make state usable if reducer or its upstream is unactionable

Author: molaxx

computation_graph/composers/memory.py

@@ -53,4 +53,13 @@ def lag(state, current):
 
 @gamla.curry
 def with_state(key: str, default, f: Callable) -> base_types.GraphType:
-    return composers.make_compose_future(f, f, key, default)
+    # Include a bypass for last state if reducer (or its upstream) in current state is unactionable
+    def passthrough(x):
+        return x
+
+    f_with_bypass = composers.make_first(f, passthrough)
+
+    return base_types.merge_graphs(
+        composers.make_compose_future(f, f_with_bypass, key, default),
+        composers.make_compose_future(passthrough, f_with_bypass, None, default),
+    )

computation_graph/graph_runners.py

@@ -80,10 +80,11 @@ def variadic_with_state_and_expectations(g, sink):
     def inner(turns):
         prev = {}
         for turn, expectation in turns:
-            prev = f(prev, turn)
+            new = f(prev, turn)
             assert (
-                prev[graph.make_computation_node(sink)] == expectation
-            ), f"actual={prev[graph.make_computation_node(sink)]}\n expected: {expectation}"
+                new[graph.make_computation_node(sink)] == expectation
+            ), f"actual={new[graph.make_computation_node(sink)]}\n expected: {expectation}"
+            prev = new
 
     return inner
 

computation_graph/graph_test.py

@@ -611,15 +611,12 @@ def output_node(x):
     )
     graph_runners.unary_with_state_and_expectations(
         composers.compose_left(
-            composers.make_first(
-                composers.make_compose(
-                    composers.compose_left(
-                        skip_or_passthrough, remember_first, key="upstream"
-                    ),
-                    input_node,
-                    key="input",
+            composers.compose_left(
+                input_node,
+                composers.compose_left(
+                    skip_or_passthrough, remember_first, key="upstream"
                 ),
-                lambda: "state skipped",
+                key="input",
             ),
             output_node,
         ),
@@ -628,7 +625,7 @@ def output_node(x):
     )(
         [
             ["remember this", "remember this"],
-            ["skip state", "state skipped"],
+            ["skip state", "remember this"],
             ["recall", "remember this"],
         ]
     )