matcher in much the same way as the constructor,
    except that the matcher for each of the attributes is assumed to be
    `Equals`.

    `byMatcher` creates a similar matcher to `byEquality`, but you get to pick
    the matcher, rather than just using `Equals`.
    """

    def __init__(self, **kwargs):
        """Construct a `MatchesStructure`.

        :param kwargs: A mapping of attributes to matchers.
        """
        self.kws = kwargs

    @classmethod
    def byEquality(cls, **kwargs):
        """Matches an object where the attributes equal the keyword values.

        Similar to the constructor, except that the matcher is assumed to be
        Equals.
        """
        return cls.byMatcher(Equals, **kwargs)

    @classmethod
    def byMatcher(cls, matcher, **kwargs):
        """Matches an object where the attributes match the keyword values.

        Similar to the constructor, except that the provided matcher is used
        to match all of the values.
        """
        return cls(
            **dict((name, matcher(value)) for name, value in kwargs.items()))

    @classmethod
    def fromExample(cls, example, *attributes):
        kwargs = {}
        for attr in attributes:
            kwargs[attr] = Equals(getattr(example, attr))
        return cls(**kwargs)

    def update(self, **kws):
        new_kws = self.kws.copy()
        for attr, matcher in kws.items():
            if matcher is None:
                new_kws.pop(attr, None)
            else:
                new_kws[attr] = matcher
        return type(self)(**new_kws)

    def __str__(self):
        kws = []
        for attr, matcher in sorted(self.kws.items()):
            kws.append("%s=%s" % (attr, matcher))
        return "%s(%s)" % (self.__class__.__name__, ', '.join(kws))

    def match(self, value):
        matchers = []
        values = []
        for attr, matcher in sorted(self.kws.items()):
            matchers.append(Annotate(attr, matcher))
            values.append(getattr(value, attr))
        return MatchesListwise(matchers).match(values)


class MatchesRegex(object):
    """Matches if the matchee is matched by a regular expression."""

    def __init__(self, pattern, flags=0):
        self.pattern = pattern
        self.flags = flags

    def __str__(self):
        args = ['%r' % self.pattern]
        flag_arg = []
        # dir() sorts the attributes for us, so we don't need to do it again.
        for flag in dir(re):
            if len(flag) == 1:
                if self.flags & getattr(re, flag):
                    flag_arg.append('re.%s' % flag)
        if flag_arg:
            args.append('|'.join(flag_arg))
        return '%s(%s)' % (self.__class__.__name__, ', '.join(args))

    def match(self, value):
        if not re.match(self.pattern, value, self.flags):
            pattern = self.pattern
            if not isinstance(pattern, str_is_unicode and str or unicode):
                pattern = pattern.decode("latin1")
            pattern = pattern.encode("unicode_escape").decode("ascii")
            return Mismatch("%r does not match /%s/" % (
                    value, pattern.replace("\\\\", "\\")))


class MatchesSetwise(object):
    """Matches if all the matchers match elements of the value being matched.

    That is, each element in the 'observed' set must match exactly one matcher
    from the set of matchers, with no matchers left over.

    The difference compared to `MatchesListwise` is that the order of the
    matchings does not matter.
    """

    def __init__(self, *matchers):
        self.matchers = matchers

    def match(self, observed):
        remaining_matchers = set(self.matchers)
        not_matched = []
        for value in observed:
            for matcher in remaining_matchers:
                if matcher.match(value) is None:
                    remaining_matchers.remove(matcher)
                    break
            else:
                not_matched.append(value)
        if not_matched or remaining_matchers:
            remaining_matchers = list(remaining_matchers)
            # There are various cases that all should be reported somewhat
            # differently.

            # There are two trivial cases:
            # 1) There are just some matchers left over.
            # 2) There are just some values left over.

