synapse/tests/util/caches/test_descriptors.py

#
# This file is licensed under the Affero General Public License (AGPL) version 3.
#
# Copyright 2016 OpenMarket Ltd
# Copyright (C) 2023 New Vector, Ltd
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# See the GNU Affero General Public License for more details:
# <https://www.gnu.org/licenses/agpl-3.0.html>.
#
# Originally licensed under the Apache License, Version 2.0:
# <http://www.apache.org/licenses/LICENSE-2.0>.
#
# [This file includes modifications made by New Vector Limited]
#
#
import logging
from typing import (
    Any,
    Generator,
    Iterable,
    List,
    Mapping,
    NoReturn,
    Optional,
    Set,
    Tuple,
    cast,
)
from unittest import mock

from twisted.internet import defer, reactor
from twisted.internet.defer import CancelledError, Deferred
from twisted.internet.interfaces import IReactorTime

from synapse.api.errors import SynapseError
from synapse.logging.context import (
    SENTINEL_CONTEXT,
    LoggingContext,
    PreserveLoggingContext,
    current_context,
    make_deferred_yieldable,
)
from synapse.util.caches import descriptors
from synapse.util.caches.descriptors import _CacheContext, cached, cachedList

from tests import unittest
from tests.test_utils import get_awaitable_result

logger = logging.getLogger(__name__)


def run_on_reactor() -> "Deferred[int]":
    d: "Deferred[int]" = Deferred()
    cast(IReactorTime, reactor).callLater(0, d.callback, 0)
    return make_deferred_yieldable(d)


class DescriptorTestCase(unittest.TestCase):
    @defer.inlineCallbacks
    def test_cache(self) -> Generator["Deferred[Any]", object, None]:
        class Cls:
            def __init__(self) -> None:
                self.mock = mock.Mock()

            @descriptors.cached()
            def fn(self, arg1: int, arg2: int) -> str:
                return self.mock(arg1, arg2)

        obj = Cls()

        obj.mock.return_value = "fish"
        r = yield obj.fn(1, 2)
        self.assertEqual(r, "fish")
        obj.mock.assert_called_once_with(1, 2)
        obj.mock.reset_mock()

        # a call with different params should call the mock again
        obj.mock.return_value = "chips"
        r = yield obj.fn(1, 3)
        self.assertEqual(r, "chips")
        obj.mock.assert_called_once_with(1, 3)
        obj.mock.reset_mock()

        # the two values should now be cached
        r = yield obj.fn(1, 2)
        self.assertEqual(r, "fish")
        r = yield obj.fn(1, 3)
        self.assertEqual(r, "chips")
        obj.mock.assert_not_called()

    @defer.inlineCallbacks
    def test_cache_num_args(self) -> Generator["Deferred[Any]", object, None]:
        """Only the first num_args arguments should matter to the cache"""

        class Cls:
            def __init__(self) -> None:
                self.mock = mock.Mock()

            @descriptors.cached(num_args=1)
            def fn(self, arg1: int, arg2: int) -> str:
                return self.mock(arg1, arg2)

        obj = Cls()
        obj.mock.return_value = "fish"
        r = yield obj.fn(1, 2)
        self.assertEqual(r, "fish")
        obj.mock.assert_called_once_with(1, 2)
        obj.mock.reset_mock()

        # a call with different params should call the mock again
        obj.mock.return_value = "chips"
        r = yield obj.fn(2, 3)
        self.assertEqual(r, "chips")
        obj.mock.assert_called_once_with(2, 3)
        obj.mock.reset_mock()

        # the two values should now be cached; we should be able to vary
        # the second argument and still get the cached result.
        r = yield obj.fn(1, 4)
        self.assertEqual(r, "fish")
        r = yield obj.fn(2, 5)
        self.assertEqual(r, "chips")
        obj.mock.assert_not_called()

    @defer.inlineCallbacks
    def test_cache_uncached_args(self) -> Generator["Deferred[Any]", object, None]:
        """
        Only the arguments not named in uncached_args should matter to the cache

