mypy plugin to check `@cached` return types (#14911)
Co-authored-by: David Robertson <davidr@element.io> Co-authored-by: Patrick Cloke <patrickc@matrix.org> Co-authored-by: Erik Johnston <erik@matrix.org> Assert that the return type of callables wrapped in @cached and @cachedList are cachable (aka immutable).
This commit is contained in:
parent
5725712d47
commit
1026776380
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@ -0,0 +1 @@
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Improve type hints.
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@ -16,13 +16,24 @@
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can crop up, e.g the cache descriptors.
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"""
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from typing import Callable, Optional, Type
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from typing import Callable, Optional, Tuple, Type, Union
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import mypy.types
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from mypy.erasetype import remove_instance_last_known_values
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from mypy.nodes import ARG_NAMED_OPT
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from mypy.plugin import MethodSigContext, Plugin
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from mypy.errorcodes import ErrorCode
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from mypy.nodes import ARG_NAMED_OPT, TempNode, Var
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from mypy.plugin import FunctionSigContext, MethodSigContext, Plugin
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from mypy.typeops import bind_self
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from mypy.types import CallableType, Instance, NoneType, UnionType
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from mypy.types import (
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AnyType,
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CallableType,
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Instance,
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NoneType,
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TupleType,
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TypeAliasType,
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UninhabitedType,
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UnionType,
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)
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class SynapsePlugin(Plugin):
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@ -36,9 +47,37 @@ class SynapsePlugin(Plugin):
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)
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):
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return cached_function_method_signature
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if fullname in (
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"synapse.util.caches.descriptors._CachedFunctionDescriptor.__call__",
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"synapse.util.caches.descriptors._CachedListFunctionDescriptor.__call__",
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):
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return check_is_cacheable_wrapper
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return None
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def _get_true_return_type(signature: CallableType) -> mypy.types.Type:
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"""
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Get the "final" return type of a callable which might return an Awaitable/Deferred.
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"""
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if isinstance(signature.ret_type, Instance):
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# If a coroutine, unwrap the coroutine's return type.
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if signature.ret_type.type.fullname == "typing.Coroutine":
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return signature.ret_type.args[2]
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# If an awaitable, unwrap the awaitable's final value.
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elif signature.ret_type.type.fullname == "typing.Awaitable":
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return signature.ret_type.args[0]
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# If a Deferred, unwrap the Deferred's final value.
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elif signature.ret_type.type.fullname == "twisted.internet.defer.Deferred":
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return signature.ret_type.args[0]
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# Otherwise, return the raw value of the function.
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return signature.ret_type
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def cached_function_method_signature(ctx: MethodSigContext) -> CallableType:
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"""Fixes the `CachedFunction.__call__` signature to be correct.
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@ -47,16 +86,17 @@ def cached_function_method_signature(ctx: MethodSigContext) -> CallableType:
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1. the `self` argument needs to be marked as "bound";
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2. any `cache_context` argument should be removed;
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3. an optional keyword argument `on_invalidated` should be added.
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4. Wrap the return type to always be a Deferred.
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"""
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# First we mark this as a bound function signature.
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signature = bind_self(ctx.default_signature)
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# 1. Mark this as a bound function signature.
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signature: CallableType = bind_self(ctx.default_signature)
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# Secondly, we remove any "cache_context" args.
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# 2. Remove any "cache_context" args.
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#
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# Note: We should be only doing this if `cache_context=True` is set, but if
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# it isn't then the code will raise an exception when its called anyway, so
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# its not the end of the world.
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# it's not the end of the world.
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context_arg_index = None
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for idx, name in enumerate(signature.arg_names):
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if name == "cache_context":
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@ -72,7 +112,7 @@ def cached_function_method_signature(ctx: MethodSigContext) -> CallableType:
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arg_names.pop(context_arg_index)
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arg_kinds.pop(context_arg_index)
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# Third, we add an optional "on_invalidate" argument.
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# 3. Add an optional "on_invalidate" argument.
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#
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# This is a either
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# - a callable which accepts no input and returns nothing, or
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@ -94,35 +134,16 @@ def cached_function_method_signature(ctx: MethodSigContext) -> CallableType:
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arg_names.append("on_invalidate")
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arg_kinds.append(ARG_NAMED_OPT) # Arg is an optional kwarg.
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# Finally we ensure the return type is a Deferred.
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if (
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isinstance(signature.ret_type, Instance)
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and signature.ret_type.type.fullname == "twisted.internet.defer.Deferred"
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):
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# If it is already a Deferred, nothing to do.
