Try to propagate contexvars from lifespan to endpoints #1257
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@graingert this is in reference to adriangb/di#1 (comment)
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adriangb
commented
Aug 4, 2021
adriangb
commented
Aug 4, 2021
starlette/routing.py
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| if self.user_ctx is not None: | ||
| current_ctx = contextvars.copy_context() | ||
| for cvar in self.user_ctx: | ||
| if cvar in current_ctx: | ||
| # not set by the user, skip to avoid modifying | ||
| # vars used by event loops, servers, etc. | ||
| continue | ||
| try: | ||
| if cvar.get() != self.user_ctx.get(cvar): | ||
| cvar.set(self.user_ctx.get(cvar)) | ||
| except LookupError: | ||
| cvar.set(self.user_ctx.get(cvar)) |
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I'm pretty sure this sort of copying back the context can be used to allow things run by run_in_threadpool to behave like if they were being called directly (which would solve issues FastAPI has with sync dependencies)
adriangb
commented
Aug 4, 2021
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| try: | ||
| from contextvars import Context, ContextVar, copy_context | ||
| except ImportError: # pragma: no cover | ||
| Context = object # type: ignore | ||
| ContextVar = copy_context = None # type: ignore |
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This module can be cleaned up better. I was trying to encapsulate all of the try: import contexvars checks into one module
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The goal is that, from a users perspective, it endpoints should be run as if they were a task being executed from within the `yield of a lifespan.