Add support for field alias in dataclass signature (#8387)

pydantic/_internal/_constructor_signature_generators.py

@@ -10,6 +10,21 @@
     from ..fields import FieldInfo
 
 
+def _field_name_or_alias(field_name: str, field_info: FieldInfo) -> str:
+    """Extract the correct name to use for the field when generating a signature.
+    If it has a valid alias then returns its alais, else returns its name
+    Args:
+        field_name: The name of the field
+        field_info: The field
+
+    Returns:
+        The correct name to use when generating a signature.
+    """
+    return (
+        field_info.alias if isinstance(field_info.alias, str) and is_valid_identifier(field_info.alias) else field_name
+    )
+
+
 def generate_pydantic_signature(
     init: Callable[..., None],
     fields: dict[str, FieldInfo],
@@ -37,6 +52,9 @@ def generate_pydantic_signature(
     for param in islice(present_params, 1, None):  # skip self arg
         # inspect does "clever" things to show annotations as strings because we have
         # `from __future__ import annotations` in main, we don't want that
+        if fields.get(param.name):
+            param_name = _field_name_or_alias(param.name, fields[param.name])
+            param = param.replace(name=param_name)
         if param.annotation == 'Any':
             param = param.replace(annotation=Any)
         if param.kind is param.VAR_KEYWORD:
@@ -48,16 +66,13 @@ def generate_pydantic_signature(
         allow_names = config_wrapper.populate_by_name
         for field_name, field in fields.items():
             # when alias is a str it should be used for signature generation
-            if isinstance(field.alias, str):
-                param_name = field.alias
-            else:
-                param_name = field_name
+            param_name = _field_name_or_alias(field_name, field)
 
             if field_name in merged_params or param_name in merged_params:
                 continue
 
             if not is_valid_identifier(param_name):
-                if allow_names and is_valid_identifier(field_name):
+                if allow_names:
                     param_name = field_name
                 else:
                     use_var_kw = True

tests/test_dataclasses.py

@@ -2487,9 +2487,10 @@ class Model:
         a: float = dataclasses.field(default_factory=float)
         b: float = Field(default=1.0)
         c: float = Field(default_factory=float)
+        d: int = dataclasses.field(metadata={'alias': 'dd'}, default=1)
 
     assert str(inspect.signature(Model)) == (
-        "(x: int, y: str = 'y', z: float = 1.0, a: float = <factory>, b: float = 1.0, c: float = <factory>) -> None"
+        "(x: int, y: str = 'y', z: float = 1.0, a: float = <factory>, b: float = 1.0, c: float = <factory>, dd: int = 1) -> None"
     )