284 lines
9.6 KiB
Python
284 lines
9.6 KiB
Python
""" monkeypatching and mocking functionality. """
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from __future__ import absolute_import, division, print_function
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import os
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import sys
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import re
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from contextlib import contextmanager
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import six
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from _pytest.fixtures import fixture
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RE_IMPORT_ERROR_NAME = re.compile("^No module named (.*)$")
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@fixture
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def monkeypatch():
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"""The returned ``monkeypatch`` fixture provides these
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helper methods to modify objects, dictionaries or os.environ::
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monkeypatch.setattr(obj, name, value, raising=True)
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monkeypatch.delattr(obj, name, raising=True)
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monkeypatch.setitem(mapping, name, value)
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monkeypatch.delitem(obj, name, raising=True)
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monkeypatch.setenv(name, value, prepend=False)
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monkeypatch.delenv(name, value, raising=True)
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monkeypatch.syspath_prepend(path)
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monkeypatch.chdir(path)
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All modifications will be undone after the requesting
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test function or fixture has finished. The ``raising``
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parameter determines if a KeyError or AttributeError
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will be raised if the set/deletion operation has no target.
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"""
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mpatch = MonkeyPatch()
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yield mpatch
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mpatch.undo()
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def resolve(name):
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# simplified from zope.dottedname
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parts = name.split('.')
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used = parts.pop(0)
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found = __import__(used)
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for part in parts:
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used += '.' + part
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try:
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found = getattr(found, part)
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except AttributeError:
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pass
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else:
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continue
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# we use explicit un-nesting of the handling block in order
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# to avoid nested exceptions on python 3
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try:
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__import__(used)
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except ImportError as ex:
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# str is used for py2 vs py3
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expected = str(ex).split()[-1]
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if expected == used:
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raise
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else:
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raise ImportError(
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'import error in %s: %s' % (used, ex)
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)
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found = annotated_getattr(found, part, used)
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return found
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def annotated_getattr(obj, name, ann):
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try:
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obj = getattr(obj, name)
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except AttributeError:
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raise AttributeError(
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'%r object at %s has no attribute %r' % (
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type(obj).__name__, ann, name
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)
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)
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return obj
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def derive_importpath(import_path, raising):
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if not isinstance(import_path, six.string_types) or "." not in import_path:
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raise TypeError("must be absolute import path string, not %r" %
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(import_path,))
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module, attr = import_path.rsplit('.', 1)
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target = resolve(module)
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if raising:
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annotated_getattr(target, attr, ann=module)
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return attr, target
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class Notset(object):
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def __repr__(self):
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return "<notset>"
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notset = Notset()
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class MonkeyPatch(object):
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""" Object returned by the ``monkeypatch`` fixture keeping a record of setattr/item/env/syspath changes.
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"""
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def __init__(self):
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self._setattr = []
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self._setitem = []
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self._cwd = None
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self._savesyspath = None
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@contextmanager
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def context(self):
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"""
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Context manager that returns a new :class:`MonkeyPatch` object which
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undoes any patching done inside the ``with`` block upon exit:
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.. code-block:: python
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import functools
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def test_partial(monkeypatch):
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with monkeypatch.context() as m:
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m.setattr(functools, "partial", 3)
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Useful in situations where it is desired to undo some patches before the test ends,
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such as mocking ``stdlib`` functions that might break pytest itself if mocked (for examples
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of this see `#3290 <https://github.com/pytest-dev/pytest/issues/3290>`_.
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"""
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m = MonkeyPatch()
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try:
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yield m
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finally:
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m.undo()
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def setattr(self, target, name, value=notset, raising=True):
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""" Set attribute value on target, memorizing the old value.
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By default raise AttributeError if the attribute did not exist.
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For convenience you can specify a string as ``target`` which
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will be interpreted as a dotted import path, with the last part
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being the attribute name. Example:
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``monkeypatch.setattr("os.getcwd", lambda: "/")``
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would set the ``getcwd`` function of the ``os`` module.
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The ``raising`` value determines if the setattr should fail
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if the attribute is not already present (defaults to True
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which means it will raise).
