3.2 library(http/http_dispatch): Dispatch requests in the HTTP server
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Availability::- use_module(library(http/http_dispatch)).
Sourcehttp_request_expansion(:Goal, +Rank:number)
Register Goal for expanding the HTTP request handler. Goal is called as below. If Goal fail the request is passed to the next expansion unmodified. 
call(Goal, Request0, Request, Options)

If multiple goals are registered they expand the request in a pipeline starting with the expansion hook with the lowest rank.

Besides rewriting the request, for example by validating the user identity based on HTTP authentication or cookies and adding this to the request, the hook may raise HTTP exceptions to indicate a bad request, permission error, etc. See http_status_reply/4.

Initially, auth_expansion/3 is registered with rank 100 to deal with the older http:authenticate/3 hook.