        Note that this is identical to test_cache_num_args, but provides the
        arguments differently.
        """

        class Cls:
            # Note that it is important that this is not the last argument to
            # test behaviour of skipping arguments properly.
            @descriptors.cached(uncached_args=("arg2",))
            def fn(self, arg1: int, arg2: int, arg3: int) -> str:
                return self.mock(arg1, arg2, arg3)

            def __init__(self) -> None:
                self.mock = mock.Mock()

        obj = Cls()
        obj.mock.return_value = "fish"
        r = yield obj.fn(1, 2, 3)
        self.assertEqual(r, "fish")
        obj.mock.assert_called_once_with(1, 2, 3)
        obj.mock.reset_mock()

        # a call with different params should call the mock again
        obj.mock.return_value = "chips"
        r = yield obj.fn(2, 3, 4)
        self.assertEqual(r, "chips")
        obj.mock.assert_called_once_with(2, 3, 4)
        obj.mock.reset_mock()

        # the two values should now be cached; we should be able to vary
        # the second argument and still get the cached result.
        r = yield obj.fn(1, 4, 3)
        self.assertEqual(r, "fish")
        r = yield obj.fn(2, 5, 4)
        self.assertEqual(r, "chips")
        obj.mock.assert_not_called()

    @defer.inlineCallbacks
    def test_cache_kwargs(self) -> Generator["Deferred[Any]", object, None]:
        """Test that keyword arguments are treated properly"""

        class Cls:
            def __init__(self) -> None:
                self.mock = mock.Mock()

            @descriptors.cached()
            def fn(self, arg1: int, kwarg1: int = 2) -> str:
                return self.mock(arg1, kwarg1=kwarg1)

        obj = Cls()
        obj.mock.return_value = "fish"
        r = yield obj.fn(1, kwarg1=2)
        self.assertEqual(r, "fish")
        obj.mock.assert_called_once_with(1, kwarg1=2)
        obj.mock.reset_mock()

        # a call with different params should call the mock again
        obj.mock.return_value = "chips"
        r = yield obj.fn(1, kwarg1=3)
        self.assertEqual(r, "chips")
        obj.mock.assert_called_once_with(1, kwarg1=3)
        obj.mock.reset_mock()

        # the values should now be cached.
        r = yield obj.fn(1, kwarg1=2)
        self.assertEqual(r, "fish")
        # We should be able to not provide kwarg1 and get the cached value back.
        r = yield obj.fn(1)
        self.assertEqual(r, "fish")
        # Keyword arguments can be in any order.
        r = yield obj.fn(kwarg1=2, arg1=1)
        self.assertEqual(r, "fish")
        obj.mock.assert_not_called()

    def test_cache_with_sync_exception(self) -> None:
        """If the wrapped function throws synchronously, things should continue to work"""

        class Cls:
            @cached()
            def fn(self, arg1: int) -> NoReturn:
                raise SynapseError(100, "mai spoon iz too big!!1")

        obj = Cls()

        # this should fail immediately
        d = obj.fn(1)
        self.failureResultOf(d, SynapseError)

        # ... leaving the cache empty
        self.assertEqual(len(obj.fn.cache.cache), 0)

        # and a second call should result in a second exception
        d = obj.fn(1)
        self.failureResultOf(d, SynapseError)

    def test_cache_with_async_exception(self) -> None:
        """The wrapped function returns a failure"""

        class Cls:
            result: Optional[Deferred] = None
            call_count = 0

            @cached()
            def fn(self, arg1: int) -> Deferred:
                self.call_count += 1
                assert self.result is not None
                return self.result

        obj = Cls()
        callbacks: Set[str] = set()

        # set off an asynchronous request
        origin_d: Deferred = Deferred()
        obj.result = origin_d

        d1 = obj.fn(1, on_invalidate=lambda: callbacks.add("d1"))
        self.assertFalse(d1.called)

        # a second request should also return a deferred, but should not call the
        # function itself.
        d2 = obj.fn(1, on_invalidate=lambda: callbacks.add("d2"))
        self.assertFalse(d2.called)
        self.assertEqual(obj.call_count, 1)

