✨ Add autocomplete support for VS Code, via dataclass_transform (py…

…dantic#2721)

* ✨ Add autocomplete support for VS Code, via dataclass_transform

* 📝 Update changes

* 📝 Add docs for VS Code

* 📝 Clarify strict type error checks alternatives, include example with cast()

* ♻️ Update BaseSettings annotation to improve editor support

keeping editor support for BaseSetting's custom Config, but preventing __config__ from showing in constructor on editors supporting dataclass_transform

* 🎨 Remove unused type: ignore comment

* 🎨 Update type annotations for BaseSettings and BaseModel to use ClassVar where suitable

to improve editor support with type annotations and dataclass_transform

* 🎨 Apply ClassVars again

* 📝 Simplify VS Code docs terms

refer mainly to Pylance and clarify the relationship with Pyright

* 📝 Add link to Pylance FAQ

Co-authored-by: PrettyWood <em.jolibois@gmail.com>

pydantic/main.py

@@ -127,18 +127,6 @@ def hash_function(self_: Any) -> int:
 _is_base_model_class_defined = False
 
 
-_T = TypeVar('_T')
-
-
-def __dataclass_transform__(
-    *,
-    eq_default: bool = True,
-    order_default: bool = False,
-    kw_only_default: bool = False,
-    field_descriptors: Tuple[Union[type, Callable[..., Any]], ...] = (()),
-) -> Callable[[_T], _T]:
-    return lambda a: a
-
 @__dataclass_transform__(kw_only_default=True, field_descriptors=(Field, FieldInfo))
 class ModelMetaclass(ABCMeta):
     @no_type_check  # noqa C901