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Rewrite cache list decorator
Because it was complicated and annoyed me. I suspect this will be more efficient too.
This commit is contained in:
Richard van der Hoff
parent
b0b5566f36
commit
f102c05856
1
changelog.d/3384.misc
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1
changelog.d/3384.misc
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@ -0,0 +1 @@
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Rewrite cache list decorator
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@ -473,105 +473,101 @@ class CacheListDescriptor(_CacheDescriptorBase):
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@functools.wraps(self.orig)
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def wrapped(*args, **kwargs):
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# If we're passed a cache_context then we'll want to call its invalidate()
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# whenever we are invalidated
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# If we're passed a cache_context then we'll want to call its
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# invalidate() whenever we are invalidated
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invalidate_callback = kwargs.pop("on_invalidate", None)
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arg_dict = inspect.getcallargs(self.orig, obj, *args, **kwargs)
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keyargs = [arg_dict[arg_nm] for arg_nm in self.arg_names]
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list_args = arg_dict[self.list_name]
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# cached is a dict arg -> deferred, where deferred results in a
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# 2-tuple (`arg`, `result`)
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results = {}
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cached_defers = {}
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missing = []
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def update_results_dict(res, arg):
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results[arg] = res
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# list of deferreds to wait for
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cached_defers = []
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missing = set()
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# If the cache takes a single arg then that is used as the key,
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# otherwise a tuple is used.
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if num_args == 1:
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def cache_get(arg):
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return cache.get(arg, callback=invalidate_callback)
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def arg_to_cache_key(arg):
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return arg
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else:
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key = list(keyargs)
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keylist = list(keyargs)
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def cache_get(arg):
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key[self.list_pos] = arg
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return cache.get(tuple(key), callback=invalidate_callback)
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def arg_to_cache_key(arg):
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keylist[self.list_pos] = arg
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return tuple(keylist)
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for arg in list_args:
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try:
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res = cache_get(arg)
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res = cache.get(arg_to_cache_key(arg),
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callback=invalidate_callback)
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if not isinstance(res, ObservableDeferred):
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results[arg] = res
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elif not res.has_succeeded():
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res = res.observe()
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res.addCallback(lambda r, arg: (arg, r), arg)
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cached_defers[arg] = res
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res.addCallback(update_results_dict, arg)
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cached_defers.append(res)
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else:
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results[arg] = res.get_result()
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except KeyError:
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missing.append(arg)
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missing.add(arg)
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if missing:
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args_to_call = dict(arg_dict)
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args_to_call[self.list_name] = missing
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# we need an observable deferred for each entry in the list,
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# which we put in the cache. Each deferred resolves with the
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# relevant result for that key.
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deferreds_map = {}
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for arg in missing:
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deferred = defer.Deferred()
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deferreds_map[arg] = deferred
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key = arg_to_cache_key(arg)
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observable = ObservableDeferred(deferred)
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cache.set(key, observable)
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ret_d = defer.maybeDeferred(
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def complete_all(res):
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# the wrapped function has completed. It returns a
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# a dict. We can now resolve the observable deferreds in
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# the cache and update our own result map.
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for e in missing:
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val = res.get(e, None)
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deferreds_map[e].callback(val)
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results[e] = val
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def errback(f):
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# the wrapped function has failed. Invalidate any cache
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# entries we're supposed to be populating, and fail
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# their deferreds.
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for e in missing:
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key = arg_to_cache_key(e)
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cache.invalidate(key)
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deferreds_map[e].errback(f)
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# return the failure, to propagate to our caller.
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return f
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args_to_call = dict(arg_dict)
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args_to_call[self.list_name] = list(missing)
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cached_defers.append(defer.maybeDeferred(
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logcontext.preserve_fn(self.function_to_call),
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**args_to_call
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)
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ret_d = ObservableDeferred(ret_d)
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# We need to create deferreds for each arg in the list so that
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# we can insert the new deferred into the cache.