        # no callbacks yet
        self.assertEqual(callbacks, set())

        # the original request fails
        e = Exception("bzz")
        origin_d.errback(e)

        # ... which should cause the lookups to fail similarly
        self.assertIs(self.failureResultOf(d1, Exception).value, e)
        self.assertIs(self.failureResultOf(d2, Exception).value, e)

        # ... and the callbacks to have been, uh, called.
        self.assertEqual(callbacks, {"d1", "d2"})

        # ... leaving the cache empty
        self.assertEqual(len(obj.fn.cache.cache), 0)

        # and a second call should work as normal
        obj.result = defer.succeed(100)
        d3 = obj.fn(1)
        self.assertEqual(self.successResultOf(d3), 100)
        self.assertEqual(obj.call_count, 2)

    def test_cache_logcontexts(self) -> Deferred:
        """Check that logcontexts are set and restored correctly when
        using the cache."""

        complete_lookup: Deferred = Deferred()

        class Cls:
            @descriptors.cached()
            def fn(self, arg1: int) -> "Deferred[int]":
                @defer.inlineCallbacks
                def inner_fn() -> Generator["Deferred[object]", object, int]:
                    with PreserveLoggingContext():
                        yield complete_lookup
                    return 1

                return inner_fn()

        @defer.inlineCallbacks
        def do_lookup() -> Generator["Deferred[Any]", object, int]:
            with LoggingContext("c1") as c1:
                r = yield obj.fn(1)
                self.assertEqual(current_context(), c1)
            return cast(int, r)

        def check_result(r: int) -> None:
            self.assertEqual(r, 1)

        obj = Cls()

        # set off a deferred which will do a cache lookup
        d1 = do_lookup()
        self.assertEqual(current_context(), SENTINEL_CONTEXT)
        d1.addCallback(check_result)

        # and another
        d2 = do_lookup()
        self.assertEqual(current_context(), SENTINEL_CONTEXT)
        d2.addCallback(check_result)

        # let the lookup complete
        complete_lookup.callback(None)

        return defer.gatherResults([d1, d2])

    def test_cache_logcontexts_with_exception(self) -> "Deferred[None]":
        """Check that the cache sets and restores logcontexts correctly when
        the lookup function throws an exception"""

        class Cls:
            @descriptors.cached()
            def fn(self, arg1: int) -> Deferred:
                @defer.inlineCallbacks
                def inner_fn() -> Generator["Deferred[Any]", object, NoReturn]:
                    # we want this to behave like an asynchronous function
                    yield run_on_reactor()
                    raise SynapseError(400, "blah")

                return inner_fn()

        @defer.inlineCallbacks
        def do_lookup() -> Generator["Deferred[object]", object, None]:
            with LoggingContext("c1") as c1:
                try:
                    d = obj.fn(1)
                    self.assertEqual(
                        current_context(),
                        SENTINEL_CONTEXT,
                    )
                    yield d
                    self.fail("No exception thrown")
                except SynapseError:
                    pass

                self.assertEqual(current_context(), c1)

            # the cache should now be empty
            self.assertEqual(len(obj.fn.cache.cache), 0)

        obj = Cls()

        # set off a deferred which will do a cache lookup
        d1 = do_lookup()
        self.assertEqual(current_context(), SENTINEL_CONTEXT)

        return d1

    @defer.inlineCallbacks
    def test_cache_default_args(self) -> Generator["Deferred[Any]", object, None]:
        class Cls:
            def __init__(self) -> None:
                self.mock = mock.Mock()

            @descriptors.cached()
            def fn(self, arg1: int, arg2: int = 2, arg3: int = 3) -> str:
                return self.mock(arg1, arg2, arg3)

        obj = Cls()

        obj.mock.return_value = "fish"
        r = yield obj.fn(1, 2, 3)
        self.assertEqual(r, "fish")
        obj.mock.assert_called_once_with(1, 2, 3)
        obj.mock.reset_mock()

