Fix rvs_to_value_vars inplace update bug

pymc/aesaraf.py

@@ -335,7 +335,7 @@ def rvs_to_value_vars(
     initial_replacements: Optional[Dict[TensorVariable, TensorVariable]] = None,
     **kwargs,
 ) -> Tuple[TensorVariable, Dict[TensorVariable, TensorVariable]]:
-    """Replace random variables in graphs with their value variables.
+    """Clone and replace random variables in graphs with their value variables.
 
     This will *not* recompute test values in the resulting graphs.
 
@@ -383,6 +383,16 @@ def transform_replacements(var, replacements):
         # Walk the transformed variable and make replacements
         return [trans_rv_value]
 
+    # Clone original graphs
+    inputs = [i for i in graph_inputs(graphs) if not isinstance(i, Constant)]
+    equiv = clone_get_equiv(inputs, graphs, False, False, {})
+    graphs = [equiv[n] for n in graphs]
+
+    if initial_replacements:
+        initial_replacements = {
+            equiv.get(k, k): equiv.get(v, v) for k, v in initial_replacements.items()
+        }
+
     return replace_rvs_in_graphs(graphs, transform_replacements, initial_replacements, **kwargs)
 
 

pymc/tests/test_aesaraf.py

@@ -23,7 +23,7 @@
 import pytest
 import scipy.sparse as sps
 
-from aesara.graph.basic import Constant, Variable, ancestors
+from aesara.graph.basic import Constant, Variable, ancestors, equal_computations
 from aesara.tensor.random.basic import normal, uniform
 from aesara.tensor.random.op import RandomVariable
 from aesara.tensor.subtensor import AdvancedIncSubtensor, AdvancedIncSubtensor1
@@ -529,3 +529,24 @@ def test_rvs_to_value_vars():
     assert a_value_var in res_ancestors
     assert b_value_var in res_ancestors
     assert c_value_var in res_ancestors
+
+
+def test_rvs_to_value_vars_nested():
+    # Test that calling rvs_to_value_vars in models with nested transformations
+    # does not change the original rvs in place. See issue #5172
+    with pm.Model() as m:
+        one = pm.LogNormal("one", mu=0)
+        two = pm.LogNormal("two", mu=at.log(one))
+
+        # We add potentials or deterministics that are not in topological order
+        pm.Potential("two_pot", two)
+        pm.Potential("one_pot", one)
+
+        before = aesara.clone_replace(m.free_RVs)
+
+        # This call would change the model free_RVs in place in #5172
+        res, _ = rvs_to_value_vars(m.potentials, apply_transforms=True)
+
+        after = aesara.clone_replace(m.free_RVs)
+
+        assert equal_computations(before, after)