Declare data dependencies in ThOr functors

By implementing the data_dependencies API added in LHCb!2930 (merged), PyConf can now retrieve data dependencies of functors. The various BoundFunctor specialisations now propagate the dependencies of their inputs to themselves. Complex functors, like MVA and COMB, are responsible for propagating data dependencies from their arguments (which is rather ugly, but I think it's good enough for now).

To support existing tests and allow for gradual migration, strings are allowed in place of DataHandle arguments, but a warning is logged. Users of functors should migrate to using DataHandle.

See Moore#51 (closed) for further motivation.

Requires LHCb!2930 (merged).

Phys/FunctorCore/python/Functors/tests/test_grammar.py

@@ -12,9 +12,11 @@
 from __future__ import print_function
 from __future__ import division
 from past.utils import old_div
+import pickle
 from Functors import PT, ISMUON, MINIPCUT
 from Functors import math as fmath
 from GaudiKernel.SystemOfUnits import *
+from PyConf.Algorithms import Gaudi__Examples__IntDataProducer
 
 
 def not_empty(f):
@@ -79,3 +81,25 @@ def test_disabled_logical_operators():
         pass
     else:
         raise Exception("Use of logical `not` did not raise an exception.")
+
+
+def test_serialisation():
+    """A BoundFunctor must be seriasable by the pickle module."""
+    functor = MINIPCUT(IPCut=1.0, Vertices='Test/Path')
+    # Use the same protocol as in `gaudirun.py -o options.pkl`
+    loaded = pickle.loads(pickle.dumps(functor, protocol=-1))
+    assert functor.code() == loaded.code()
+    assert functor.code_repr() == loaded.code_repr()
+    assert functor.headers() == loaded.headers()
+    assert functor.name() == loaded.name()
+    assert repr(functor) == repr(loaded)
+    assert str(functor) == str(loaded)
+
+    # Should also work with DataHandle inputs
+    pvs = Gaudi__Examples__IntDataProducer().OutputLocation
+    functor = MINIPCUT(IPCut=1.0, Vertices=pvs)
+    loaded = pickle.loads(pickle.dumps(functor, protocol=-1))
+    # It is expected that the data dependencies are lost during serialisation;
+    # see BoundFunctor.__getstate__
+    assert len(functor.data_dependencies()) > len(loaded.data_dependencies())
+    assert len(loaded.data_dependencies()) == 0