Add typed Protocols for FFI capsule exports (part of #1577)

Adds TableFunctionExportable, ExtensionOptionsExportable, and
TaskContextProviderExportable Protocol classes describing the
PyCapsule dunder methods DataFusion's Rust side already expects,
following the existing TableProviderExportable pattern. No runtime
behavior changes.

Author: stantheman0128

python/datafusion/context.py

@@ -145,6 +145,29 @@ class PhysicalOptimizerRuleExportable(Protocol):
     def __datafusion_physical_optimizer_rule__(self) -> object: ...  # noqa: D105
 
 
+class ExtensionOptionsExportable(Protocol):
+    """Type hint for object that has __datafusion_extension_options__ PyCapsule.
+
+    The method returns a PyCapsule wrapping an ``FFI_ExtensionOptions``,
+    typically produced by a separate compiled extension and consumed by
+    :py:meth:`SessionConfig.with_extension`.
+    """
+
+    def __datafusion_extension_options__(self) -> object: ...  # noqa: D105
+
+
+class TaskContextProviderExportable(Protocol):
+    """Type hint for object that has __datafusion_task_context_provider__ PyCapsule.
+
+    The method returns a PyCapsule wrapping an ``FFI_TaskContextProvider``.
+    :py:class:`SessionContext` exposes one for its own task context; a
+    separate compiled extension can decode it (or one of its own) using
+    the matching Rust-side ``from_pycapsule`` helper.
+    """
+
+    def __datafusion_task_context_provider__(self) -> object: ...  # noqa: D105
+
+
 class SessionConfig:
     """Session configuration options."""
 
@@ -337,12 +360,14 @@ def set(self, key: str, value: str) -> SessionConfig:
         self.config_internal = self.config_internal.set(key, value)
         return self
 
-    def with_extension(self, extension: Any) -> SessionConfig:
+    def with_extension(self, extension: ExtensionOptionsExportable) -> SessionConfig:
         """Create a new configuration using an extension.
 
         Args:
             extension: A custom configuration extension object. These are
-            shared from another DataFusion extension library.
+            shared from another DataFusion extension library. It must expose
+            an ``__datafusion_extension_options__`` PyCapsule, see
+            :py:class:`ExtensionOptionsExportable`.
 
         Returns:
             A new :py:class:`SessionConfig` object with the updated setting.

python/datafusion/user_defined.py

@@ -1121,6 +1121,15 @@ def adapter(*args: Any, session: Any, **kwargs: Any) -> Any:
     return adapter
 
 
+class TableFunctionExportable(Protocol):
+    """Type hint for object that has __datafusion_table_function__ PyCapsule.
+
+    https://datafusion.apache.org/python/user-guide/io/table_provider.html
+    """
+
+    def __datafusion_table_function__(self, session: Any) -> object: ...  # noqa: D105
+
+
 class TableFunction:
     """Class for performing user-defined table functions (UDTF).
 
@@ -1131,7 +1140,7 @@ class TableFunction:
     def __init__(
         self,
         name: str,
-        func: Callable[..., Any],
+        func: Callable[..., Any] | TableFunctionExportable,
         ctx: SessionContext | None = None,
         *,
         with_session: bool = False,
@@ -1190,6 +1199,10 @@ def udtf(
         with_session: bool = False,
     ) -> TableFunction: ...
 
+    @overload
+    @staticmethod
+    def udtf(func: TableFunctionExportable, name: str) -> TableFunction: ...
+
     @staticmethod
     def udtf(*args: Any, with_session: bool = False, **kwargs: Any):
         """Create a new User-Defined Table Function (UDTF).