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Fix solve endpoint accepting disconnected directed graphs #3

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Merged
R3Dzf merged 2 commits into from
Oct 12, 2026
Merged

Fix solve endpoint accepting disconnected directed graphs #3

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d378ea1
fix: reject disconnected graphs consistently in solve endpoint
R3Dzf Oct 12, 2026
645fd2a
test: ensure solve rejects disconnected and reverse-only graphs
R3Dzf Oct 12, 2026
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5 changes: 5 additions & 0 deletions app.py
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Original file line number Diff line number Diff line change
Expand Up @@ -219,6 +219,11 @@ def solve_diagram(data: DiagramData):
return {"status": "error", "message": f"Input node '{data.input_node}' not found."}
if data.output_node not in real_nodes:
return {"status": "error", "message": f"Output node '{data.output_node}' not found."}
if not nx.has_path(G, data.input_node, data.output_node):
return {
"status": "error",
"message": f"No forward path from '{data.input_node}' to '{data.output_node}'.",
}

raw_loops = list(nx.simple_cycles(G))
loops_data = []
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20 changes: 20 additions & 0 deletions tests/test_solver.py
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Original file line number Diff line number Diff line change
Expand Up @@ -95,6 +95,26 @@ def test_validate_rejects_missing_output_node(self):
self.assertEqual(result["status"], "error")
self.assertIn("missing_output_node", {e["type"] for e in result["errors"]})

def test_solve_rejects_disconnected_output(self):
data = diagram(
[("S", "A", "G")],
nodes=["S", "A", "T"],
)
validated = validate_diagram(data)
solved = solve_diagram(data)
self.assertEqual(validated["status"], "error")
self.assertIn("no_path", {error["type"] for error in validated["errors"]})
self.assertEqual(solved["status"], "error")
self.assertIn("No forward path", solved["message"])
self.assertNotIn("transfer_function_expr", solved)

def test_solve_rejects_reverse_only_connection(self):
data = diagram([("T", "S", "H")])
self.assertEqual(validate_diagram(data)["status"], "error")
solved = solve_diagram(data)
self.assertEqual(solved["status"], "error")
self.assertIn("No forward path", solved["message"])

def test_validate_reports_off_path_and_isolated_nodes(self):
result = validate_diagram(
diagram([("S", "T", "G")], nodes=["S", "T", "Z"])
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