Simplify FunctionTask wrapper handling with functools.update_wrapper

changes/pr4608.yaml

@@ -0,0 +1,3 @@
+
+enhancement:
+  - "Use `functools.update_wrapper` for `FunctionTask` - [#4608](https://github.com/PrefectHQ/prefect/pull/4608)"

src/prefect/tasks/core/function.py

@@ -6,32 +6,19 @@
 """
 
 from typing import Any, Callable
+from functools import update_wrapper
 
 import prefect
 
 
-class _DocProxy(object):
-    """A descriptor that proxies through the docstring for the wrapped task as
-    the docstring for a `FunctionTask` instance."""
-
-    def __init__(self, cls_doc):
-        self._cls_doc = cls_doc
-
-    def __get__(self, obj, cls):
-        if obj is None:
-            return self._cls_doc
-        else:
-            return getattr(obj.run, "__doc__", None) or self._cls_doc
-
-
 class FunctionTask(prefect.Task):
-    __doc__ = _DocProxy(
-        """A convenience Task for functionally creating Task instances with
+    """A convenience Task for functionally creating Task instances with
     arbitrary callable `run` methods.
 
     Args:
         - fn (callable): the function to be the task's `run` method
-        - name (str, optional): the name of this task
+        - name (str, optional): the name of this task; if not provided it is inferred
+            as the function name
         - **kwargs: keyword arguments that will be passed to the Task
             constructor
 
@@ -47,26 +34,17 @@ class FunctionTask(prefect.Task):
         result = task(42)
     ```
     """
-    )
 
     def __init__(self, fn: Callable, name: str = None, **kwargs: Any):
         if not callable(fn):
-            raise TypeError("fn must be callable.")
+            raise TypeError("`fn` must be callable")
 
-        # set the name from the fn
+        # Set the Prefect name from the function
         if name is None:
             name = getattr(fn, "__name__", type(self).__name__)
 
-        prefect.core.task._validate_run_signature(fn)  # type: ignore
+        prefect.core.task._validate_run_signature(fn)
         self.run = fn
+        update_wrapper(self, fn)
 
         super().__init__(name=name, **kwargs)
-
-    def __getattr__(self, k):
-        if k == "__wrapped__":
-            return self.run
-        raise AttributeError(
-            f"'FunctionTask' object has no attribute {k}."
-            " Did you call this object within a function that should have been"
-            "decorated with @prefect.task?"
-        )

tests/tasks/core/test_core.py

@@ -58,9 +58,9 @@ def my_fn():
         f = FunctionTask(fn=my_fn)
         assert f.__doc__ == my_fn.__doc__
 
-        # Except when no docstring on wrapped function
+        # Lambdas do not have a function docstring
         f = FunctionTask(fn=lambda x: x + 1)
-        assert "FunctionTask" in f.__doc__
+        assert f.__doc__ is None
 
     def test_function_task_sets__wrapped__(self):
         def my_fn():
@@ -77,12 +77,12 @@ def my_fn():
             pass
 
         t = FunctionTask(fn=my_fn)
-        with pytest.raises(AttributeError) as exc:
+        with pytest.raises(
+            AttributeError,
+            match="'FunctionTask' object has no attribute 'unknown_attribute'",
+        ):
             t.unknown_attribute
 
-        assert "unknown_attribute" in str(exc.value)
-        assert "@prefect.task" in str(exc.value)
-
 
 class TestCollections:
     def test_list_returns_a_list(self):