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ret_type = signature.ret_type
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else:
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ret_arg = None
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if isinstance(signature.ret_type, Instance):
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# If a coroutine, wrap the coroutine's return type in a Deferred.
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if signature.ret_type.type.fullname == "typing.Coroutine":
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ret_arg = signature.ret_type.args[2]
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# 4. Ensure the return type is a Deferred.
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ret_arg = _get_true_return_type(signature)
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# If an awaitable, wrap the awaitable's final value in a Deferred.
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elif signature.ret_type.type.fullname == "typing.Awaitable":
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ret_arg = signature.ret_type.args[0]
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# Otherwise, wrap the return value in a Deferred.
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if ret_arg is None:
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ret_arg = signature.ret_type
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# This should be able to use ctx.api.named_generic_type, but that doesn't seem
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# to find the correct symbol for anything more than 1 module deep.
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#
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# modules is not part of CheckerPluginInterface. The following is a combination
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# of TypeChecker.named_generic_type and TypeChecker.lookup_typeinfo.
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sym = ctx.api.modules["twisted.internet.defer"].names.get("Deferred") # type: ignore[attr-defined]
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ret_type = Instance(sym.node, [remove_instance_last_known_values(ret_arg)])
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# This should be able to use ctx.api.named_generic_type, but that doesn't seem
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# to find the correct symbol for anything more than 1 module deep.
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#
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# modules is not part of CheckerPluginInterface. The following is a combination
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# of TypeChecker.named_generic_type and TypeChecker.lookup_typeinfo.
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sym = ctx.api.modules["twisted.internet.defer"].names.get("Deferred") # type: ignore[attr-defined]
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ret_type = Instance(sym.node, [remove_instance_last_known_values(ret_arg)])
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signature = signature.copy_modified(
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arg_types=arg_types,
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@ -134,6 +155,198 @@ def cached_function_method_signature(ctx: MethodSigContext) -> CallableType:
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return signature
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def check_is_cacheable_wrapper(ctx: MethodSigContext) -> CallableType:
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"""Asserts that the signature of a method returns a value which can be cached.
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Makes no changes to the provided method signature.
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"""
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# The true signature, this isn't being modified so this is what will be returned.
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signature: CallableType = ctx.default_signature
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if not isinstance(ctx.args[0][0], TempNode):
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ctx.api.note("Cached function is not a TempNode?!", ctx.context) # type: ignore[attr-defined]
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return signature
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orig_sig = ctx.args[0][0].type
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if not isinstance(orig_sig, CallableType):
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ctx.api.fail("Cached 'function' is not a callable", ctx.context)
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return signature
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check_is_cacheable(orig_sig, ctx)
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return signature
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def check_is_cacheable(
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signature: CallableType,
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ctx: Union[MethodSigContext, FunctionSigContext],
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) -> None:
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"""
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Check if a callable returns a type which can be cached.
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Args:
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signature: The callable to check.
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ctx: The signature context, used for error reporting.
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"""
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# Unwrap the true return type from the cached function.
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return_type = _get_true_return_type(signature)
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verbose = ctx.api.options.verbosity >= 1
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# TODO Technically a cachedList only needs immutable values, but forcing them
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# to return Mapping instead of Dict is fine.
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ok, note = is_cacheable(return_type, signature, verbose)
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if ok:
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message = f"function {signature.name} is @cached, returning {return_type}"
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else:
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message = f"function {signature.name} is @cached, but has mutable return value {return_type}"
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if note:
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message += f" ({note})"
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message = message.replace("builtins.", "").replace("typing.", "")
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if ok and note:
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ctx.api.note(message, ctx.context) # type: ignore[attr-defined]
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elif not ok:
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ctx.api.fail(message, ctx.context, code=AT_CACHED_MUTABLE_RETURN)
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# Immutable simple values.
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IMMUTABLE_VALUE_TYPES = {
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"builtins.bool",
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"builtins.int",
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"builtins.float",
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"builtins.str",
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"builtins.bytes",
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}
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# Types defined in Synapse which are known to be immutable.
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IMMUTABLE_CUSTOM_TYPES = {
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"synapse.synapse_rust.acl.ServerAclEvaluator",
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"synapse.synapse_rust.push.FilteredPushRules",
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# This is technically not immutable, but close enough.
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"signedjson.types.VerifyKey",
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}
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# Immutable containers only if the values are also immutable.
