Async pipe decorator: preserve wrapped func signature

Author: MetRonnie

cylc/flow/async_util.py

@@ -17,6 +17,7 @@
 
 import asyncio
 from functools import partial, wraps
+from inspect import signature
 import os
 from pathlib import Path
 from typing import List, Union
@@ -262,10 +263,22 @@ def __str__(self):
     def __repr__(self):
         return _AsyncPipe(self.func).__repr__()
 
+    @property
+    def __name__(self):
+        return self.func.__name__
+
     @property
     def __doc__(self):
         return self.func.__doc__
 
+    @property
+    def __signature__(self):
+        return signature(self.func)
+
+    @property
+    def __annotations__(self):
+        return self.func.__annotations__
+
 
 def pipe(func=None, preproc=None):
     """An asynchronous pipe implementation in pure Python.

tests/unit/test_async_util.py

@@ -15,6 +15,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import asyncio
+from inspect import signature
 import logging
 from pathlib import Path
 from random import random
@@ -209,14 +210,17 @@ def test_pipe_brackets():
 
 
 @pipe
-async def documented(x):
+async def documented(x: str, y: int = 0):
     """The docstring for the pipe function."""
     pass
 
 
 def test_documentation():
-    """It should preserve the docstring of pipe functions."""
+    """It should preserve the docstring, signature & annotations of
+    the wrapped function."""
     assert documented.__doc__ == 'The docstring for the pipe function.'
+    assert documented.__annotations__ == {'x': str, 'y': int}
+    assert str(signature(documented)) == '(x: str, y: int = 0)'
 
 
 def test_rewind():