        # a call with same params shouldn't call the mock again
        r = yield obj.fn(1, 2)
        self.assertEqual(r, "fish")
        obj.mock.assert_not_called()
        obj.mock.reset_mock()

        # a call with different params should call the mock again
        obj.mock.return_value = "chips"
        r = yield obj.fn(2, 3)
        self.assertEqual(r, "chips")
        obj.mock.assert_called_once_with(2, 3, 3)
        obj.mock.reset_mock()

        # the two values should now be cached
        r = yield obj.fn(1, 2)
        self.assertEqual(r, "fish")
        r = yield obj.fn(2, 3)
        self.assertEqual(r, "chips")
        obj.mock.assert_not_called()

    def test_cache_iterable(self) -> None:
        class Cls:
            def __init__(self) -> None:
                self.mock = mock.Mock()

            @descriptors.cached(iterable=True)
            def fn(self, arg1: int, arg2: int) -> Tuple[str, ...]:
                return self.mock(arg1, arg2)

        obj = Cls()

        obj.mock.return_value = ("spam", "eggs")
        r = obj.fn(1, 2)
        self.assertEqual(r.result, ("spam", "eggs"))
        obj.mock.assert_called_once_with(1, 2)
        obj.mock.reset_mock()

        # a call with different params should call the mock again
        obj.mock.return_value = ("chips",)
        r = obj.fn(1, 3)
        self.assertEqual(r.result, ("chips",))
        obj.mock.assert_called_once_with(1, 3)
        obj.mock.reset_mock()

        # the two values should now be cached
        self.assertEqual(len(obj.fn.cache.cache), 3)

        r = obj.fn(1, 2)
        self.assertEqual(r.result, ("spam", "eggs"))
        r = obj.fn(1, 3)
        self.assertEqual(r.result, ("chips",))
        obj.mock.assert_not_called()

    def test_cache_iterable_with_sync_exception(self) -> None:
        """If the wrapped function throws synchronously, things should continue to work"""

        class Cls:
            @descriptors.cached(iterable=True)
            def fn(self, arg1: int) -> NoReturn:
                raise SynapseError(100, "mai spoon iz too big!!1")

        obj = Cls()

        # this should fail immediately
        d = obj.fn(1)
        self.failureResultOf(d, SynapseError)

        # ... leaving the cache empty
        self.assertEqual(len(obj.fn.cache.cache), 0)

        # and a second call should result in a second exception
        d = obj.fn(1)
        self.failureResultOf(d, SynapseError)

    def test_invalidate_cascade(self) -> None:
        """Invalidations should cascade up through cache contexts"""

        class Cls:
            @cached(cache_context=True)
            async def func1(self, key: str, cache_context: _CacheContext) -> int:
                return await self.func2(key, on_invalidate=cache_context.invalidate)

            @cached(cache_context=True)
            async def func2(self, key: str, cache_context: _CacheContext) -> int:
                return await self.func3(key, on_invalidate=cache_context.invalidate)

            @cached(cache_context=True)
            async def func3(self, key: str, cache_context: _CacheContext) -> int:
                self.invalidate = cache_context.invalidate
                return 42

        obj = Cls()

        top_invalidate = mock.Mock()
        r = get_awaitable_result(obj.func1("k1", on_invalidate=top_invalidate))
        self.assertEqual(r, 42)
        obj.invalidate()
        top_invalidate.assert_called_once()

    def test_cancel(self) -> None:
        """Test that cancelling a lookup does not cancel other lookups"""
        complete_lookup: "Deferred[None]" = Deferred()

        class Cls:
            @cached()
            async def fn(self, arg1: int) -> str:
                await complete_lookup
                return str(arg1)

        obj = Cls()

        d1 = obj.fn(123)
        d2 = obj.fn(123)
        self.assertFalse(d1.called)
        self.assertFalse(d2.called)

        # Cancel `d1`, which is the lookup that caused `fn` to run.
        d1.cancel()

        # `d2` should complete normally.
        complete_lookup.callback(None)
        self.failureResultOf(d1, CancelledError)
        self.assertEqual(d2.result, "123")

    def test_cancel_logcontexts(self) -> None:
        """Test that cancellation does not break logcontexts.

