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fix(graph_search): avoid KeyError in BFS when a node has no outgoing edges - #506
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…edges find_shortest_path_bfs indexed self.graph[value] directly while expanding the queue. Any node reachable in the graph but not present as a key (a leaf node with no outgoing edges, as in a typical adjacency list) raised a KeyError instead of being treated as having no neighbors. The DFS methods already handle this correctly via self.graph.get(start, []); bring BFS in line with that and add a regression test.
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find_shortest_path_bfsindexedself.graph[value]directly while expanding the BFS queue. Any node that is reachable in the graph but is not present as a dict key — a leaf node with no outgoing edges, which is normal for an adjacency-list graph — raised aKeyErrorinstead of being treated as having no neighbors.The other traversal methods on this class (
find_path_dfs,find_all_paths_dfs,find_shortest_path_dfs) already handle this correctly viaself.graph.get(start, []). This bringsfind_shortest_path_bfsin line with them.Repro before the fix:
Added a regression test (
tests/test_graph_search.py) that fails before this change and passes after.Ran the full suite locally with the new test passing. Also ran
codespell,flake8,isort,black --check, andmypyon the changed files with no issues.