tools (utils): Add maybe_async function:

`maybe_async` can be used to call a function which may be or not `async`. It doesn't use
`defer.ensureDeferred` contrary to `ad_defered`, so the call stack is not lost, and it's
easier to debug when an Exception is raised.

libervia/backend/tools/utils.py

@@ -18,7 +18,7 @@
 
 """various useful methods"""
 
-from typing import Optional, Union
+from typing import Any, Optional, Union
 import unicodedata
 import os.path
 import datetime
@@ -92,12 +92,13 @@ def partial(func, *fixed_args, **fixed_kwargs):
 
     return method
 
-
-def as_deferred(func, *args, **kwargs):
+def as_deferred(func, *args, **kwargs) -> defer.Deferred:
     """Call a method and return a Deferred
 
     the method can be a simple callable, a Deferred or a coroutine.
-    It is similar to defer.maybeDeferred, but also handles coroutines
+    It is similar to defer.maybeDeferred, but also handles coroutines.
+    Due to the use of ``defer.ensureDeferred``, the call stack may be lost, which can make
+    debugging harder in case of Exception, the function ``maybe_async`` below solves this.
     """
     try:
         ret = func(*args, **kwargs)
@@ -114,6 +115,26 @@ def as_deferred(func, *args, **kwargs):
             return defer.succeed(ret)
 
 
+async def maybe_async(ret: Any) -> Any:
+    """Check if a return value is awaitable and await it if necessary.
+
+    This function checks whether the return value of a method is awaitable. If it is, the
+    function awaits on it and returns the awaited value. Otherwise, it returns the value
+    as-is.
+
+    Unlike ``as_deferred``, this function does not call ``defer.ensureDeferred``, so it
+    must be used within an already ``async`` context where ``defer.ensureDeferred`` has
+    already been called at a higher level. This makes debugging easier by preserving the
+    call stack in case of exceptions.
+
+    @param ret: The return value of a function, which may be awaitable or not.
+    @return: The awaited value if the input was awaitable, otherwise the input as-is.
+    """
+    if inspect.isawaitable(ret):
+        return await ret
+    return ret
+
+
 def aio(func):
     """Decorator to return a Deferred from asyncio coroutine