        * The `CancelledError` must be raised with the correct logcontext.
        * The inner lookup must not resume with a finished logcontext.
        * The inner lookup must not restore a finished logcontext when done.
        """
        complete_lookup: "Deferred[None]" = Deferred()

        class Cls:
            inner_context_was_finished = False

            @cached()
            async def fn(self, arg1: int) -> str:
                await make_deferred_yieldable(complete_lookup)
                self.inner_context_was_finished = current_context().finished
                return str(arg1)

        obj = Cls()

        async def do_lookup() -> None:
            with LoggingContext("c1") as c1:
                try:
                    await obj.fn(123)
                    self.fail("No CancelledError thrown")
                except CancelledError:
                    self.assertEqual(
                        current_context(),
                        c1,
                        "CancelledError was not raised with the correct logcontext",
                    )
                    # suppress the error and succeed

        d = defer.ensureDeferred(do_lookup())
        d.cancel()

        complete_lookup.callback(None)
        self.successResultOf(d)
        self.assertFalse(
            obj.inner_context_was_finished, "Tried to restart a finished logcontext"
        )
        self.assertEqual(current_context(), SENTINEL_CONTEXT)


class CacheDecoratorTestCase(unittest.HomeserverTestCase):
    """More tests for @cached

    The following is a set of tests that got lost in a different file for a while.

    There are probably duplicates of the tests in DescriptorTestCase. Ideally the
    duplicates would be removed and the two sets of classes combined.
    """

    @defer.inlineCallbacks
    def test_passthrough(self) -> Generator["Deferred[Any]", object, None]:
        class A:
            @cached()
            def func(self, key: str) -> str:
                return key

        a = A()

        self.assertEqual((yield a.func("foo")), "foo")
        self.assertEqual((yield a.func("bar")), "bar")

    @defer.inlineCallbacks
    def test_hit(self) -> Generator["Deferred[Any]", object, None]:
        callcount = [0]

        class A:
            @cached()
            def func(self, key: str) -> str:
                callcount[0] += 1
                return key

        a = A()
        yield a.func("foo")

        self.assertEqual(callcount[0], 1)

        self.assertEqual((yield a.func("foo")), "foo")
        self.assertEqual(callcount[0], 1)

    @defer.inlineCallbacks
    def test_invalidate(self) -> Generator["Deferred[Any]", object, None]:
        callcount = [0]

        class A:
            @cached()
            def func(self, key: str) -> str:
                callcount[0] += 1
                return key

        a = A()
        yield a.func("foo")

        self.assertEqual(callcount[0], 1)

        a.func.invalidate(("foo",))

        yield a.func("foo")

        self.assertEqual(callcount[0], 2)

    def test_invalidate_missing(self) -> None:
        class A:
            @cached()
            def func(self, key: str) -> str:
                return key

        A().func.invalidate(("what",))

    @defer.inlineCallbacks
    def test_max_entries(self) -> Generator["Deferred[Any]", object, None]:
        callcount = [0]

        class A:
            @cached(max_entries=10)
            def func(self, key: int) -> int:
                callcount[0] += 1
                return key

        a = A()

        for k in range(12):
            yield a.func(k)

        self.assertEqual(callcount[0], 12)

        # There must have been at least 2 evictions, meaning if we calculate
        # all 12 values again, we must get called at least 2 more times
        for k in range(12):
            yield a.func(k)

        self.assertTrue(
            callcount[0] >= 14, msg="Expected callcount >= 14, got %d" % (callcount[0])
        )

    def test_prefill(self) -> None:
        callcount = [0]

        d = defer.succeed(123)

        class A:
            @cached()
            def func(self, key: str) -> "Deferred[int]":
                callcount[0] += 1
                return d

        a = A()

        a.func.prefill(("foo",), 456)

        self.assertEqual(a.func("foo").result, 456)
        self.assertEqual(callcount[0], 0)

