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Source code for _pytest.monkeypatch

""" monkeypatching and mocking functionality.  """

import os, sys

def pytest_funcarg__monkeypatch(request):
    """The returned ``monkeypatch`` funcarg 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, value, raising=True)
        monkeypatch.syspath_prepend(path)

    All modifications will be undone after the requesting
    test function has finished. The ``raising``
    parameter determines if a KeyError or AttributeError
    will be raised if the set/deletion operation has no target.
    """
    mpatch = monkeypatch()
    request.addfinalizer(mpatch.undo)
    return mpatch

notset = object()

[docs]class monkeypatch: """ object keeping a record of setattr/item/env/syspath changes. """ def __init__(self): self._setattr = [] self._setitem = []
[docs] def setattr(self, obj, name, value, raising=True): """ set attribute ``name`` on ``obj`` to ``value``, by default raise AttributeEror if the attribute did not exist. """ oldval = getattr(obj, name, notset) if raising and oldval is notset: raise AttributeError("%r has no attribute %r" %(obj, name)) self._setattr.insert(0, (obj, name, oldval)) setattr(obj, name, value)
[docs] def delattr(self, obj, name, raising=True): """ delete attribute ``name`` from ``obj``, by default raise AttributeError it the attribute did not previously exist. """ if not hasattr(obj, name): if raising: raise AttributeError(name) else: self._setattr.insert(0, (obj, name, getattr(obj, name, notset))) delattr(obj, name)
[docs] def setitem(self, dic, name, value): """ set dictionary entry ``name`` to value. """ self._setitem.insert(0, (dic, name, dic.get(name, notset))) dic[name] = value
[docs] def delitem(self, dic, name, raising=True): """ delete ``name`` from dict, raise KeyError if it doesn't exist.""" if name not in dic: if raising: raise KeyError(name) else: self._setitem.insert(0, (dic, name, dic.get(name, notset))) del dic[name]
[docs] 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.""" value = str(value) if prepend and name in os.environ: value = value + prepend + os.environ[name] self.setitem(os.environ, name, value)
[docs] def delenv(self, name, raising=True): """ delete ``name`` from environment, raise KeyError it not exists.""" self.delitem(os.environ, name, raising=raising)
[docs] def syspath_prepend(self, path): """ prepend ``path`` to ``sys.path`` list of import locations. """ if not hasattr(self, '_savesyspath'): self._savesyspath = sys.path[:] sys.path.insert(0, str(path))
[docs] 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.""" for obj, name, value in self._setattr: if value is not notset: setattr(obj, name, value) else: delattr(obj, name) self._setattr[:] = [] for dictionary, name, value in self._setitem: if value is notset: del dictionary[name] else: dictionary[name] = value self._setitem[:] = [] if hasattr(self, '_savesyspath'): sys.path[:] = self._savesyspath