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IMMUTABLE_CONTAINER_TYPES_REQUIRING_IMMUTABLE_ELEMENTS = {
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"builtins.frozenset",
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"builtins.tuple",
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"typing.AbstractSet",
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"typing.Sequence",
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"immutabledict.immutabledict",
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}
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MUTABLE_CONTAINER_TYPES = {
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"builtins.set",
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"builtins.list",
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"builtins.dict",
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}
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AT_CACHED_MUTABLE_RETURN = ErrorCode(
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"synapse-@cached-mutable",
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"@cached() should have an immutable return type",
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"General",
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)
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def is_cacheable(
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rt: mypy.types.Type, signature: CallableType, verbose: bool
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) -> Tuple[bool, Optional[str]]:
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"""
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Check if a particular type is cachable.
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A type is cachable if it is immutable; for complex types this recurses to
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check each type parameter.
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Returns: a 2-tuple (cacheable, message).
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- cachable: False means the type is definitely not cacheable;
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true means anything else.
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- Optional message.
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"""
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# This should probably be done via a TypeVisitor. Apologies to the reader!
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if isinstance(rt, AnyType):
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return True, ("may be mutable" if verbose else None)
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elif isinstance(rt, Instance):
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if (
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rt.type.fullname in IMMUTABLE_VALUE_TYPES
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or rt.type.fullname in IMMUTABLE_CUSTOM_TYPES
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):
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# "Simple" types are generally immutable.
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return True, None
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elif rt.type.fullname == "typing.Mapping":
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# Generally mapping keys are immutable, but they only *have* to be
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# hashable, which doesn't imply immutability. E.g. Mapping[K, V]
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# is cachable iff K and V are cachable.
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return is_cacheable(rt.args[0], signature, verbose) and is_cacheable(
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rt.args[1], signature, verbose
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)
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elif rt.type.fullname in IMMUTABLE_CONTAINER_TYPES_REQUIRING_IMMUTABLE_ELEMENTS:
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# E.g. Collection[T] is cachable iff T is cachable.
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return is_cacheable(rt.args[0], signature, verbose)
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elif rt.type.fullname in MUTABLE_CONTAINER_TYPES:
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# Mutable containers are mutable regardless of their underlying type.
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return False, None
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elif "attrs" in rt.type.metadata:
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# attrs classes are only cachable iff it is frozen (immutable itself)
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# and all attributes are cachable.
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frozen = rt.type.metadata["attrs"]["frozen"]
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if frozen:
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for attribute in rt.type.metadata["attrs"]["attributes"]:
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attribute_name = attribute["name"]
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symbol_node = rt.type.names[attribute_name].node
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assert isinstance(symbol_node, Var)
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assert symbol_node.type is not None
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ok, note = is_cacheable(symbol_node.type, signature, verbose)
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if not ok:
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return False, f"non-frozen attrs property: {attribute_name}"
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# All attributes were frozen.
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return True, None
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else:
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return False, "non-frozen attrs class"
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else:
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# Ensure we fail for unknown types, these generally means that the
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# above code is not complete.
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return (
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False,
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f"Don't know how to handle {rt.type.fullname} return type instance",
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)
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elif isinstance(rt, NoneType):
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# None is cachable.
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return True, None
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elif isinstance(rt, (TupleType, UnionType)):
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# Tuples and unions are cachable iff all their items are cachable.
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for item in rt.items:
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ok, note = is_cacheable(item, signature, verbose)
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if not ok:
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return False, note
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# This discards notes but that's probably fine
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return True, None
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elif isinstance(rt, TypeAliasType):
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# For a type alias, check if the underlying real type is cachable.
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return is_cacheable(mypy.types.get_proper_type(rt), signature, verbose)
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elif isinstance(rt, UninhabitedType) and rt.is_noreturn:
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# There is no return value, just consider it cachable. This is only used
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# in tests.
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return True, None
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else:
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# Ensure we fail for unknown types, these generally means that the
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# above code is not complete.
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return False, f"Don't know how to handle {type(rt).__qualname__} return type"
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def plugin(version: str) -> Type[SynapsePlugin]:
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# This is the entry point of the plugin, and lets us deal with the fact
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# that the mypy plugin interface is *not* stable by looking at the version
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@ -33,7 +33,7 @@ from synapse.api.errors import (
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RequestSendFailed,
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SynapseError,
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)
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from synapse.types import JsonDict, ThirdPartyInstanceID
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from synapse.types import JsonDict, JsonMapping, ThirdPartyInstanceID
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from synapse.util.caches.descriptors import _CacheContext, cached
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from synapse.util.caches.response_cache import ResponseCache
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@ -256,7 +256,7 @@ class RoomListHandler:
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cache_context: _CacheContext,
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with_alias: bool = True,
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allow_private: bool = False,
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) -> Optional[JsonDict]:
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) -> Optional[JsonMapping]:
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"""Returns the entry for a room
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Args:
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@ -182,6 +182,7 @@ class UserPushAction(EmailPushAction):
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profile_tag: str
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# TODO This is used as a cached value and is mutable.
