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POAccess an injected object's containing object?
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copied!<p>Given an object A, which contains a callable object B, is there a way to determine "A" from inside <code>B.__call__()</code>?</p> <p>This is for use in test injection, where A.B is originally a method.</p> <p>The code is something like this:</p> <pre><code># Class to be tested. class Outer(object): def __init__(self, arg): self.arg = arg def func(self, *args, **kwargs): print ('Outer self: %r' % (self,)) # Framework-provided: class Injected(object): def __init__(self): self._replay = False self._calls = [] def replay(self): self._replay = True self._calls.reverse() def __call__(self, *args, **kwargs): if not self._replay: expected = (args[0], args[1:], kwargs) self._calls.append(expected) else: expected_s, expected_a, expected_k = self._calls.pop() ok = True # verify args, similar for expected_k == kwargs ok = reduce(lambda x, comp: x and comp[0](comp[1]), zip(expected_a, args), ok) # what to do for expected_s == self? # ok = ok and expected_s(this) ### <= need "this". ### if not ok: raise Exception('Expectations not matched.') # Inject: setattr(Outer, 'func', Injected()) # Set expectations: # - One object, initialised with "3", must pass "here" as 2nd arg. # - One object, initialised with "4", must pass "whatever" as 1st arg. Outer.func(lambda x: x.arg == 3, lambda x: True, lambda x: x=='here') Outer.func(lambda x: x.arg == 4, lambda x: x=='whatever', lambda x: True) Outer.func.replay() # Invoke other code, which ends up doing: o = Outer(3) p = Outer(5) o.func('something', 'here') p.func('whatever', 'next') # <- This should fail, 5 != 4 </code></pre> <p>The question is: Is there a way (black magic is fine) within <code>Injected.__call__()</code> to access what "self" <em>would have been</em> in non-overwritten <code>Outer.func()</code>, to use as "this" (line marked with "###")?</p> <p>Naturally, the code is a bit more complex (the calls can be configured to be in arbitrary order, return values can be set, etc.), but this is the minimal example I could come up with that demonstrates both the problem and most of the constraints.</p> <p>I cannot inject a function with a default argument instead of <code>Outer.func</code> - that breaks recording (if a function were injected, it'd be an unbound method and require an instance of "Outer" as its first argument, rather than a comparator/validator). </p> <p>Theoretically, I could mock out "Outer" completely for its caller. However, setting up the expectations there would probably be more code, and not reusable elsewhere - any similar case/project would also have to reimplement "Outer" (or its equivalent) as a mock.</p>

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