    @defer.inlineCallbacks
    def test_invalidate_context(self) -> Generator["Deferred[Any]", object, None]:
        callcount = [0]
        callcount2 = [0]

        class A:
            @cached()
            def func(self, key: str) -> str:
                callcount[0] += 1
                return key

            @cached(cache_context=True)
            def func2(self, key: str, cache_context: _CacheContext) -> "Deferred[str]":
                callcount2[0] += 1
                return self.func(key, on_invalidate=cache_context.invalidate)

        a = A()
        yield a.func2("foo")

        self.assertEqual(callcount[0], 1)
        self.assertEqual(callcount2[0], 1)

        a.func.invalidate(("foo",))
        yield a.func("foo")

        self.assertEqual(callcount[0], 2)
        self.assertEqual(callcount2[0], 1)

        yield a.func2("foo")

        self.assertEqual(callcount[0], 2)
        self.assertEqual(callcount2[0], 2)

    @defer.inlineCallbacks
    def test_eviction_context(self) -> Generator["Deferred[Any]", object, None]:
        callcount = [0]
        callcount2 = [0]

        class A:
            @cached(max_entries=2)
            def func(self, key: str) -> str:
                callcount[0] += 1
                return key

            @cached(cache_context=True)
            def func2(self, key: str, cache_context: _CacheContext) -> "Deferred[str]":
                callcount2[0] += 1
                return self.func(key, on_invalidate=cache_context.invalidate)

        a = A()
        yield a.func2("foo")
        yield a.func2("foo2")

        self.assertEqual(callcount[0], 2)
        self.assertEqual(callcount2[0], 2)

        yield a.func2("foo")
        self.assertEqual(callcount[0], 2)
        self.assertEqual(callcount2[0], 2)

        yield a.func("foo3")

        self.assertEqual(callcount[0], 3)
        self.assertEqual(callcount2[0], 2)

        yield a.func2("foo")

        self.assertEqual(callcount[0], 4)
        self.assertEqual(callcount2[0], 3)

    @defer.inlineCallbacks
    def test_double_get(self) -> Generator["Deferred[Any]", object, None]:
        callcount = [0]
        callcount2 = [0]

        class A:
            @cached()
            def func(self, key: str) -> str:
                callcount[0] += 1
                return key

            @cached(cache_context=True)
            def func2(self, key: str, cache_context: _CacheContext) -> "Deferred[str]":
                callcount2[0] += 1
                return self.func(key, on_invalidate=cache_context.invalidate)

        a = A()
        a.func2.cache.cache = mock.Mock(wraps=a.func2.cache.cache)

        yield a.func2("foo")

        self.assertEqual(callcount[0], 1)
        self.assertEqual(callcount2[0], 1)

        a.func2.invalidate(("foo",))
        self.assertEqual(a.func2.cache.cache.del_multi.call_count, 1)

        yield a.func2("foo")
        a.func2.invalidate(("foo",))
        self.assertEqual(a.func2.cache.cache.del_multi.call_count, 2)

        self.assertEqual(callcount[0], 1)
        self.assertEqual(callcount2[0], 2)

        a.func.invalidate(("foo",))
        self.assertEqual(a.func2.cache.cache.del_multi.call_count, 3)
        yield a.func("foo")

        self.assertEqual(callcount[0], 2)
        self.assertEqual(callcount2[0], 2)

        yield a.func2("foo")

        self.assertEqual(callcount[0], 2)
        self.assertEqual(callcount2[0], 3)


class CachedListDescriptorTestCase(unittest.TestCase):
    @defer.inlineCallbacks
    def test_cache(self) -> Generator["Deferred[Any]", object, None]:
        class Cls:
            def __init__(self) -> None:
                self.mock = mock.Mock()

            @descriptors.cached()
            def fn(self, arg1: int, arg2: int) -> None:
                pass

            @descriptors.cachedList(cached_method_name="fn", list_name="args1")
            async def list_fn(
                self, args1: Iterable[int], arg2: int
            ) -> Mapping[int, str]:
                context = current_context()
                assert isinstance(context, LoggingContext)
                assert context.name == "c1"
                # we want this to behave like an asynchronous function
                await run_on_reactor()
                context = current_context()
                assert isinstance(context, LoggingContext)
                assert context.name == "c1"
                return self.mock(args1, arg2)

        with LoggingContext("c1") as c1:
            obj = Cls()
            obj.mock.return_value = {10: "fish", 20: "chips"}

