143 lines
4.8 KiB
Python
143 lines
4.8 KiB
Python
"""
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safely patch object attributes, dicts and environment variables.
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Usage
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----------------
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Use the `monkeypatch funcarg`_ to tweak your global test environment
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for running a particular test. You can safely set/del an attribute,
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dictionary item or environment variable by respective methods
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on the monkeypatch funcarg. If you want e.g. to set an ENV1 variable
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and have os.path.expanduser return a particular directory, you can
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write it down like this:
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.. sourcecode:: python
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def test_mytest(monkeypatch):
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monkeypatch.setenv('ENV1', 'myval')
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monkeypatch.setattr(os.path, 'expanduser', lambda x: '/tmp/xyz')
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... # your test code that uses those patched values implicitely
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After the test function finished all modifications will be undone,
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because the ``monkeypatch.undo()`` method is registered as a finalizer.
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``monkeypatch.setattr/delattr/delitem/delenv()`` all
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by default raise an Exception if the target does not exist.
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Pass ``raising=False`` if you want to skip this check.
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prepending to PATH or other environment variables
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---------------------------------------------------------
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To prepend a value to an already existing environment parameter:
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.. sourcecode:: python
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def test_mypath_finding(monkeypatch):
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monkeypatch.setenv('PATH', 'x/y', prepend=":")
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# in bash language: export PATH=x/y:$PATH
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calling "undo" finalization explicitely
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-----------------------------------------
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At the end of function execution py.test invokes
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a teardown hook which undoes all monkeypatch changes.
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If you do not want to wait that long you can call
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finalization explicitely::
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monkeypatch.undo()
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This will 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 start monkeypatching after the undo call.
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.. _`monkeypatch blog post`: http://tetamap.wordpress.com/2009/03/03/monkeypatching-in-unit-tests-done-right/
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"""
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import py, os, sys
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def pytest_funcarg__monkeypatch(request):
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"""The returned ``monkeypatch`` funcarg 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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All modifications will be undone when the requesting
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test function finished its execution. For the ``del``
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methods the ``raising`` parameter determines if a
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KeyError or AttributeError will be raised if the
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deletion has no target.
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"""
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monkeypatch = MonkeyPatch()
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request.addfinalizer(monkeypatch.undo)
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return monkeypatch
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notset = object()
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class MonkeyPatch:
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def __init__(self):
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self._setattr = []
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self._setitem = []
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def setattr(self, obj, name, value, raising=True):
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oldval = getattr(obj, name, notset)
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if raising and oldval is notset:
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raise AttributeError("%r has no attribute %r" %(obj, name))
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self._setattr.insert(0, (obj, name, oldval))
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setattr(obj, name, value)
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def delattr(self, obj, name, raising=True):
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if not hasattr(obj, 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.insert(0, (obj, name, getattr(obj, name, notset)))
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delattr(obj, name)
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def setitem(self, dic, name, value):
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self._setitem.insert(0, (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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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.insert(0, (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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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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self.delitem(os.environ, name, raising=raising)
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def syspath_prepend(self, path):
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if not hasattr(self, '_savesyspath'):
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self._savesyspath = sys.path[:]
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sys.path.insert(0, str(path))
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def undo(self):
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for obj, name, value in 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 self._setitem:
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if value is notset:
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del dictionary[name]
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else:
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dictionary[name] = value
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self._setitem[:] = []
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if hasattr(self, '_savesyspath'):
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sys.path[:] = self._savesyspath
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