42 lines
1.3 KiB
Python
42 lines
1.3 KiB
Python
from functools import partial
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class BaseMiddleware:
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"""
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Base class for implementing ASGI middleware. Inherit from this and
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override the setup() method if you want to do things before you
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get to.
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Note that subclasses of this are not self-safe; don't store state on
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the instance, as it serves multiple application instances. Instead, use
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scope.
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"""
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def __init__(self, inner):
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"""
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Middleware constructor - just takes inner application.
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"""
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self.inner = inner
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def __call__(self, scope):
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"""
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ASGI constructor; can insert things into the scope, but not
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run asynchronous code.
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"""
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# Copy scope to stop changes going upstream
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scope = dict(scope)
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# Allow subclasses to change the scope
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self.populate_scope(scope)
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# Call the inner application's init
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inner_instance = self.inner(scope)
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# Partially bind it to our coroutine entrypoint along with the scope
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return partial(self.coroutine_call, inner_instance, scope)
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async def coroutine_call(self, inner_instance, scope, receive, send):
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"""
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ASGI coroutine; where we can resolve items in the scope
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(but you can't modify it at the top level here!)
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"""
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await self.resolve_scope(scope)
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await inner_instance(receive, send)
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