To add a middleware that’s already available on the server’s classpath, it’s as
simple as sending the message
However, if the middleware is loaded, it’s very likely that it hasn’t been included
as a dependency on the server, and thus unavailable on its classpath. Furthermore.
In this case, we can use the
dynamic-loader in conjunction with the
;; handle sideloading separatedly...
;; now we add the middleware
;; confirm it's being loaded..
;; and we should get something like...
:middleware [... "#'cider.nrepl.middleware/wrap-version" ...]}
However, if we tried to use the middleware with an
cider-version op, we’d get an
error, because the middleware is implemented in a different namespace, which is
only loaded on the first use of the
cider-version op. This is a practice in
many middleware to improve startup performance. One method of getting around this
is to request the extra namespace to be loaded at
add-middleware time too:
;; after starting the sideloader...
;; now, the following should work
There is no operation to remove a single middleware, but it’s possible to reset
the stack to a baseline with the
swap-middleware operation. If the goal is to
simply reset the middleware stack, use this in conjunction with
Also note that updating the middleware stack may also destroy/re-create middleware state. As an example, sideloading would need to be re-started. The impact on each middleware differs, however, as some of them, e.g.
session holds their state globally.