lidatong#305: Split dataclass parser and field value parser

dataclasses_json/core.py

@@ -172,41 +172,38 @@ def _decode_dataclass(cls, kvs, infer_missing):
             init_kwargs[field.name] = field_value
             continue
 
-        while True:
-            if not _is_new_type(field_type):
-                break
+        init_kwargs[field.name] = _decode_field(field_type, field_value, infer_missing=infer_missing, override=overrides.get(field.name, None))
 
-            field_type = field_type.__supertype__
+    return cls(**init_kwargs)
 
-        if (field.name in overrides
-                and overrides[field.name].decoder is not None):
-            # FIXME hack
-            if field_type is type(field_value):
-                init_kwargs[field.name] = field_value
-            else:
-                init_kwargs[field.name] = overrides[field.name].decoder(
-                    field_value)
-        elif is_dataclass(field_type):
-            # FIXME this is a band-aid to deal with the value already being
-            # serialized when handling nested marshmallow schema
-            # proper fix is to investigate the marshmallow schema generation
-            # code
-            if is_dataclass(field_value):
-                value = field_value
-            else:
-                value = _decode_dataclass(field_type, field_value,
-                                          infer_missing)
-            init_kwargs[field.name] = value
-        elif _is_supported_generic(field_type) and field_type != str:
-            init_kwargs[field.name] = _decode_generic(field_type,
-                                                      field_value,
-                                                      infer_missing)
-        else:
-            init_kwargs[field.name] = _support_extended_types(field_type,
-                                                              field_value)
 
-    return cls(**init_kwargs)
+def _decode_field(field_type, field_value, *, infer_missing: bool, override = None):
+    while True:
+        if not _is_new_type(field_type):
+            break
 
+        field_type = field_type.__supertype__
+
+    if (override is not None and override.decoder is not None):
+        # FIXME hack
+        if field_type is type(field_value):
+            return field_value
+        else:
+            return override.decoder(field_value)
+    elif is_dataclass(field_type):
+        # FIXME this is a band-aid to deal with the value already being
+        # serialized when handling nested marshmallow schema
+        # proper fix is to investigate the marshmallow schema generation
+        # code
+        if is_dataclass(field_value):
+            value = field_value
+        else:
+            value = _decode_dataclass(field_type, field_value, infer_missing=infer_missing)
+        return value
+    elif _is_supported_generic(field_type) and field_type != str:
+        return _decode_generic(field_type, field_value, infer_missing=infer_missing)
+    else:
+        return _support_extended_types(field_type, field_value)
 
 def _support_extended_types(field_type, field_value):
     if _issubclass_safe(field_type, datetime):