added error handling for JSON duplicate IDs

docs/source/api/recipes/recipes.ipynb

@@ -958,21 +958,25 @@
     }
    ],
    "source": [
-    "import xgi\n",
+    "import itertools\n",
+    "\n",
     "import matplotlib.pyplot as plt\n",
-    "from matplotlib import gridspec\n",
     "import numpy as np\n",
-    "import itertools\n",
+    "from matplotlib import gridspec\n",
+    "\n",
+    "import xgi\n",
     "\n",
     "link_color = \"#000000\"\n",
     "triangle_color = \"#648FFF\"\n",
     "square_color = \"#785EF0\"\n",
     "pentagon_color = \"#DC267F\"\n",
     "colors = [link_color, triangle_color, square_color, pentagon_color]\n",
     "\n",
+    "\n",
     "def color_edges(H):\n",
     "    return [colors[i - 2] for i in H.edges.filterby(\"order\", 1, \"gt\").size.aslist()]\n",
     "\n",
+    "\n",
     "links = [[1, 2], [1, 3], [5, 6], [1, 7]]\n",
     "triangles = [[3, 5, 7], [2, 7, 1], [6, 10, 15]]\n",
     "squares = [[7, 8, 9, 10]]\n",

tests/readwrite/test_json.py

@@ -251,3 +251,15 @@ def test_write_json(edgelist1):
     assert H2.nodes[2] == {"name": "Ilya"}
     assert H2.edges[1] == {"weight": 2}
     assert H2["name"] == "test"
+
+    badH = xgi.Hypergraph()
+    # duplicate node IDs when casting to a string
+    badH.add_nodes_from(["2", 2])
+    with pytest.raises(XGIError):
+        xgi.write_json(badH, "test.json")
+
+    badH = xgi.Hypergraph()
+    # duplicate edge IDs when casting to a string
+    badH.add_edges_from({"2": [1, 2, 3], 2: [4, 5, 6]})
+    with pytest.raises(XGIError):
+        xgi.write_json(badH, "test.json")

xgi/readwrite/json.py

@@ -1,5 +1,6 @@
 """Read from and write to JSON."""
 import json
+from collections import Counter
 
 from ..convert import dict_to_hypergraph
 from ..exception import XGIError
@@ -18,6 +19,12 @@ def write_json(H, path):
     path: string
         The path of the file to read from
 
+    Raises
+    ------
+    XGIError
+        If the node or edge IDs have conflicts after casting
+        to strings, e.g., node IDs "2" and 2.
+
     """
     # initialize empty data
     data = {}
@@ -29,11 +36,31 @@ def write_json(H, path):
     # get node data
     try:
         data["node-data"] = {str(idx): H.nodes[idx] for idx in H.nodes}
+
+        if len(data["node-data"]) != H.num_nodes:
+            dups = [
+                item
+                for item, count in Counter([str(n) for n in H.nodes]).items()
+                if count > 1
+            ]
+            raise XGIError(
+                f"When casting node IDs to strings, ID(s) {', '.join(dups)} have conflicting IDs!"
+            )
     except KeyError:
         raise XGIError("Node attributes not saved!")
 
     try:
         data["edge-data"] = {str(idx): H.edges[idx] for idx in H.edges}
+
+        if len(data["edge-data"]) != H.num_edges:
+            dups = [
+                item
+                for item, count in Counter([str(n) for n in H.edges]).items()
+                if count > 1
+            ]
+            raise XGIError(
+                f"When casting edge IDs to strings, ID(s) {', '.join(dups)} have conflicting IDs!"
+            )
     except KeyError:
         raise XGIError("Edge attributes not saved!")