Source code for _pytest.monkeypatch

""" monkeypatching and mocking functionality.  """

import os, sys
from py.builtin import _basestring

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)
        monkeypatch.chdir(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



def derive_importpath(import_path):
    import pytest
    if not isinstance(import_path, _basestring) or "." not in import_path:
        raise TypeError("must be absolute import path string, not %r" %
                        (import_path,))
    rest = []
    target = import_path
    while target:
        try:
            obj = __import__(target, None, None, "__doc__")
        except ImportError:
            if "." not in target:
                __tracebackhide__ = True
                pytest.fail("could not import any sub part: %s" %
                            import_path)
            target, name = target.rsplit(".", 1)
            rest.append(name)
        else:
            assert rest
            try:
                while len(rest) > 1:
                    attr = rest.pop()
                    obj = getattr(obj, attr)
                attr = rest[0]
                getattr(obj, attr)
            except AttributeError:
                __tracebackhide__ = True
                pytest.fail("object %r has no attribute %r" % (obj, attr))
            return attr, obj



notset = object()

[docs]class monkeypatch: """ object keeping a record of setattr/item/env/syspath changes. """ def __init__(self): self._setattr = [] self._setitem = [] self._cwd = None
[docs] 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 x: "/")`` 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, _basestring): 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) 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.insert(0, (target, name, oldval)) setattr(target, name, value)
[docs] 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, the attribute is allowed to not pre-exist. """ __tracebackhide__ = True if name is notset: if not isinstance(target, _basestring): raise TypeError("use delattr(target, name) or " "delattr(target) with target being a dotted " "import string") name, target = derive_importpath(target) if not hasattr(target, name): if raising: raise AttributeError(name) else: self._setattr.insert(0, (target, name, getattr(target, name, notset))) delattr(target, 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 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() else: os.chdir(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: try: del dictionary[name] except KeyError: pass # was already deleted, so we have the desired state else: dictionary[name] = value self._setitem[:] = [] if hasattr(self, '_savesyspath'): sys.path[:] = self._savesyspath del self._savesyspath if self._cwd is not None: os.chdir(self._cwd) self._cwd = None