cors: Don't return an error for preflight requests with non-matching origin #224
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jplatte
changed the title
… unless it's a closure, in which case this is of course impossible.
Moves the work of concatenating multiple origins to layer construction time (from layer call time).
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Depends on #219, will rebase after merge.
This PR contains behavioral changes.
This is the third and final preliminary refactoring for the implementation of the new CORS API I proposed in #194 (comment).
Motivation
As far as my understanding goes, there is no good reason to return an error status code when a preflight request is made from an origin that isn't configured to be allowed (since this whole thing is a browser-side security feature).
Solution
Just return the configured list of allowed origins or in case a closure is set, an empty list, on origin "mismatch". This should make the CORS middleware a lot more predictable and improve the debugging experience in cases where you haven't gotten the CORS rules correct yet.