Fail gracefully in unconditional_constant_fold if Op can't be evaluated at all

pytensor/tensor/rewriting/basic.py

@@ -1165,9 +1165,13 @@ def unconditional_constant_folding(fgraph, node):
         )
         required = thunk()
     except NotImplementedError:
-        # Not all Ops have a python implementation
-        thunk = node.op.make_thunk(node, storage_map, compute_map, no_recycling=[])
-        required = thunk()
+        try:
+            # Not all Ops have a python implementation
+            thunk = node.op.make_thunk(node, storage_map, compute_map, no_recycling=[])
+            required = thunk()
+        except NotImplementedError:
+            # And some Ops (like dummy Ops) can never be evaluated
+            return None
 
     # A node whose inputs are all provided should always return successfully
     assert not required

tests/tensor/rewriting/test_basic.py

@@ -784,10 +784,11 @@ class TestConstantFolding:
 
         fg = FunctionGraph(outputs=[out], clone=False)
         # Default constant_folding will raise
-        with pytest.raises(NotImplementedError):
-            topo_constant_folding.apply(fg)
+        topo_constant_folding.apply(fg)
+        assert not isinstance(fg.outputs[0], Constant)
+        assert isinstance(fg.outputs[0].owner.op, OpNoPerform)
 
-        # Unconditional constant folding will be silent
+        # Default and Unconditional constant folding will be silent
         topo_unconditional_constant_folding.apply(fg)
         assert not isinstance(fg.outputs[0], Constant)
         assert isinstance(fg.outputs[0].owner.op, OpNoPerform)