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@attr.s(slots=True, auto_attribs=True)
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class NotifCounts:
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"""
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@ -193,7 +194,7 @@ class NotifCounts:
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highlight_count: int = 0
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@attr.s(slots=True, auto_attribs=True)
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@attr.s(slots=True, frozen=True, auto_attribs=True)
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class RoomNotifCounts:
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"""
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The per-user, per-room count of notifications. Used by sync and push.
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@ -201,7 +202,7 @@ class RoomNotifCounts:
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main_timeline: NotifCounts
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# Map of thread ID to the notification counts.
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threads: Dict[str, NotifCounts]
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threads: Mapping[str, NotifCounts]
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@staticmethod
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def empty() -> "RoomNotifCounts":
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|
@ -483,7 +484,7 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
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return room_to_count
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@cached(tree=True, max_entries=5000, iterable=True)
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@cached(tree=True, max_entries=5000, iterable=True) # type: ignore[synapse-@cached-mutable]
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async def get_unread_event_push_actions_by_room_for_user(
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self,
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room_id: str,
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|
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@ -458,7 +458,7 @@ class RelationsWorkerStore(SQLBaseStore):
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)
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return result is not None
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@cached()
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@cached() # type: ignore[synapse-@cached-mutable]
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async def get_references_for_event(self, event_id: str) -> List[JsonDict]:
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raise NotImplementedError()
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@ -512,11 +512,12 @@ class RelationsWorkerStore(SQLBaseStore):
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"_get_references_for_events_txn", _get_references_for_events_txn
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)
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@cached()
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@cached() # type: ignore[synapse-@cached-mutable]
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def get_applicable_edit(self, event_id: str) -> Optional[EventBase]:
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raise NotImplementedError()
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@cachedList(cached_method_name="get_applicable_edit", list_name="event_ids")
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# TODO: This returns a mutable object, which is generally bad.
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@cachedList(cached_method_name="get_applicable_edit", list_name="event_ids") # type: ignore[synapse-@cached-mutable]
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async def get_applicable_edits(
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self, event_ids: Collection[str]
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) -> Mapping[str, Optional[EventBase]]:
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|
@ -598,11 +599,12 @@ class RelationsWorkerStore(SQLBaseStore):
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for original_event_id in event_ids
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}
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@cached()
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@cached() # type: ignore[synapse-@cached-mutable]
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def get_thread_summary(self, event_id: str) -> Optional[Tuple[int, EventBase]]:
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raise NotImplementedError()
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@cachedList(cached_method_name="get_thread_summary", list_name="event_ids")
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# TODO: This returns a mutable object, which is generally bad.
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@cachedList(cached_method_name="get_thread_summary", list_name="event_ids") # type: ignore[synapse-@cached-mutable]
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async def get_thread_summaries(
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self, event_ids: Collection[str]
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) -> Mapping[str, Optional[Tuple[int, EventBase]]]:
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|
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|
@ -275,7 +275,7 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
|
|||
_get_users_in_room_with_profiles,
|
||||
)
|
||||
|
||||
@cached(max_entries=100000)
|
||||
@cached(max_entries=100000) # type: ignore[synapse-@cached-mutable]
|
||||
async def get_room_summary(self, room_id: str) -> Mapping[str, MemberSummary]:
|
||||
"""Get the details of a room roughly suitable for use by the room
|
||||
summary extension to /sync. Useful when lazy loading room members.
|
||||
|
@ -1071,7 +1071,8 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
|
|||
)
|
||||
return {row["event_id"]: row["membership"] for row in rows}
|
||||
|
||||
@cached(max_entries=10000)
|
||||
# TODO This returns a mutable object, which is generally confusing when using a cache.
|
||||
@cached(max_entries=10000) # type: ignore[synapse-@cached-mutable]
|
||||
def _get_joined_hosts_cache(self, room_id: str) -> "_JoinedHostsCache":
|
||||
return _JoinedHostsCache()
|
||||
|
||||
|
|
|
@ -45,6 +45,7 @@ class ProfileInfo:
|
|||
display_name: Optional[str]
|
||||
|
||||
|
||||
# TODO This is used as a cached value and is mutable.
|
||||
@attr.s(slots=True, frozen=True, weakref_slot=False, auto_attribs=True)
|
||||
class MemberSummary:
|
||||
# A truncated list of (user_id, event_id) tuples for users of a given
|
||||
|
|
|
@ -36,6 +36,8 @@ from typing import (
|
|||
)
|
||||
from weakref import WeakValueDictionary
|
||||
|
||||
import attr
|
||||
|
||||
from twisted.internet import defer
|
||||
from twisted.python.failure import Failure
|
||||
|
||||
|
@ -466,6 +468,35 @@ class _CacheContext:
|
|||
)
|
||||
|
||||
|
||||
@attr.s(auto_attribs=True, slots=True, frozen=True)
|
||||
class _CachedFunctionDescriptor:
|
||||
"""Helper for `@cached`, we name it so that we can hook into it with mypy
|
||||
plugin."""
