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""" monkeypatching and mocking functionality. """ 

from __future__ import absolute_import 

from __future__ import division 

from __future__ import print_function 

 

import os 

import re 

import sys 

import warnings 

from contextlib import contextmanager 

 

import six 

 

import pytest 

from _pytest.fixtures import fixture 

from _pytest.pathlib import Path 

 

RE_IMPORT_ERROR_NAME = re.compile(r"^No module named (.*)$") 

 

 

@fixture 

def monkeypatch(): 

"""The returned ``monkeypatch`` fixture provides these 

helper methods to modify objects, dictionaries or os.environ:: 

 

monkeypatch.setattr(obj, name, value, raising=True) 

monkeypatch.delattr(obj, name, raising=True) 

monkeypatch.setitem(mapping, name, value) 

monkeypatch.delitem(obj, name, raising=True) 

monkeypatch.setenv(name, value, prepend=False) 

monkeypatch.delenv(name, raising=True) 

monkeypatch.syspath_prepend(path) 

monkeypatch.chdir(path) 

 

All modifications will be undone after the requesting 

test function or fixture has finished. The ``raising`` 

parameter determines if a KeyError or AttributeError 

will be raised if the set/deletion operation has no target. 

""" 

mpatch = MonkeyPatch() 

yield mpatch 

mpatch.undo() 

 

 

def resolve(name): 

# simplified from zope.dottedname 

parts = name.split(".") 

 

used = parts.pop(0) 

found = __import__(used) 

for part in parts: 

used += "." + part 

try: 

found = getattr(found, part) 

except AttributeError: 

pass 

else: 

continue 

# we use explicit un-nesting of the handling block in order 

# to avoid nested exceptions on python 3 

try: 

__import__(used) 

except ImportError as ex: 

# str is used for py2 vs py3 

expected = str(ex).split()[-1] 

if expected == used: 

raise 

else: 

raise ImportError("import error in %s: %s" % (used, ex)) 

found = annotated_getattr(found, part, used) 

return found 

 

 

def annotated_getattr(obj, name, ann): 

try: 

obj = getattr(obj, name) 

except AttributeError: 

raise AttributeError( 

"%r object at %s has no attribute %r" % (type(obj).__name__, ann, name) 

) 

return obj 

 

 

def derive_importpath(import_path, raising): 

if not isinstance(import_path, six.string_types) or "." not in import_path: 

raise TypeError("must be absolute import path string, not %r" % (import_path,)) 

module, attr = import_path.rsplit(".", 1) 

target = resolve(module) 

if raising: 

annotated_getattr(target, attr, ann=module) 

return attr, target 

 

 

class Notset(object): 

def __repr__(self): 

return "<notset>" 

 

 

notset = Notset() 

 

 

class MonkeyPatch(object): 

""" Object returned by the ``monkeypatch`` fixture keeping a record of setattr/item/env/syspath changes. 

""" 

 

def __init__(self): 

self._setattr = [] 

self._setitem = [] 

self._cwd = None 

self._savesyspath = None 

 

@contextmanager 

def context(self): 

""" 

Context manager that returns a new :class:`MonkeyPatch` object which 

undoes any patching done inside the ``with`` block upon exit: 

 

.. code-block:: python 

 

import functools 

def test_partial(monkeypatch): 

with monkeypatch.context() as m: 

m.setattr(functools, "partial", 3) 

 

Useful in situations where it is desired to undo some patches before the test ends, 

such as mocking ``stdlib`` functions that might break pytest itself if mocked (for examples 

of this see `#3290 <https://github.com/pytest-dev/pytest/issues/3290>`_. 

""" 

m = MonkeyPatch() 

try: 

yield m 

finally: 

m.undo() 

 

def setattr(self, target, name, value=notset, raising=True): 

""" Set attribute value on target, memorizing the old value. 

By default raise AttributeError if the attribute did not exist. 

 

For convenience you can specify a string as ``target`` which 

will be interpreted as a dotted import path, with the last part 

being the attribute name. Example: 

``monkeypatch.setattr("os.getcwd", lambda: "/")`` 

would set the ``getcwd`` function of the ``os`` module. 

 

The ``raising`` value determines if the setattr should fail 

if the attribute is not already present (defaults to True 

which means it will raise). 

""" 

__tracebackhide__ = True 

import inspect 

 

if value is notset: 

if not isinstance(target, six.string_types): 

raise TypeError( 

"use setattr(target, name, value) or " 

"setattr(target, value) with target being a dotted " 

"import string" 

) 

value = name 

name, target = derive_importpath(target, raising) 

 

oldval = getattr(target, name, notset) 

if raising and oldval is notset: 

raise AttributeError("%r has no attribute %r" % (target, name)) 

 

# avoid class descriptors like staticmethod/classmethod 

if inspect.isclass(target): 

oldval = target.__dict__.get(name, notset) 

self._setattr.append((target, name, oldval)) 

setattr(target, name, value) 

 

def delattr(self, target, name=notset, raising=True): 

""" Delete attribute ``name`` from ``target``, by default raise 

AttributeError it the attribute did not previously exist. 

