basic orjson serialize, json.dumps fallback

my/core/common.py

@@ -531,7 +531,13 @@ def test_guess_datetime() -> None:
     # TODO test @property?
 
 
-def asdict(thing) -> Json:
+def is_namedtuple(thing: Any) -> bool:
+    # basic check to see if this is a namedtuple-like
+    _asdict = getattr(thing, '_asdict', None)
+    return _asdict and callable(_asdict)
+
+
+def asdict(thing: Any) -> Json:
     # todo primitive?
     # todo exception?
     if isinstance(thing, dict):
@@ -539,9 +545,9 @@ def asdict(thing) -> Json:
     import dataclasses as D
     if D.is_dataclass(thing):
         return D.asdict(thing)
-    # must be a NT otherwise?
-    # todo add a proper check.. ()
-    return thing._asdict()
+    if is_namedtuple(thing):
+        return thing._asdict()
+    raise TypeError(f'Could not convert object {thing} to dict')
 
 
 # todo not sure about naming

my/core/serialize.py

@@ -0,0 +1,40 @@
+from typing import Any
+
+from .common import is_namedtuple
+from .error import error_to_json
+
+# note: it would be nice to combine the 'asdict' and _orjson_default to some function
+# that takes a complex python object and returns JSON-compatible fields, while still
+# being a dictionary.
+# a workaround is to encode with dumps below and then json.loads it immediately
+
+
+def _orjson_default(obj: Any) -> Any:
+    """
+    Encodes complex python datatypes to simpler representations,
+    before they're serialized to JSON string
+    """
+    # orjson doesn't serialize namedtuples to avoid serializing
+    # them as tuples (arrays), since they're technically a subclass
+    if is_namedtuple(obj):
+        return obj._asdict()
+    if isinstance(obj, Exception):
+        err = error_to_json(obj)
+        # remove unrelated dt key? maybe error_to_json should be refactored?
+        err.pop('dt', None)
+        return err
+    raise TypeError(f"Could not serialize object of type {obj.__type__.__name__}")
+
+
+def dumps(obj: Any) -> str:
+    try:
+        import orjson
+        # serialize 'b'"1970-01-01T00:00:00"' instead of b'"1970-01-01T00:00:00.000000"
+        opts = orjson.OPT_OMIT_MICROSECONDS
+        json_bytes = orjson.dumps(obj, default=_orjson_default, option=opts)
+        return json_bytes.decode('utf-8')
+    except ModuleNotFoundError:
+        import warnings
+        warnings.warn("You might want to install 'orjson' to support serialization for lots more types!")
+        import json
+        return json.dumps(obj, default=_orjson_default)