|
||||
|
||||
max_entries: int
|
||||
num_args: Optional[int]
|
||||
uncached_args: Optional[Collection[str]]
|
||||
tree: bool
|
||||
cache_context: bool
|
||||
iterable: bool
|
||||
prune_unread_entries: bool
|
||||
name: Optional[str]
|
||||
|
||||
def __call__(self, orig: F) -> CachedFunction[F]:
|
||||
d = DeferredCacheDescriptor(
|
||||
orig,
|
||||
max_entries=self.max_entries,
|
||||
num_args=self.num_args,
|
||||
uncached_args=self.uncached_args,
|
||||
tree=self.tree,
|
||||
cache_context=self.cache_context,
|
||||
iterable=self.iterable,
|
||||
prune_unread_entries=self.prune_unread_entries,
|
||||
name=self.name,
|
||||
)
|
||||
return cast(CachedFunction[F], d)
|
||||
|
||||
|
||||
def cached(
|
||||
*,
|
||||
max_entries: int = 1000,
|
||||
|
@ -476,9 +507,8 @@ def cached(
|
|||
iterable: bool = False,
|
||||
prune_unread_entries: bool = True,
|
||||
name: Optional[str] = None,
|
||||
) -> Callable[[F], CachedFunction[F]]:
|
||||
func = lambda orig: DeferredCacheDescriptor(
|
||||
orig,
|
||||
) -> _CachedFunctionDescriptor:
|
||||
return _CachedFunctionDescriptor(
|
||||
max_entries=max_entries,
|
||||
num_args=num_args,
|
||||
uncached_args=uncached_args,
|
||||
|
@ -489,7 +519,26 @@ def cached(
|
|||
name=name,
|
||||
)
|
||||
|
||||
return cast(Callable[[F], CachedFunction[F]], func)
|
||||
|
||||
@attr.s(auto_attribs=True, slots=True, frozen=True)
|
||||
class _CachedListFunctionDescriptor:
|
||||
"""Helper for `@cachedList`, we name it so that we can hook into it with mypy
|
||||
plugin."""
|
||||
|
||||
cached_method_name: str
|
||||
list_name: str
|
||||
num_args: Optional[int] = None
|
||||
name: Optional[str] = None
|
||||
|
||||
def __call__(self, orig: F) -> CachedFunction[F]:
|
||||
d = DeferredCacheListDescriptor(
|
||||
orig,
|
||||
cached_method_name=self.cached_method_name,
|
||||
list_name=self.list_name,
|
||||
num_args=self.num_args,
|
||||
name=self.name,
|
||||
)
|
||||
return cast(CachedFunction[F], d)
|
||||
|
||||
|
||||
def cachedList(
|
||||
|
@ -498,7 +547,7 @@ def cachedList(
|
|||
list_name: str,
|
||||
num_args: Optional[int] = None,
|
||||
name: Optional[str] = None,
|
||||
) -> Callable[[F], CachedFunction[F]]:
|
||||
) -> _CachedListFunctionDescriptor:
|
||||
"""Creates a descriptor that wraps a function in a `DeferredCacheListDescriptor`.
|
||||
|
||||
Used to do batch lookups for an already created cache. One of the arguments
|
||||
|
@ -527,16 +576,13 @@ def cachedList(
|
|||
def batch_do_something(self, first_arg, second_args):
|
||||
...
|
||||
"""
|
||||
func = lambda orig: DeferredCacheListDescriptor(
|
||||
orig,
|
||||
return _CachedListFunctionDescriptor(
|
||||
cached_method_name=cached_method_name,
|
||||
list_name=list_name,
|
||||
num_args=num_args,
|
||||
name=name,
|
||||
)
|
||||
|
||||
return cast(Callable[[F], CachedFunction[F]], func)
|
||||
|
||||
|
||||
def _get_cache_key_builder(
|
||||
param_names: Sequence[str],
|
||||
|
|
Loading…
Reference in New Issue