fix(export): stabilize graph JSON collection order

graphify/export.py

@@ -292,6 +292,10 @@ def to_json(G: nx.Graph, communities: dict[int, list[str]], output_path: str, *,
         data = json_graph.node_link_data(G, edges="links")
     except TypeError:
         data = json_graph.node_link_data(G)
+
+    def _json_sort_key(item: dict) -> str:
+        return json.dumps(item, ensure_ascii=False, sort_keys=True, separators=(",", ":"))
+
     for node in data["nodes"]:
         cid = node_community.get(node["id"])
         node["community"] = cid
@@ -311,6 +315,8 @@ def to_json(G: nx.Graph, communities: dict[int, list[str]], output_path: str, *,
         if true_src is not None and true_tgt is not None:
             link["source"] = true_src
             link["target"] = true_tgt
+    data["nodes"].sort(key=_json_sort_key)
+    data["links"].sort(key=_json_sort_key)
     if "hyperedges" not in getattr(G, "graph", {}):
         # Hardening (#2485): a graph with NO hyperedges key at all was built by
         # a path that never engaged hyperedge metadata — distinct from an
@@ -339,7 +345,10 @@ def to_json(G: nx.Graph, communities: dict[int, list[str]], output_path: str, *,
                 f"extraction if this is unexpected.",
                 file=sys.stderr,
             )
-    data["hyperedges"] = getattr(G, "graph", {}).get("hyperedges", [])
+    hyperedges = sorted(getattr(G, "graph", {}).get("hyperedges", []), key=_json_sort_key)
+    if isinstance(data.get("graph"), dict) and "hyperedges" in data["graph"]:
+        data["graph"]["hyperedges"] = hyperedges
+    data["hyperedges"] = hyperedges
     commit = built_at_commit if built_at_commit is not None else _git_head()
     if commit:
         data["built_at_commit"] = commit

tests/test_export.py

@@ -40,6 +40,38 @@ def test_to_json_nodes_have_community():
         for node in data["nodes"]:
             assert "community" in node
 
+
+def test_to_json_sorts_graph_collections_across_insertion_order(tmp_path):
+    import networkx as nx
+
+    nodes = [("b", {"label": "Beta"}), ("a", {"label": "Alpha"}), ("c", {"label": "Gamma"})]
+    links = [
+        ("b", "c", {"relation": "uses", "_src": "b", "_tgt": "c"}),
+        ("a", "b", {"relation": "calls", "_src": "a", "_tgt": "b"}),
+    ]
+    hyperedges = [
+        {"id": "h2", "nodes": ["b", "c"]},
+        {"id": "h1", "nodes": ["a", "b"]},
+    ]
+
+    def make_graph(reverse=False):
+        graph = nx.Graph()
+        graph.add_nodes_from(reversed(nodes) if reverse else nodes)
+        graph.add_edges_from(reversed(links) if reverse else links)
+        graph.graph["hyperedges"] = list(reversed(hyperedges)) if reverse else hyperedges
+        return graph
+
+    outputs = [tmp_path / "first.json", tmp_path / "second.json"]
+    for output, reverse in zip(outputs, (False, True)):
+        assert to_json(
+            make_graph(reverse),
+            {0: ["a", "b"], 1: ["c"]},
+            str(output),
+            built_at_commit="fixed",
+        )
+
+    assert outputs[0].read_bytes() == outputs[1].read_bytes()
+
 def test_to_cypher_creates_file():
     G = make_graph()
     with tempfile.TemporaryDirectory() as tmp: