Type hinting for lru_cache on methods (#105)

* added unittest to verify lru_cache works on methods

* added type tests

* added stub for lrucache

* preserve cache on type lookup

* documented type testing scheme

* ignore type tests for coverage and pytest

Author: maxfischer2781

.codecov.yml

@@ -0,0 +1,3 @@
+ignore:
+  # type tests are not execute, so there is no code coverage
+  - "typetests"

asyncstdlib/_lrucache.pyi

@@ -0,0 +1,61 @@
+from ._typing import AC, Protocol, R as R, TypedDict
+from typing import (
+    Any,
+    Awaitable,
+    Callable,
+    NamedTuple,
+    Optional,
+    overload,
+)
+
+class CacheInfo(NamedTuple):
+    hits: int
+    misses: int
+    maxsize: Optional[int]
+    currsize: int
+
+class CacheParameters(TypedDict):
+    maxsize: Optional[int]
+    typed: bool
+
+class LRUAsyncCallable(Protocol[AC]):
+    __call__: AC
+    @overload
+    def __get__(
+        self: LRUAsyncCallable[AC],
+        instance: None,
+        owner: Optional[type] = ...,
+    ) -> LRUAsyncCallable[AC]: ...
+    @overload
+    def __get__(
+        self: LRUAsyncCallable[Callable[..., Awaitable[R]]],
+        instance: object,
+        owner: Optional[type] = ...,
+    ) -> LRUAsyncBoundCallable[Callable[..., Awaitable[R]]]: ...
+    @property
+    def __wrapped__(self) -> AC: ...
+    def cache_parameters(self) -> CacheParameters: ...
+    def cache_info(self) -> CacheInfo: ...
+    def cache_clear(self) -> None: ...
+    def cache_discard(self, *args: Any, **kwargs: Any) -> None: ...
+
+class LRUAsyncBoundCallable(LRUAsyncCallable[AC]):
+    __self__: object
+    __call__: AC
+    def __get__(
+        self: LRUAsyncBoundCallable[AC],
+        instance: Any,
+        owner: Optional[type] = ...,
+    ) -> LRUAsyncBoundCallable[AC]: ...
+    def __init__(self, lru: LRUAsyncCallable[AC], __self__: object) -> None: ...
+    @property
+    def __wrapped__(self) -> AC: ...
+    @property
+    def __func__(self) -> LRUAsyncCallable[AC]: ...
+
+@overload
+def lru_cache(maxsize: AC, typed: bool = ...) -> LRUAsyncCallable[AC]: ...
+@overload
+def lru_cache(
+    maxsize: Optional[int] = ..., typed: bool = ...
+) -> Callable[[AC], LRUAsyncCallable[AC]]: ...

pyproject.toml

@@ -47,7 +47,7 @@ Source = "https://github.com/maxfischer2781/asyncstdlib"
 include = ["unittests"]
 
 [tool.mypy]
-files = ["asyncstdlib/*.py"]
+files = ["asyncstdlib", "typetests"]
 check_untyped_defs = true
 no_implicit_optional = true
 warn_redundant_casts = true
@@ -62,3 +62,8 @@ disallow_untyped_decorators = true
 warn_return_any = true
 no_implicit_reexport = true
 strict_equality = true
+
+[tool.pytest.ini_options]
+testpaths = [
+    "unittests",
+]

typetests/README.rst

@@ -0,0 +1,37 @@
+=================
+MyPy Type Testing
+=================
+
+This suite contains *type* tests for ``asyncstdlib``.
+These tests follow similar conventions to unittests but are checked by MyPy.
+
+Test Files
+==========
+
+Tests MUST be organised into files, with similar tests grouped together.
+Each test file SHOULD be called as per the pattern ``type_<scope>.py``,
+where ``<scope>`` describes what the tests cover;
+for example, ``test_functools.py`` type-tests the ``functools`` package.
+
+An individual test is a function, method or class and SHOULD be named
+with a `test_` or `Test` prefix for functions/methods or classes, respectively.
+A class SHOULD be considered a test if it contains any tests.
+Tests MUST contain statements to be type-checked:
+- plain statements required to be type consistent,
+  such as passing parameters of expected correct type to a function.
+- assertions about types and exhaustiveness,
+  using `typing.assert_type` or `typing.assert_never`.
+- statements required to be type inconsistent with an expected type error,
+  such as passing parameters of wrong type with `# type: ignore[arg-type]`.
+
+Test files MAY contain non-test functions, methods or classes for use inside tests.
+These SHOULD be type-consistent and not require any type assertions or expected errors.
+
+Test Execution
+==============
+
+Tests MUST be checked by MyPy using
+the ``warn_unused_ignores`` configuration or ``--warn-unused-ignores`` command line
+option.
+This is required for negative type consistency checks,
+i.e. using expected type errors such as ``# type: ignore[arg-type]``.

typetests/test_functools.py

@@ -0,0 +1,23 @@
+from asyncstdlib import lru_cache
+
+
+@lru_cache()
+async def lru_function(a: int) -> int:
+    return a
+
+
+async def test_cache_parameters() -> None:
+    await lru_function(12)
+    await lru_function("wrong parameter type")  # type: ignore[arg-type]
+
+
+class TestLRUMethod:
+    """
+    Test that `lru_cache` works on methods
+    """
+    @lru_cache()
+    async def cached(self) -> int:
+        return 1
+
+    async def test_implicit_self(self) -> int:
+        return await self.cached()

unittests/test_functools.py

@@ -203,6 +203,32 @@ async def pingpong(arg):
         assert pingpong.cache_info().hits == (val + 1) * 2
 
 
+@sync
+async def test_lru_cache_method():
+    """
+    Test that the lru_cache can be used on methods
+    """
+
+    class SelfCached:
+        def __init__(self, ident: int):
+            self.ident = ident
+
+        @a.lru_cache()
+        async def pingpong(self, arg):
+            # return identifier of instance to separate cache entries per instance
+            return arg, self.ident
+
+    for iteration in range(4):
+        instance = SelfCached(iteration)
+        for val in range(20):
+            # 1 read initializes, 2 reads hit
+            assert await instance.pingpong(val) == (val, iteration)
+            assert await instance.pingpong(float(val)) == (val, iteration)
+            assert await instance.pingpong(val) == (val, iteration)
+            assert instance.pingpong.cache_info().misses == val + 1 + 20 * iteration
+            assert instance.pingpong.cache_info().hits == (val + 1 + 20 * iteration) * 2
+
+
 @sync
 async def test_lru_cache_bare():
     @a.lru_cache