Empty string is a valid JSON-key

Signed-off-by: Sergey Tsaplin <me@sergeytsaplin.com>

pydantic/fields.py

@@ -148,7 +148,7 @@ def __init__(self, default: Any = Undefined, **kwargs: Any) -> None:
         self.default = default
         self.default_factory = kwargs.pop('default_factory', None)
         self.alias = kwargs.pop('alias', None)
-        self.alias_priority = kwargs.pop('alias_priority', 2 if self.alias else None)
+        self.alias_priority = kwargs.pop('alias_priority', 2 if self.alias is not None else None)
         self.title = kwargs.pop('title', None)
         self.description = kwargs.pop('description', None)
         self.exclude = kwargs.pop('exclude', None)
@@ -395,7 +395,7 @@ def __init__(
 
         self.name: str = name
         self.has_alias: bool = bool(alias)
-        self.alias: str = alias or name
+        self.alias: str = alias if alias is not None else name
         self.type_: Any = convert_generics(type_)
         self.outer_type_: Any = type_
         self.class_validators = class_validators or {}

tests/test_aliases.py

@@ -335,3 +335,13 @@ def alias_generator(x):
         'd_config_parent',
         'e_generator_child',
     ]
+
+
+def test_empty_string_alias():
+    class Model(BaseModel):
+        empty_string_key: int = Field(alias='')
+
+    data = {'': 123}
+    m = Model(**data)
+    assert m.empty_string_key == 123
+    assert m.dict(by_alias=True) == data