def _help_tasklet_along(self, gen, val=None, exc=None, tb=None):
# XXX Docstring
info = utils.gen_info(gen)
__ndb_debug__ = info
try:
save_context = get_context()
try:
set_context(self._context)
if exc is not None:
logging.debug('Throwing %s(%s) into %s',
exc.__class__.__name__, exc, info)
value = gen.throw(exc.__class__, exc, tb)
else:
logging.debug('Sending %r to %s', val, info)
value = gen.send(val)
self._context = get_context()
finally:
set_context(save_context)
except StopIteration, err:
result = get_return_value(err)
logging.debug('%s returned %r', info, result)
self.set_result(result)
return
if isinstance(value, datastore_rpc.MultiRpc):
# TODO: Tail recursion if the RPC is already complete.
if len(value.rpcs) == 1:
value = value.rpcs[0]
# Fall through to next isinstance test.
else:
assert False # TODO: Support MultiRpc using MultiFuture.
if isinstance(value, UserRPC):
# TODO: Tail recursion if the RPC is already complete.
eventloop.queue_rpc(value, self._on_rpc_completion, value, gen)
return
if isinstance(value, Future):
# TODO: Tail recursion if the Future is already done.
assert not self._next, self._next
self._next = value
self._geninfo = utils.gen_info(gen)
logging.debug('%s is now blocked waiting for %s', self, value)
value.add_callback(self._on_future_completion, value, gen)
return
if isinstance(value, (tuple, list)):
# Arrange for yield to return a list of results (not Futures).
info = 'multi-yield from ' + utils.gen_info(gen)
mfut = MultiFuture(info)
for subfuture in value:
mfut.add_dependent(subfuture)
mfut.complete()
mfut.add_callback(self._on_future_completion, mfut, gen)
return
if is_generator(value):
assert False # TODO: emulate PEP 380 here?
assert False # A tasklet shouldn't yield plain values.