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"""
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__tracebackhide__ = True
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import inspect
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if value is notset:
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if not isinstance(target, six.string_types):
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raise TypeError("use setattr(target, name, value) or "
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"setattr(target, value) with target being a dotted "
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"import string")
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value = name
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name, target = derive_importpath(target, raising)
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oldval = getattr(target, name, notset)
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if raising and oldval is notset:
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raise AttributeError("%r has no attribute %r" % (target, name))
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# avoid class descriptors like staticmethod/classmethod
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if inspect.isclass(target):
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oldval = target.__dict__.get(name, notset)
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self._setattr.append((target, name, oldval))
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setattr(target, name, value)
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def delattr(self, target, name=notset, raising=True):
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""" Delete attribute ``name`` from ``target``, by default raise
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AttributeError it the attribute did not previously exist.
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If no ``name`` is specified and ``target`` is a string
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it will be interpreted as a dotted import path with the
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last part being the attribute name.
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If ``raising`` is set to False, no exception will be raised if the
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attribute is missing.
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"""
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__tracebackhide__ = True
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if name is notset:
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if not isinstance(target, six.string_types):
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raise TypeError("use delattr(target, name) or "
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"delattr(target) with target being a dotted "
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"import string")
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name, target = derive_importpath(target, raising)
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if not hasattr(target, name):
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if raising:
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raise AttributeError(name)
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else:
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self._setattr.append((target, name, getattr(target, name, notset)))
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delattr(target, name)
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def setitem(self, dic, name, value):
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""" Set dictionary entry ``name`` to value. """
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self._setitem.append((dic, name, dic.get(name, notset)))
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dic[name] = value
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def delitem(self, dic, name, raising=True):
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""" Delete ``name`` from dict. Raise KeyError if it doesn't exist.
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If ``raising`` is set to False, no exception will be raised if the
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key is missing.
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"""
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if name not in dic:
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if raising:
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raise KeyError(name)
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else:
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self._setitem.append((dic, name, dic.get(name, notset)))
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del dic[name]
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def setenv(self, name, value, prepend=None):
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""" Set environment variable ``name`` to ``value``. If ``prepend``
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is a character, read the current environment variable value
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and prepend the ``value`` adjoined with the ``prepend`` character."""
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value = str(value)
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if prepend and name in os.environ:
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value = value + prepend + os.environ[name]
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self.setitem(os.environ, name, value)
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def delenv(self, name, raising=True):
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""" Delete ``name`` from the environment. Raise KeyError it does not
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exist.
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If ``raising`` is set to False, no exception will be raised if the
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environment variable is missing.
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"""
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self.delitem(os.environ, name, raising=raising)
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def syspath_prepend(self, path):
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""" Prepend ``path`` to ``sys.path`` list of import locations. """
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if self._savesyspath is None:
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self._savesyspath = sys.path[:]
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sys.path.insert(0, str(path))
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def chdir(self, path):
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""" Change the current working directory to the specified path.
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Path can be a string or a py.path.local object.
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"""
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if self._cwd is None:
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self._cwd = os.getcwd()
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if hasattr(path, "chdir"):
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path.chdir()
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else:
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os.chdir(path)
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def undo(self):
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""" Undo previous changes. This call consumes the
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undo stack. Calling it a second time has no effect unless
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you do more monkeypatching after the undo call.
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There is generally no need to call `undo()`, since it is
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called automatically during tear-down.
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Note that the same `monkeypatch` fixture is used across a
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single test function invocation. If `monkeypatch` is used both by
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the test function itself and one of the test fixtures,
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calling `undo()` will undo all of the changes made in
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both functions.
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"""
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for obj, name, value in reversed(self._setattr):
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if value is not notset:
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setattr(obj, name, value)
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else:
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delattr(obj, name)
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self._setattr[:] = []
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for dictionary, name, value in reversed(self._setitem):
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if value is notset:
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try:
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del dictionary[name]
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except KeyError:
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pass # was already deleted, so we have the desired state
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else:
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dictionary[name] = value
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self._setitem[:] = []
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if self._savesyspath is not None:
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sys.path[:] = self._savesyspath
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self._savesyspath = None
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if self._cwd is not None:
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os.chdir(self._cwd)
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self._cwd = None
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