handle JSON serialisation with compound keys

autoconf/dictable.py

@@ -10,7 +10,6 @@
 
 logger = logging.getLogger(__name__)
 
-
 np_type_map = {
     "bool": "bool_",
 }
@@ -47,6 +46,22 @@ def is_array(obj) -> bool:
         return False
 
 
+def compound_key_dict(obj):
+    """
+    Converts a dictionary with compound keys to a dictionary with a single key.
+    """
+    return {
+        "type": "compound_dict",
+        "arguments": [
+            {
+                "key": to_dict(key),
+                "value": to_dict(value),
+            }
+            for key, value in obj.items()
+        ],
+    }
+
+
 def to_dict(obj, filter_args: Tuple[str, ...] = ()) -> dict:
     if isinstance(obj, (int, float, str, bool, type(None))):
         return obj
@@ -101,14 +116,20 @@ def to_dict(obj, filter_args: Tuple[str, ...] = ()) -> dict:
     if isinstance(obj, tuple):
         return {"type": "tuple", "values": list(map(to_dict, obj))}
     if isinstance(obj, dict):
-        return {
+        result = {
             "type": "dict",
             "arguments": {
                 key: to_dict(value)
                 for key, value in obj.items()
                 if key not in filter_args
             },
         }
+        try:
+            json.dumps(result)
+            return result
+        except TypeError:
+            return compound_key_dict(obj)
+
     if obj.__class__.__name__ == "method":
         return to_dict(obj())
     if obj.__class__.__module__ == "builtins":
@@ -297,7 +318,15 @@ def from_dict(dictionary, **kwargs):
     if type_ == "tuple":
         return tuple(map(from_dict, dictionary["values"]))
     if type_ == "dict":
-        return {key: from_dict(value, **kwargs) for key, value in dictionary.items()}
+        return {
+            key: from_dict(value, **kwargs)
+            for key, value in dictionary["arguments"].items()
+        }
+    if type_ == "compound_dict":
+        return {
+            from_dict(item["key"], **kwargs): from_dict(item["value"], **kwargs)
+            for item in dictionary["arguments"]
+        }
 
     if type_ == "type":
         return get_class(dictionary["class_path"])

test_autoconf/test_dictable.py

@@ -192,3 +192,10 @@ def test_int64_slice():
             )
         )
     )
+
+
+def test_compound_key():
+    d = {(1, 2): 1}
+
+    string = json.dumps(to_dict(d))
+    assert d == from_dict(json.loads(string))