 

If no ``name`` is specified and ``target`` is a string 

it will be interpreted as a dotted import path with the 

last part being the attribute name. 

 

If ``raising`` is set to False, no exception will be raised if the 

attribute is missing. 

""" 

__tracebackhide__ = True 

import inspect 

 

if name is notset: 

if not isinstance(target, six.string_types): 

raise TypeError( 

"use delattr(target, name) or " 

"delattr(target) with target being a dotted " 

"import string" 

) 

name, target = derive_importpath(target, raising) 

 

if not hasattr(target, name): 

if raising: 

raise AttributeError(name) 

else: 

oldval = getattr(target, name, notset) 

# Avoid class descriptors like staticmethod/classmethod. 

if inspect.isclass(target): 

oldval = target.__dict__.get(name, notset) 

self._setattr.append((target, name, oldval)) 

delattr(target, name) 

 

def setitem(self, dic, name, value): 

""" Set dictionary entry ``name`` to value. """ 

self._setitem.append((dic, name, dic.get(name, notset))) 

dic[name] = value 

 

def delitem(self, dic, name, raising=True): 

""" Delete ``name`` from dict. Raise KeyError if it doesn't exist. 

 

If ``raising`` is set to False, no exception will be raised if the 

key is missing. 

""" 

if name not in dic: 

if raising: 

raise KeyError(name) 

else: 

self._setitem.append((dic, name, dic.get(name, notset))) 

del dic[name] 

 

def _warn_if_env_name_is_not_str(self, name): 

"""On Python 2, warn if the given environment variable name is not a native str (#4056)""" 

if six.PY2 and not isinstance(name, str): 

warnings.warn( 

pytest.PytestWarning( 

"Environment variable name {!r} should be str".format(name) 

) 

) 

 

def setenv(self, name, value, prepend=None): 

""" Set environment variable ``name`` to ``value``. If ``prepend`` 

is a character, read the current environment variable value 

and prepend the ``value`` adjoined with the ``prepend`` character.""" 

if not isinstance(value, str): 

warnings.warn( 

pytest.PytestWarning( 

"Value of environment variable {name} type should be str, but got " 

"{value!r} (type: {type}); converted to str implicitly".format( 

name=name, value=value, type=type(value).__name__ 

) 

), 

stacklevel=2, 

) 

value = str(value) 

if prepend and name in os.environ: 

value = value + prepend + os.environ[name] 

self._warn_if_env_name_is_not_str(name) 

self.setitem(os.environ, name, value) 

 

def delenv(self, name, raising=True): 

""" Delete ``name`` from the environment. Raise KeyError if it does 

not exist. 

 

If ``raising`` is set to False, no exception will be raised if the 

environment variable is missing. 

""" 

self._warn_if_env_name_is_not_str(name) 

self.delitem(os.environ, name, raising=raising) 

 

def syspath_prepend(self, path): 

""" Prepend ``path`` to ``sys.path`` list of import locations. """ 

if self._savesyspath is None: 

self._savesyspath = sys.path[:] 

sys.path.insert(0, str(path)) 

 

def chdir(self, path): 

""" Change the current working directory to the specified path. 

Path can be a string or a py.path.local object. 

""" 

if self._cwd is None: 

self._cwd = os.getcwd() 

if hasattr(path, "chdir"): 

path.chdir() 

elif isinstance(path, Path): 

# modern python uses the fspath protocol here LEGACY 

os.chdir(str(path)) 

else: 

os.chdir(path) 

 

def undo(self): 

""" Undo previous changes. This call consumes the 

undo stack. Calling it a second time has no effect unless 

you do more monkeypatching after the undo call. 

 

There is generally no need to call `undo()`, since it is 

called automatically during tear-down. 

 

Note that the same `monkeypatch` fixture is used across a 

single test function invocation. If `monkeypatch` is used both by 

the test function itself and one of the test fixtures, 

calling `undo()` will undo all of the changes made in 

both functions. 

""" 

for obj, name, value in reversed(self._setattr): 

if value is not notset: 

setattr(obj, name, value) 

else: 

delattr(obj, name) 

self._setattr[:] = [] 

for dictionary, name, value in reversed(self._setitem): 

if value is notset: 

try: 

del dictionary[name] 

except KeyError: 

pass # was already deleted, so we have the desired state 

else: 

dictionary[name] = value 

self._setitem[:] = [] 

if self._savesyspath is not None: 

sys.path[:] = self._savesyspath 

self._savesyspath = None 

 

if self._cwd is not None: 

os.chdir(self._cwd) 

self._cwd = None