FEAT(op): NULL_OP to erase Operations while merging

Author: ankostis

graphtik/__init__.py

@@ -45,4 +45,4 @@
 from .modifiers import mapped, optional, vararg, varargs, sideffect, sideffected, rename_dependency
 from .netop import compose
 from .network import AbortedException, IncompleteExecutionError
-from .op import operation
+from .op import operation, NULL_OP

graphtik/netop.py

@@ -14,7 +14,7 @@
 from .config import is_debug, reset_abort
 from .modifiers import optional, sideffect
 from .network import ExecutionPlan, Network, NodePredicate, Solution, yield_ops
-from .op import FunctionalOperation, Operation, reparse_operation_data
+from .op import FunctionalOperation, NULL_OP, Operation, reparse_operation_data
 
 log = logging.getLogger(__name__)
 
@@ -77,11 +77,10 @@ def proc_op(op, parent=None):
     merge_set = iset()  # Preseve given node order.
     for op in operations:
         if isinstance(op, NetworkOperation):
-            merge_set.update(
-                proc_op(s, op.name) for s in op.net.graph if isinstance(s, Operation)
-            )
+            merge_set.update(proc_op(s, op.name) for s in yield_ops(op.net.graph))
         else:
             merge_set.add(proc_op(op))
+    merge_set = iset(i for i in merge_set if not isinstance(i, NULL_OP))
 
     assert all(bool(n) for n in merge_set)
     net = Network(*merge_set)

graphtik/op.py

@@ -862,3 +862,13 @@ def decorator(*args, **kw):
     decorator.withset = op.withset
 
     return decorator
+
+
+class NULL_OP(FunctionalOperation):
+    """Eliminates same-named operations added later during term:`operation merging`."""
+
+    def __init__(self, name, parents=None):
+        super().__init__(name=name, parents=parents)
+
+    def compute(self, *args, **kw):
+        raise AssertionError("Should have been eliminated!")