            # start the lookup off
            d1 = obj.list_fn([10, 20], 2)
            self.assertEqual(current_context(), SENTINEL_CONTEXT)
            r = yield d1
            self.assertEqual(current_context(), c1)
            obj.mock.assert_called_once_with({10, 20}, 2)
            self.assertEqual(r, {10: "fish", 20: "chips"})
            obj.mock.reset_mock()

            # a call with different params should call the mock again
            obj.mock.return_value = {30: "peas"}
            r = yield obj.list_fn([20, 30], 2)
            obj.mock.assert_called_once_with({30}, 2)
            self.assertEqual(r, {20: "chips", 30: "peas"})
            obj.mock.reset_mock()

            # all the values should now be cached
            r = yield obj.fn(10, 2)
            self.assertEqual(r, "fish")
            r = yield obj.fn(20, 2)
            self.assertEqual(r, "chips")
            r = yield obj.fn(30, 2)
            self.assertEqual(r, "peas")
            r = yield obj.list_fn([10, 20, 30], 2)
            obj.mock.assert_not_called()
            self.assertEqual(r, {10: "fish", 20: "chips", 30: "peas"})

            # we should also be able to use a (single-use) iterable, and should
            # deduplicate the keys
            obj.mock.reset_mock()
            obj.mock.return_value = {40: "gravy"}
            iterable = (x for x in [10, 40, 40])
            r = yield obj.list_fn(iterable, 2)
            obj.mock.assert_called_once_with({40}, 2)
            self.assertEqual(r, {10: "fish", 40: "gravy"})

    def test_concurrent_lookups(self) -> None:
        """All concurrent lookups should get the same result"""

        class Cls:
            def __init__(self) -> None:
                self.mock = mock.Mock()

            @descriptors.cached()
            def fn(self, arg1: int) -> None:
                pass

            @descriptors.cachedList(cached_method_name="fn", list_name="args1")
            def list_fn(self, args1: List[int]) -> "Deferred[Mapping[int, str]]":
                return self.mock(args1)

        obj = Cls()
        deferred_result: "Deferred[Mapping[int, str]]" = Deferred()
        obj.mock.return_value = deferred_result

        # start off several concurrent lookups of the same key
        d1 = obj.list_fn([10])
        d2 = obj.list_fn([10])
        d3 = obj.list_fn([10])

        # the mock should have been called exactly once
        obj.mock.assert_called_once_with({10})
        obj.mock.reset_mock()

        # ... and none of the calls should yet be complete
        self.assertFalse(d1.called)
        self.assertFalse(d2.called)
        self.assertFalse(d3.called)

        # complete the lookup. @cachedList functions need to complete with a map
        # of input->result
        deferred_result.callback({10: "peas"})

        # ... which should give the right result to all the callers
        self.assertEqual(self.successResultOf(d1), {10: "peas"})
        self.assertEqual(self.successResultOf(d2), {10: "peas"})
        self.assertEqual(self.successResultOf(d3), {10: "peas"})

    @defer.inlineCallbacks
    def test_invalidate(self) -> Generator["Deferred[Any]", object, None]:
        """Make sure that invalidation callbacks are called."""

        class Cls:
            def __init__(self) -> None:
                self.mock = mock.Mock()

            @descriptors.cached()
            def fn(self, arg1: int, arg2: int) -> None:
                pass

            @descriptors.cachedList(cached_method_name="fn", list_name="args1")
            async def list_fn(self, args1: List[int], arg2: int) -> Mapping[int, str]:
                # we want this to behave like an asynchronous function
                await run_on_reactor()
                return self.mock(args1, arg2)

        obj = Cls()
        invalidate0 = mock.Mock()
        invalidate1 = mock.Mock()

