Improved cross-language homogeneity (#34)

Use an explicit "handle" method on Function instances, as this is the
most similar method signature approach between different language; a
primary goal of the project.  This is in contrast to a more strict
adherence to the ASGI spec which would see the Function object itself be
callable.  See PR for further exploration of this choice.

Author: lkingland

CHANGELOG.md

@@ -10,6 +10,9 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ### Added
 ### Changed
+
+- Simplified instanced functions by expecting a named 'handle' method.
+
 ### Deprecated
 ### Removed
 ### Fixed
@@ -19,13 +22,15 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ## [0.2.0] - 2024-11-06
 
 ### Added
+
 - optional message returns from lifeycle methods "alive" and "ready"
 - expanded development and release documentation
 
 
 ## [0.1.0] - 2024-10-28
 
 ### Added
+
 - Initial Implementation of the Python HTTP Functions Middleware
 
 

cmd/fhttp/main.py

@@ -38,9 +38,11 @@ async def handle(scope, receive, send):
 
 # Example instanced handler
 # This is the default expected by this test.
-# The class can be named anything.  See "new" below.
+# The class can be named anything, but there must be a constructor named "new"
+# which returns an object with an async method "handle" conforming to the ASGI
+# callable's method signature.
 class MyFunction:
-    async def __call__(self, scope, receive, send):
+    async def handle(self, scope, receive, send):
         logging.info("OK")
 
         await send({
@@ -68,7 +70,8 @@ def stop(self):
 
 # Function instance constructor
 # expected to be named exactly "new"
-# Must return a callable which conforms to the ASGI spec.
+# Must return a object which exposes a method "handle" which conforms to the
+# ASGI callable spec.
 def new():
     """ new is the factory function (or constructor) which will create
     a new function instance when invoked.  This must be named "new", and the

src/func_python/http.py

@@ -11,6 +11,7 @@
 
 logging.basicConfig(level=DEFAULT_LOG_LEVEL)
 
+
 def serve(f):
     """serve a function f by wrapping it in an ASGI web application
     and starting.  The function can be either a constructor for a functon
@@ -28,7 +29,7 @@ def serve(f):
             raise
     else:
         raise ValueError("function must be either be a constructor 'new' or a "
-                         "handler 'handle'.")
+                         "handler function 'handle'.")
 
 
 class DefaultFunction:
@@ -38,7 +39,7 @@ class DefaultFunction:
     def __init__(self, handler):
         self.handle = handler
 
-    async def __call__(self, scope, receive, send):
+    async def handle(self, scope, receive, send):
         # delegate to the handler implementation provided during construction.
         await self.handle(scope, receive, send)
 
@@ -47,6 +48,9 @@ class ASGIApplication():
     def __init__(self, f):
         self.f = f
         self.stop_event = asyncio.Event()
+        if hasattr(self.f, "handle") is not True:
+            raise AttributeError( "Function must implement a 'handle' method.")
+
         # Inform the user via logs that defaults will be used for health
         # endpoints if no matchin methods were provided.
         if hasattr(self.f, "alive") is not True:
@@ -125,10 +129,7 @@ async def __call__(self, scope, receive, send):
             elif scope['path'] == '/health/readiness':
                 await self.handle_readiness(scope, receive, send)
             else:
-                if callable(self.f):
-                    await self.f(scope, receive, send)
-                else:
-                    raise Exception("function does not implement handle")
+                await self.f.handle(scope, receive, send)
         except Exception as e:
             await send_exception(send, 500, f"Error: {e}")
 

tests/test_http.py

@@ -10,16 +10,18 @@
 
 # Set a dynamic test URL using an environment variable
 os.environ["LISTEN_ADDRESS"] = os.getenv("LISTEN_ADDRESS", "127.0.0.1:8081")
+
 # Retrieve the LISTEN_ADDRESS for use in the tests
 LISTEN_ADDRESS = os.getenv("LISTEN_ADDRESS")
 
+
 def test_static():
     """
     ensures that a user function developed using the default "static"
     style (method signature) is served by the middleware.
     """
 
-    # Functoin
+    # Function
     # An example minimal "static" user function which will be
     # exposed on the network as an ASGI service by the middleware.
     async def handle(scope, receive, send):
@@ -81,7 +83,7 @@ def test_instanced():
     # An example standard "instanced" function (user's Function) which is
     # exposed on the network as an ASGI service by the middleware.
     class MyFunction:
-        async def __call__(self, scope, receive, send):
+        async def handle(self, scope, receive, send):
             await send({
                 'type': 'http.response.start',
                 'status': 200,