[enh] Implement an extended JSON encoder and support sets

moulinette/interfaces/api.py

@@ -16,6 +16,7 @@ from bottle import run, request, response, Bottle, HTTPResponse
 
 from moulinette.core import MoulinetteError, clean_session
 from moulinette.interfaces import (BaseActionsMapParser, BaseInterface)
+from moulinette.utils.serialize import JSONExtendedEncoder
 
 logger = logging.getLogger('moulinette.interface.api')
 
@@ -462,7 +463,7 @@ def format_for_response(content):
 
     # Return JSON-style response
     response.content_type = 'application/json'
-    return json_encode(content)
+    return json_encode(content, cls=JSONExtendedEncoder)
 
 
 # API Classes Implementation -------------------------------------------

moulinette/interfaces/cli.py

@@ -48,6 +48,8 @@ def pretty_print_dict(d, depth=0):
     """
     for k,v in sorted(d.items(), key=lambda x: x[0]):
         k = colorize(str(k), 'purple')
+        if isinstance(v, (tuple, set)):
+            v = list(v)
         if isinstance(v, list) and len(v) == 1:
             v = v[0]
         if isinstance(v, dict):
@@ -202,7 +204,8 @@ class Interface(BaseInterface):
         # Format and print result
         if print_json:
             import json
-            print(json.dumps(ret))
+            from moulinette.utils.serialize import JSONExtendedEncoder
+            print(json.dumps(ret, cls=JSONExtendedEncoder))
         elif isinstance(ret, dict):
             pretty_print_dict(ret)
         else:

moulinette/utils/serialize.py

@@ -0,0 +1,29 @@
+import logging
+from json.encoder import JSONEncoder
+
+logger = logging.getLogger('moulinette.utils.serialize')
+
+
+# JSON utilities -------------------------------------------------------
+
+class JSONExtendedEncoder(JSONEncoder):
+    """Extended JSON encoder
+
+    Extend default JSON encoder to recognize more types and classes. It
+    will never raise if the object can't be encoded and return its repr
+    instead.
+    The following objects and types are supported:
+        - set: converted into list
+
+    """
+    def default(self, o):
+        """Return a serializable object"""
+        # Convert compatible containers into list
+        if isinstance(o, set) or (
+            hasattr(o, '__iter__') and hasattr(o, 'next')):
+            return list(o)
+
+        # Return the repr for object that json can't encode
+        logger.warning('cannot properly encode in JSON the object %s, '
+                       'returned repr is: %r', type(o), o)
+        return repr(o)