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for arg in missing:
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observer = ret_d.observe()
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observer.addCallback(lambda r, arg: r.get(arg, None), arg)
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observer = ObservableDeferred(observer)
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if num_args == 1:
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cache.set(
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arg, observer,
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callback=invalidate_callback
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)
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def invalidate(f, key):
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cache.invalidate(key)
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return f
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observer.addErrback(invalidate, arg)
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else:
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key = list(keyargs)
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key[self.list_pos] = arg
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cache.set(
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tuple(key), observer,
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callback=invalidate_callback
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)
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def invalidate(f, key):
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cache.invalidate(key)
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return f
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observer.addErrback(invalidate, tuple(key))
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res = observer.observe()
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res.addCallback(lambda r, arg: (arg, r), arg)
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cached_defers[arg] = res
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).addCallbacks(complete_all, errback))
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if cached_defers:
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def update_results_dict(res):
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results.update(res)
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return results
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return logcontext.make_deferred_yieldable(defer.gatherResults(
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list(cached_defers.values()),
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d = defer.gatherResults(
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cached_defers,
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consumeErrors=True,
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).addCallback(update_results_dict).addErrback(
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).addCallbacks(
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lambda _: results,
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unwrapFirstError
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))
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)
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return logcontext.make_deferred_yieldable(d)
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else:
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return results
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@ -625,7 +621,8 @@ def cachedList(cached_method_name, list_name, num_args=None, inlineCallbacks=Fal
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cache.
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Args:
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cache (Cache): The underlying cache to use.
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cached_method_name (str): The name of the single-item lookup method.
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This is only used to find the cache to use.
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list_name (str): The name of the argument that is the list to use to
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do batch lookups in the cache.
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num_args (int): Number of arguments to use as the key in the cache
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@ -273,3 +273,64 @@ class DescriptorTestCase(unittest.TestCase):
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r = yield obj.fn(2, 3)
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self.assertEqual(r, 'chips')
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obj.mock.assert_not_called()
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@unittest.DEBUG
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class CachedListDescriptorTestCase(unittest.TestCase):
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@defer.inlineCallbacks
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def test_cache(self):
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class Cls(object):
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def __init__(self):
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self.mock = mock.Mock()
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@descriptors.cached()
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def fn(self, arg1, arg2):
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pass
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@descriptors.cachedList("fn", "args1", inlineCallbacks=True)
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def list_fn(self, args1, arg2):
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assert (
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logcontext.LoggingContext.current_context().request == "c1"
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)
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# we want this to behave like an asynchronous function
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yield run_on_reactor()
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assert (
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logcontext.LoggingContext.current_context().request == "c1"
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)
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defer.returnValue(self.mock(args1, arg2))
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with logcontext.LoggingContext() as c1:
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c1.request = "c1"
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obj = Cls()
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obj.mock.return_value = {10: 'fish', 20: 'chips'}
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d1 = obj.list_fn([10, 20], 2)
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self.assertEqual(
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logcontext.LoggingContext.current_context(),
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logcontext.LoggingContext.sentinel,
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)
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r = yield d1
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self.assertEqual(
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logcontext.LoggingContext.current_context(),
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c1
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)
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obj.mock.assert_called_once_with([10, 20], 2)
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self.assertEqual(r, {10: 'fish', 20: 'chips'})
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obj.mock.reset_mock()
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# a call with different params should call the mock again
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obj.mock.return_value = {30: 'peas'}
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r = yield obj.list_fn([20, 30], 2)
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obj.mock.assert_called_once_with([30], 2)
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self.assertEqual(r, {20: 'chips', 30: 'peas'})
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obj.mock.reset_mock()
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# all the values should now be cached
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r = yield obj.fn(10, 2)
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self.assertEqual(r, 'fish')
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r = yield obj.fn(20, 2)
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self.assertEqual(r, 'chips')
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r = yield obj.fn(30, 2)
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self.assertEqual(r, 'peas')
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r = yield obj.list_fn([10, 20, 30], 2)
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obj.mock.assert_not_called()
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self.assertEqual(r, {10: 'fish', 20: 'chips', 30: 'peas'})
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