Fixes replacement of dict keys (spcl#1845)

If the internal method `SDFG._replace_dict_keys` is called with the same
`old` and `new` keys, then the method erroneously removes the entry for
the specific key completely. Such a case occurs when calling
`SDFG.replace_dict` with a dictionary that contains identity replacement
matches.

This PR addresses the issue by:
- [x] Adding a check inside `SDFG._replace_dict_keys` and skipping if
`old == new`. A warning is also thrown for debugging purposes.
- [x] Removing identity replacement matches from `repldict` and
`symrepl` in `SDFG.replace_dict`.

dace/sdfg/sdfg.py

@@ -102,6 +102,9 @@ def _nested_arrays_from_json(obj, context=None):
 
 
 def _replace_dict_keys(d, old, new):
+    if old == new:
+        warnings.warn(f"Trying to replace key with the same name {old} ... skipping.")
+        return
     if old in d:
         if new in d:
             warnings.warn('"%s" already exists in SDFG' % new)
@@ -734,6 +737,12 @@ def replace_dict(self,
         :param replace_in_graph: Whether to replace in SDFG nodes / edges.
         :param replace_keys: If True, replaces in SDFG property names (e.g., array, symbol, and constant names).
         """
+
+        repldict = {k: v for k, v in repldict.items() if k != v}
+        if symrepl:
+            symrepl = {k: v for k, v in symrepl.items() if str(k) != str(v)}
+
+
         symrepl = symrepl or {
             symbolic.pystr_to_symbolic(k): symbolic.pystr_to_symbolic(v) if isinstance(k, str) else v
             for k, v in repldict.items()

tests/sdfg/interstate_assignment_test.py

@@ -0,0 +1,36 @@
+# Copyright 2019-2025 ETH Zurich and the DaCe authors. All rights reserved.
+
+import dace
+import numpy as np
+
+
+def test_key_replacement_same_name():
+
+    sdfg = dace.SDFG('key_replacement_same_name')
+    sdfg.add_array('inp', [1], dace.int32)
+    sdfg.add_array('out', [1], dace.int32)
+
+    first = sdfg.add_state('first_state')
+    second = sdfg.add_state('second_state')
+    edge = sdfg.add_edge(first, second, dace.InterstateEdge(assignments={'s': 'inp[0]'}))
+
+    task = second.add_tasklet('t', {}, {'__out'}, '__out = s')
+    access = second.add_access('out')
+    second.add_edge(task, '__out', access, None, dace.Memlet('out[0]'))
+
+    sdfg.replace('s', 's')
+    assert 's' in edge.data.assignments
+    sdfg.replace_dict({'s': 's'})
+    assert 's' in edge.data.assignments
+
+    rng = np.random.default_rng()
+    inp = rng.integers(1, 100, 1)
+    inp = np.array(inp, dtype=np.int32)
+    out = np.zeros([1], dtype=np.int32)
+
+    sdfg(inp=inp, out=out)
+    assert out[0] == inp[0]
+
+
+if __name__ == '__main__':
+    test_key_replacement_same_name()