[Stable] Typechecking edge weights of input graphs to Lattice & Fix copyright after cross-year merge

.pylintdict

@@ -259,6 +259,8 @@ mol
 morse
 mpl
 mul
+multi
+multigraph
 multinomial
 mypy
 namelist

qiskit_nature/problems/second_quantization/lattice/lattices/lattice.py

@@ -1,6 +1,6 @@
 # This code is part of Qiskit.
 #
-# (C) Copyright IBM 2021.
+# (C) Copyright IBM 2021, 2022.
 #
 # This code is licensed under the Apache License, Version 2.0. You may
 # obtain a copy of this license in the LICENSE.txt file in the root directory
@@ -11,11 +11,14 @@
 # that they have been altered from the originals.
 
 """General Lattice."""
+
 from copy import deepcopy
 from dataclasses import asdict, dataclass
 from typing import Callable, List, Optional, Sequence, Tuple, Union
+import numbers
 
 import numpy as np
+
 from retworkx import NodeIndices, PyGraph, WeightedEdgeList, adjacency_matrix
 from retworkx.visualization import mpl_draw
 
@@ -113,17 +116,24 @@ def __init__(self, graph: PyGraph) -> None:
             graph: Input graph for Lattice. `graph.multigraph` must be False.
 
         Raises:
-            ValueError: If `graph.multigraph` is True for a given graph, it is invalid.
+            ValueError: If the input graph is a multigraph.
+            ValueError: If the graph edges are non-numeric.
         """
         if graph.multigraph:
             raise ValueError(
                 f"Invalid `graph.multigraph` {graph.multigraph} is given. "
                 "`graph.multigraph` must be `False`."
             )
-        if graph.edges() == [None] * graph.num_edges():
-            weighted_edges = [edge + (1.0,) for edge in graph.edge_list()]
-            for start, end, weight in weighted_edges:
-                graph.update_edge(start, end, weight)
+
+        # validate the edge weights
+        for edge_index, edge in graph.edge_index_map().items():
+            weight = edge[2]
+            if weight is None or weight == {}:
+                # None or {} is updated to be 1
+                graph.update_edge_by_index(edge_index, 1)
+            elif not isinstance(weight, numbers.Number):
+                raise ValueError(f"Unsupported weight {weight} on edge with index {edge_index}.")
+
         self._graph = graph
 
         self.pos: Optional[dict] = None

releasenotes/notes/lattice-edge-typecheck-3f5b4896fe26c8dc.yaml

@@ -0,0 +1,21 @@
+---
+fixes:
+  - |
+    Add a type check for the input graphs to
+    :class:`~qiskit_nature.problems.second_quantization.lattice.lattices.Lattice`
+    which asserts that the edge weights of the graph are either numeric (or one of `None` or `{}`
+    which is replaced by a unit weight). This prevents possibly unexpected errors in the
+    application stack when an operator is constructed from the lattice.
+
+    In particular, the following now raises a `ValueError`:
+
+    .. code-block:: python
+
+        from retworkx import PyGraph
+        from qiskit_nature.problems.second_quantization.lattice import Lattice
+
+        graph = PyGraph(multigraph=False)
+        graph.add_nodes_from(range(3))
+        graph.add_edges_from([(0, 1, 1), (1, 2, "banana")])  # banana is not a valid weight!
+
+        lattice = Lattice(graph)

test/problems/second_quantization/lattice/lattices/test_lattice.py

@@ -1,6 +1,6 @@
 # This code is part of Qiskit.
 #
-# (C) Copyright IBM 2021.
+# (C) Copyright IBM 2021, 2022.
 #
 # This code is licensed under the Apache License, Version 2.0. You may
 # obtain a copy of this license in the LICENSE.txt file in the root directory
@@ -133,3 +133,29 @@ def test_to_adjacency_matrix(self):
 
         target_matrix = np.array([[0, 1, 1], [1, 0, 0], [1, 0, 1]])
         assert_array_equal(lattice.to_adjacency_matrix(), target_matrix)
+
+    def test_nonnumeric_weight_raises(self):
+        """Test the initialization with a graph with non-numeric edge weights raises."""
+        graph = PyGraph(multigraph=False)
+        graph.add_nodes_from(range(3))
+        graph.add_edges_from([(0, 1, 1), (1, 2, "banana")])
+
+        with self.assertRaises(ValueError):
+            _ = Lattice(graph)
+
+    def test_edges_removed(self):
+        """Test the initialization with a graph where edges have been removed."""
+        graph = PyGraph(multigraph=False)
+        graph.add_nodes_from(range(3))
+        graph.add_edges_from([(0, 1, 1), (1, 2, 1)])
+        graph.remove_edge_from_index(0)
+
+        lattice = Lattice(graph)
+
+        target_graph = PyGraph(multigraph=False)
+        target_graph.add_nodes_from(range(3))
+        target_graph.add_edges_from([(1, 2, 1)])
+
+        self.assertTrue(
+            is_isomorphic(lattice.graph, target_graph, edge_matcher=lambda x, y: x == y)
+        )