netcmd: add custom json encoder for object type fields

The custom JSONEncoder class is also capable of encoding Dn objects to
str, and any object that has a __json__ method.

The __json__ method is not an official dunder method, but this has
been used by other frameworks too (like Pyramid).

Signed-off-by: Rob van der Linde <rob@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>

python/samba/netcmd/encoders.py

@@ -0,0 +1,49 @@
+# Unix SMB/CIFS implementation.
+#
+# encoders: JSONEncoder class for dealing with object fields.
+#
+# Copyright (C) Catalyst.Net Ltd. 2023
+#
+# Written by Rob van der Linde <rob@catalyst.net.nz>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+import json
+from datetime import datetime
+from decimal import Decimal
+from enum import Enum
+
+from ldb import Dn
+
+
+class JSONEncoder(json.JSONEncoder):
+    """Custom JSON encoder class to help out with some data types.
+
+    For example, the json module has no idea how to encode a Dn object to str.
+    Another common object that is handled is Decimal types.
+
+    In addition, any objects that have a __json__ method will get called.
+    """
+
+    def default(self, obj):
+        if isinstance(obj, (Decimal, Dn)):
+            return str(obj)
+        elif isinstance(obj, Enum):
+            return str(obj.value)
+        elif isinstance(obj, datetime):
+            return obj.isoformat()
+        elif getattr(obj, "__json__", None) and callable(obj.__json__):
+            return obj.__json__()
+        return obj