fix: allow returning none for generic bindings

azure_functions_worker/bindings/generic.py

@@ -34,6 +34,10 @@ def encode(cls, obj: Any, *,
 
     @classmethod
     def decode(cls, data: datumdef.Datum, *, trigger_metadata) -> typing.Any:
+        # Enabling support for Dapr bindings
+        # https://github.com/Azure/azure-functions-python-worker/issues/1316
+        if data is None:
+            return None
         data_type = data.type
 
         if data_type == 'string':

tests/unittests/generic_functions/foobar_nil_data/function.json

@@ -0,0 +1,11 @@
+{
+    "scriptFile": "main.py",
+    "bindings": [
+      {
+        "type": "generic",
+        "name": "input",
+        "direction": "in"
+      }
+    ]
+  }
+

tests/unittests/generic_functions/foobar_nil_data/main.py

@@ -0,0 +1,7 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License.
+import logging
+
+
+def main(input) -> None:
+    logging.info("Hello World")

tests/unittests/test_mock_generic_functions.py

@@ -195,3 +195,28 @@ async def test_mock_generic_implicit_output_exemption(self):
             # For the Durable Functions durableClient case
             self.assertEqual(r.response.result.status,
                              protos.StatusResult.Failure)
+
+    async def test_mock_generic_as_nil_data(self):
+        async with testutils.start_mockhost(
+                script_root=self.generic_funcs_dir) as host:
+
+            await host.init_worker("4.17.1")
+            func_id, r = await host.load_function('foobar_nil_data')
+
+            self.assertEqual(r.response.function_id, func_id)
+            self.assertEqual(r.response.result.status,
+                             protos.StatusResult.Success)
+
+            _, r = await host.invoke_function(
+                'foobar_nil_data', [
+                    protos.ParameterBinding(
+                        name='input',
+                        data=protos.TypedData()
+                    )
+                ]
+            )
+            self.assertEqual(r.response.result.status,
+                             protos.StatusResult.Success)
+            self.assertEqual(
+                r.response.return_value,
+                protos.TypedData())