feat: check that async_early_return is applied on async functions (#79)

* feat: check that async_early_return is applied on async functions

* chore: ignore lint error

* chore: reorder checks

meiga/decorators/async_decoration_error.py

@@ -0,0 +1,6 @@
+from meiga.error import Error
+
+
+class AsyncDecorationError(Error):
+    def __init__(self) -> None:
+        self.message = "meiga async decorators must be declared on async functions"

meiga/decorators/async_early_return.py

@@ -1,7 +1,10 @@
+import inspect
 import sys
 from functools import wraps
 from typing import Any, Callable, Coroutine, TypeVar, cast
 
+from meiga.decorators.async_decoration_error import AsyncDecorationError
+
 if sys.version_info < (3, 10):  # pragma: no cover
     from typing_extensions import ParamSpec
 else:
@@ -29,6 +32,8 @@ async def _async_early_return(*args: P.args, **kwargs: P.kwargs) -> R:
                 return Failure(UnexpectedDecorationOrderError())  # type: ignore
             elif isinstance(func, classmethod):
                 return Failure(UnexpectedDecorationOrderError())  # type: ignore
+            elif not inspect.iscoroutinefunction(func):
+                return Failure(AsyncDecorationError())  # type: ignore
             else:
                 return await func(*args, **kwargs)
         except WaitingForEarlyReturn as exc:

meiga/handlers.py

@@ -27,7 +27,9 @@ def execute(self, result: Result[TS, TF]) -> None:
                 self.func(result.value)
 
 
-class OnSuccessHandler(Handler): ...
+class OnSuccessHandler(Handler):
+    ...
 
 
-class OnFailureHandler(Handler): ...
+class OnFailureHandler(Handler):
+    ...

tests/unit/doc/example_with_meiga.py

@@ -3,10 +3,12 @@
 from meiga import Error, Failure, Result, Success
 
 
-class NoSuchKey(Error): ...
+class NoSuchKey(Error):
+    ...
 
 
-class TypeMismatch(Error): ...
+class TypeMismatch(Error):
+    ...
 
 
 def string_from_key(dictionary: dict, key: str) -> Result[str, NoSuchKey | TypeMismatch]:

tests/unit/doc/example_without_meiga.py

@@ -1,7 +1,9 @@
-class NoSuchKey(Exception): ...
+class NoSuchKey(Exception):
+    ...
 
 
-class TypeMismatch(Exception): ...
+class TypeMismatch(Exception):
+    ...
 
 
 # This return value masks the behavior of the unhappy path (Exceptions). 🥲

tests/unit/test_async_early_return.py

@@ -3,6 +3,7 @@
 from meiga import BoolResult, Error, async_early_return, isFailure, isSuccess
 from meiga.assertions import assert_failure, assert_success
 from meiga.decorators import UnexpectedDecorationOrderError
+from meiga.decorators.async_decoration_error import AsyncDecorationError
 
 
 @pytest.mark.unit
@@ -107,3 +108,15 @@ async def decorated_method(cls) -> BoolResult:
         result = await MyClass.decorated_method()
         assert_failure(result, value_is_instance_of=UnexpectedDecorationOrderError)
         assert result.value.message == "meiga decorators must be declared after a @staticmethod, @classmethod"
+
+    async def should_return_an_async_decorator_failure_result_with_async_early_return_on_normal_function(
+        self,
+    ):
+        class MyClass:
+            @async_early_return
+            def decorated_method(cls) -> BoolResult:
+                return isSuccess
+
+        result = await MyClass.decorated_method()
+        assert_failure(result, value_is_instance_of=AsyncDecorationError)
+        assert result.value.message == "meiga async decorators must be declared on async functions"