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import logging |
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from contextlib import ExitStack |
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from copy import copy |
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from typing import ( |
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Collection, |
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Union, |
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Type, |
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TypeVar, |
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Optional, |
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cast, |
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ContextManager, |
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Iterator, |
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Generator, |
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Callable, |
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List, |
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) |
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from lagom import Container |
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from lagom.compilaton import mypyc_attr |
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from lagom.definitions import ConstructionWithContainer, SingletonWrapper, Alias |
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from lagom.exceptions import InvalidDependencyDefinition |
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from lagom.interfaces import ( |
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ReadableContainer, |
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SpecialDepDefinition, |
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CallTimeContainerUpdate, |
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) |
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X = TypeVar("X") |
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@mypyc_attr(allow_interpreted_subclasses=True) |
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class ContextContainer(Container): |
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""" |
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Wraps a regular container but is a ContextManager for use within a `with`. |
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>>> from tests.examples import SomeClass, SomeClassManager |
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>>> from lagom import Container |
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>>> from typing import ContextManager |
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>>> |
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>>> # The regular container |
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>>> c = Container() |
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>>> |
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>>> # register a context manager for SomeClass |
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>>> c[ContextManager[SomeClass]] = SomeClassManager |
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>>> |
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>>> context_c = ContextContainer(c, context_types=[SomeClass]) |
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>>> with context_c: |
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... context_c[SomeClass] |
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<tests.examples.SomeClass object at ...> |
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""" |
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exit_stack: Optional[ExitStack] = None |
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_context_types: Collection[Type] |
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_context_singletons: Collection[Type] |
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def __init__( |
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self, |
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container: Container, |
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context_types: Collection[Type], |
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context_singletons: Collection[Type] = tuple(), |
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log_undefined_deps: Union[bool, logging.Logger] = False, |
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): |
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self._context_types = context_types |
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self._context_singletons = context_singletons |
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super().__init__(container, log_undefined_deps) |
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def clone(self) -> "ContextContainer": |
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"""returns a copy of the container |
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:return: |
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""" |
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return ContextContainer( |
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self, |
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context_types=self._context_types, |
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context_singletons=self._context_singletons, |
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log_undefined_deps=self._undefined_logger, |
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) |
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def __enter__(self): |
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if not self.exit_stack: |
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# All actual context definitions happen on a clone so that there's isolation between invocations |
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in_context = self.clone() |
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for dep_type in set(self._context_types): |
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in_context[dep_type] = self._context_type_def(dep_type) |
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for dep_type in set(self._context_singletons): |
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in_context[dep_type] = self._singleton_type_def(dep_type) |
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in_context.exit_stack = ExitStack() |
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# The parent context manager keeps track of the inner clone |
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self.exit_stack = ExitStack() |
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self.exit_stack.enter_context(in_context) |
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return in_context |
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return self |
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def __exit__(self, exc_type, exc_val, exc_tb): |
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if self.exit_stack: |
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self.exit_stack.close() |
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self.exit_stack = None |
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def partial( |
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self, |
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func: Callable[..., X], |
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shared: List[Type] = None, |
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container_updater: Optional[CallTimeContainerUpdate] = None, |
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) -> Callable[..., X]: |
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def _with_context(*args, **kwargs): |
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with self as c: |
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# TODO: Try and move this partial outside the function as this is expensive |
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base_partial = super(ContextContainer, c).partial( |
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func, shared, container_updater |
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) |
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return base_partial(*args, **kwargs) |
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return _with_context |
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def magic_partial( |
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self, |
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func: Callable[..., X], |
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shared: List[Type] = None, |
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keys_to_skip: List[str] = None, |
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skip_pos_up_to: int = 0, |
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container_updater: Optional[CallTimeContainerUpdate] = None, |
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) -> Callable[..., X]: |
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def _with_context(*args, **kwargs): |
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with self as c: |
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# TODO: Try and move this partial outside the function as this is expensive |
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base_partial = super(ContextContainer, c).magic_partial( |
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func, shared, keys_to_skip, skip_pos_up_to, container_updater |
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) |
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return base_partial(*args, **kwargs) |
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return _with_context |
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def _context_type_def(self, dep_type: Type): |
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type_def = self.get_definition(ContextManager[dep_type]) or self.get_definition(Iterator[dep_type]) or self.get_definition(Generator[dep_type, None, None]) # type: ignore |
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if type_def is None: |
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raise InvalidDependencyDefinition( |
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f"A ContextManager[{dep_type}] should be defined. " |
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f"This could be an Iterator[{dep_type}] or Generator[{dep_type}, None, None] " |
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f"with the @contextmanager decorator" |
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) |
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if isinstance(type_def, Alias): |
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# Without this we create a definition that points to |
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# itself. |
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type_def = copy(type_def) |
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type_def.skip_definitions = True |
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return ConstructionWithContainer(lambda c: self._context_resolver(c, type_def)) # type: ignore |
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def _singleton_type_def(self, dep_type: Type): |
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""" |
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The same as context_type_def but acts as a singleton within this container |
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""" |
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return SingletonWrapper(self._context_type_def(dep_type)) |
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def _context_resolver(self, c: ReadableContainer, type_def: SpecialDepDefinition): |
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""" |
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Takes an existing definition which must be a context manager. Returns |
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the value of the context manager from __enter__ and then places the |
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__exit__ in this container's exit stack |
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""" |
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assert self.exit_stack, "Types can only be resolved within a with" |
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context_manager = cast(ContextManager, type_def.get_instance(c)) |
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return self.exit_stack.enter_context(context_manager) |
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meadsteve /
lagom