            # Then there are three more interesting cases:
            # 3) There are the same number of matchers and values left over.
            # 4) There are more matchers left over than values.
            # 5) There are more values left over than matchers.

            if len(not_matched) == 0:
                if len(remaining_matchers) > 1:
                    msg = "There were %s matchers left over: " % (
                        len(remaining_matchers),)
                else:
                    msg = "There was 1 matcher left over: "
                msg += ', '.join(map(str, remaining_matchers))
                return Mismatch(msg)
            elif len(remaining_matchers) == 0:
                if len(not_matched) > 1:
                    return Mismatch(
                        "There were %s values left over: %s" % (
                            len(not_matched), not_matched))
                else:
                    return Mismatch(
                        "There was 1 value left over: %s" % (
                            not_matched, ))
            else:
                common_length = min(len(remaining_matchers), len(not_matched))
                if common_length == 0:
                    raise AssertionError("common_length can't be 0 here")
                if common_length > 1:
                    msg = "There were %s mismatches" % (common_length,)
                else:
                    msg = "There was 1 mismatch"
                if len(remaining_matchers) > len(not_matched):
                    extra_matchers = remaining_matchers[common_length:]
                    msg += " and %s extra matcher" % (len(extra_matchers), )
                    if len(extra_matchers) > 1:
                        msg += "s"
                    msg += ': ' + ', '.join(map(str, extra_matchers))
                elif len(not_matched) > len(remaining_matchers):
                    extra_values = not_matched[common_length:]
                    msg += " and %s extra value" % (len(extra_values), )
                    if len(extra_values) > 1:
                        msg += "s"
                    msg += ': ' + str(extra_values)
                return Annotate(
                    msg, MatchesListwise(remaining_matchers[:common_length])
                    ).match(not_matched[:common_length])


class AfterPreprocessing(object):
    """Matches if the value matches after passing through a function.

    This can be used to aid in creating trivial matchers as functions, for
    example::

      def PathHasFileContent(content):
          def _read(path):
              return open(path).read()
          return AfterPreprocessing(_read, Equals(content))
    """

    def __init__(self, preprocessor, matcher, annotate=True):
        """Create an AfterPreprocessing matcher.

        :param preprocessor: A function called with the matchee before
            matching.
        :param matcher: What to match the preprocessed matchee against.
        :param annotate: Whether or not to annotate the matcher with
            something explaining how we transformed the matchee. Defaults
            to True.
        """
        self.preprocessor = preprocessor
        self.matcher = matcher
        self.annotate = annotate

    def _str_preprocessor(self):
        if isinstance(self.preprocessor, types.FunctionType):
            return '<function %s>' % self.preprocessor.__name__
        return str(self.preprocessor)

    def __str__(self):
        return "AfterPreprocessing(%s, %s)" % (
            self._str_preprocessor(), self.matcher)

    def match(self, value):
        after = self.preprocessor(value)
        if self.annotate:
            matcher = Annotate(
                "after %s on %r" % (self._str_preprocessor(), value),
                self.matcher)
        else:
            matcher = self.matcher
        return matcher.match(after)

# This is the old, deprecated. spelling of the name, kept for backwards
# compatibility.
AfterPreproccessing = AfterPreprocessing


class AllMatch(object):
    """Matches if all provided values match the given matcher."""

    def __init__(self, matcher):
        self.matcher = matcher

    def __str__(self):
        return 'AllMatch(%s)' % (self.matcher,)

    def match(self, values):
        mismatches = []
        for value in values:
            mismatch = self.matcher.match(value)
            if mismatch:
                mismatches.append(mismatch)
        if mismatches:
            return MismatchesAll(mismatches)


def PathExists():
    """Matches if the given path exists.

    Use like this::

      assertThat('/some/path', PathExists())
    """
    return MatchesPredicate(os.path.exists, "%s does not exist.")


def DirExists():
    """Matches if the path exists and is a directory."""
    return MatchesAll(
        PathExists(),
        MatchesPredicate(os.path.isdir, "%s is not a directory."),
        first_only=True)


def FileExists():
    """Matches if the given path exists and is a file."""
    return MatchesAll(
        PathExists(),
        MatchesPredicate(os.path.isfile, "%s is not a file."),
        first_only=True)


class DirContains(Matcher):
    """Matches if the given directory contains files with the given names.

