Preserve function default and kwdefault through retry decorator (#406)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

releasenotes/notes/some-slug-for-preserve-defaults-86682846dfa18005.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Preserve __defaults__ and __kwdefaults__ through retry decorator

tenacity/__init__.py

@@ -284,7 +284,7 @@ def wraps(self, f: WrappedFn) -> WrappedFn:
         :param f: A function to wraps for retrying.
         """
 
-        @functools.wraps(f)
+        @functools.wraps(f, functools.WRAPPER_ASSIGNMENTS + ("__defaults__", "__kwdefaults__"))
         def wrapped_f(*args: t.Any, **kw: t.Any) -> t.Any:
             return self(f, *args, **kw)
 

tenacity/_asyncio.py

@@ -83,7 +83,7 @@ def wraps(self, fn: WrappedFn) -> WrappedFn:
         fn = super().wraps(fn)
         # Ensure wrapper is recognized as a coroutine function.
 
-        @functools.wraps(fn)
+        @functools.wraps(fn, functools.WRAPPER_ASSIGNMENTS + ("__defaults__", "__kwdefaults__"))
         async def async_wrapped(*args: t.Any, **kwargs: t.Any) -> t.Any:
             return await fn(*args, **kwargs)
 

tests/test_asyncio.py

@@ -21,6 +21,7 @@
 
 import pytest
 
+import tenacity
 from tenacity import AsyncRetrying, RetryError
 from tenacity import _asyncio as tasyncio
 from tenacity import retry, retry_if_result, stop_after_attempt
@@ -89,6 +90,20 @@ def test_retry_attributes(self):
         assert hasattr(_retryable_coroutine, "retry")
         assert hasattr(_retryable_coroutine, "retry_with")
 
+    def test_retry_preserves_argument_defaults(self):
+        async def function_with_defaults(a=1):
+            return a
+
+        async def function_with_kwdefaults(*, a=1):
+            return a
+
+        retrying = AsyncRetrying(wait=tenacity.wait_fixed(0.01), stop=tenacity.stop_after_attempt(3))
+        wrapped_defaults_function = retrying.wraps(function_with_defaults)
+        wrapped_kwdefaults_function = retrying.wraps(function_with_kwdefaults)
+
+        self.assertEqual(function_with_defaults.__defaults__, wrapped_defaults_function.__defaults__)
+        self.assertEqual(function_with_kwdefaults.__kwdefaults__, wrapped_kwdefaults_function.__kwdefaults__)
+
     @asynctest
     async def test_attempt_number_is_correct_for_interleaved_coroutines(self):
         attempts = []

tests/test_tenacity.py

@@ -1054,6 +1054,20 @@ def test_retry_if_exception_cause_type(self):
         except NameError:
             pass
 
+    def test_retry_preserves_argument_defaults(self):
+        def function_with_defaults(a=1):
+            return a
+
+        def function_with_kwdefaults(*, a=1):
+            return a
+
+        retrying = Retrying(wait=tenacity.wait_fixed(0.01), stop=tenacity.stop_after_attempt(3))
+        wrapped_defaults_function = retrying.wraps(function_with_defaults)
+        wrapped_kwdefaults_function = retrying.wraps(function_with_kwdefaults)
+
+        self.assertEqual(function_with_defaults.__defaults__, wrapped_defaults_function.__defaults__)
+        self.assertEqual(function_with_kwdefaults.__kwdefaults__, wrapped_kwdefaults_function.__kwdefaults__)
+
     def test_defaults(self):
         self.assertTrue(_retryable_default(NoNameErrorAfterCount(5)))
         self.assertTrue(_retryable_default_f(NoNameErrorAfterCount(5)))