        # cache miss
        obj.mock.return_value = {10: "fish", 20: "chips"}
        r1 = yield obj.list_fn([10, 20], 2, on_invalidate=invalidate0)
        obj.mock.assert_called_once_with({10, 20}, 2)
        self.assertEqual(r1, {10: "fish", 20: "chips"})
        obj.mock.reset_mock()

        # cache hit
        r2 = yield obj.list_fn([10, 20], 2, on_invalidate=invalidate1)
        obj.mock.assert_not_called()
        self.assertEqual(r2, {10: "fish", 20: "chips"})

        invalidate0.assert_not_called()
        invalidate1.assert_not_called()

        # now if we invalidate the keys, both invalidations should get called
        obj.fn.invalidate((10, 2))
        invalidate0.assert_called_once()
        invalidate1.assert_called_once()

    def test_cancel(self) -> None:
        """Test that cancelling a lookup does not cancel other lookups"""
        complete_lookup: "Deferred[None]" = Deferred()

        class Cls:
            @cached()
            def fn(self, arg1: int) -> None:
                pass

            @cachedList(cached_method_name="fn", list_name="args")
            async def list_fn(self, args: List[int]) -> Mapping[int, str]:
                await complete_lookup
                return {arg: str(arg) for arg in args}

        obj = Cls()

        d1 = obj.list_fn([123, 456])
        d2 = obj.list_fn([123, 456, 789])
        self.assertFalse(d1.called)
        self.assertFalse(d2.called)

        d1.cancel()

        # `d2` should complete normally.
        complete_lookup.callback(None)
        self.failureResultOf(d1, CancelledError)
        self.assertEqual(d2.result, {123: "123", 456: "456", 789: "789"})

    def test_cancel_logcontexts(self) -> None:
        """Test that cancellation does not break logcontexts.

        * The `CancelledError` must be raised with the correct logcontext.
        * The inner lookup must not resume with a finished logcontext.
        * The inner lookup must not restore a finished logcontext when done.
        """
        complete_lookup: "Deferred[None]" = Deferred()

        class Cls:
            inner_context_was_finished = False

            @cached()
            def fn(self, arg1: int) -> None:
                pass

            @cachedList(cached_method_name="fn", list_name="args")
            async def list_fn(self, args: List[int]) -> Mapping[int, str]:
                await make_deferred_yieldable(complete_lookup)
                self.inner_context_was_finished = current_context().finished
                return {arg: str(arg) for arg in args}

        obj = Cls()

        async def do_lookup() -> None:
            with LoggingContext("c1") as c1:
                try:
                    await obj.list_fn([123])
                    self.fail("No CancelledError thrown")
                except CancelledError:
                    self.assertEqual(
                        current_context(),
                        c1,
                        "CancelledError was not raised with the correct logcontext",
                    )
                    # suppress the error and succeed

        d = defer.ensureDeferred(do_lookup())
        d.cancel()

        complete_lookup.callback(None)
        self.successResultOf(d)
        self.assertFalse(
            obj.inner_context_was_finished, "Tried to restart a finished logcontext"
        )
        self.assertEqual(current_context(), SENTINEL_CONTEXT)

    def test_num_args_mismatch(self) -> None:
        """
        Make sure someone does not accidentally use @cachedList on a method with
        a mismatch in the number args to the underlying single cache method.
        """

        class Cls:
            @descriptors.cached(tree=True)
            def fn(self, room_id: str, event_id: str) -> None:
                pass

            # This is wrong ❌. `@cachedList` expects to be given the same number
            # of arguments as the underlying cached function, just with one of
            # the arguments being an iterable
            @descriptors.cachedList(cached_method_name="fn", list_name="keys")
            def list_fn(self, keys: Iterable[Tuple[str, str]]) -> None:
                pass

            # Corrected syntax ✅
            #
            # @cachedList(cached_method_name="fn", list_name="event_ids")
            # async def list_fn(
            #     self, room_id: str, event_ids: Collection[str],
            # )

        obj = Cls()

        # Make sure this raises an error about the arg mismatch
        with self.assertRaises(TypeError):
            obj.list_fn([("foo", "bar")])