    That is, is the directory listing exactly equal to the given files?
    """

    def __init__(self, filenames=None, matcher=None):
        """Construct a ``DirContains`` matcher.

        Can be used in a basic mode where the whole directory listing is
        matched against an expected directory listing (by passing
        ``filenames``).  Can also be used in a more advanced way where the
        whole directory listing is matched against an arbitrary matcher (by
        passing ``matcher`` instead).

        :param filenames: If specified, match the sorted directory listing
            against this list of filenames, sorted.
        :param matcher: If specified, match the sorted directory listing
            against this matcher.
        """
        if filenames == matcher == None:
            raise AssertionError(
                "Must provide one of `filenames` or `matcher`.")
        if None not in (filenames, matcher):
            raise AssertionError(
                "Must provide either `filenames` or `matcher`, not both.")
        if filenames is None:
            self.matcher = matcher
        else:
            self.matcher = Equals(sorted(filenames))

    def match(self, path):
        mismatch = DirExists().match(path)
        if mismatch is not None:
            return mismatch
        return self.matcher.match(sorted(os.listdir(path)))


class FileContains(Matcher):
    """Matches if the given file has the specified contents."""

    def __init__(self, contents=None, matcher=None):
        """Construct a ``FileContains`` matcher.

        Can be used in a basic mode where the file contents are compared for
        equality against the expected file contents (by passing ``contents``).
        Can also be used in a more advanced way where the file contents are
        matched against an arbitrary matcher (by passing ``matcher`` instead).

        :param contents: If specified, match the contents of the file with
            these contents.
        :param matcher: If specified, match the contents of the file against
            this matcher.
        """
        if contents == matcher == None:
            raise AssertionError(
                "Must provide one of `contents` or `matcher`.")
        if None not in (contents, matcher):
            raise AssertionError(
                "Must provide either `contents` or `matcher`, not both.")
        if matcher is None:
            self.matcher = Equals(contents)
        else:
            self.matcher = matcher

    def match(self, path):
        mismatch = PathExists().match(path)
        if mismatch is not None:
            return mismatch
        f = open(path)
        try:
            actual_contents = f.read()
            return self.matcher.match(actual_contents)
        finally:
            f.close()

    def __str__(self):
        return "File at path exists and contains %s" % self.contents


class TarballContains(Matcher):
    """Matches if the given tarball contains the given paths.

    Uses TarFile.getnames() to get the paths out of the tarball.
    """

    def __init__(self, paths):
        super(TarballContains, self).__init__()
        self.paths = paths
        self.path_matcher = Equals(sorted(self.paths))

    def match(self, tarball_path):
        # Open underlying file first to ensure it's always closed:
        # <http://bugs.python.org/issue10233>
        f = open(tarball_path, "rb")
        try:
            tarball = tarfile.open(tarball_path, fileobj=f)
            try:
                return self.path_matcher.match(sorted(tarball.getnames()))
            finally:
                tarball.close()
        finally:
            f.close()


class SamePath(Matcher):
    """Matches if two paths are the same.

    That is, the paths are equal, or they point to the same file but in
    different ways.  The paths do not have to exist.
    """

    def __init__(self, path):
        super(SamePath, self).__init__()
        self.path = path

    def match(self, other_path):
        f = lambda x: os.path.abspath(os.path.realpath(x))
        return Equals(f(self.path)).match(f(other_path))


class HasPermissions(Matcher):
    """Matches if a file has the given permissions.

    Permissions are specified and matched as a four-digit octal string.
    """

    def __init__(self, octal_permissions):
        """Construct a HasPermissions matcher.

        :param octal_permissions: A four digit octal string, representing the
            intended access permissions. e.g. '0775' for rwxrwxr-x.
        """
        super(HasPermissions, self).__init__()
        self.octal_permissions = octal_permissions

    def match(self, filename):
        permissions = oct(os.stat(filename).st_mode)[-4:]
        return Equals(self.octal_permissions).match(permissions)


# Signal that this is part of the testing framework, and that code from this
# should not normally appear in tracebacks.
__unittest = True