Use session classloader when loading deferred middleware

When loading CIDER middleware via the sideloader we need to make sure that extra
namespaces that are loaded later are also requested via the sideloader. The
original sideloader already provided a macro for
this (with-session-classloader), we just need to use it. This does mean that now
all our middlewares need to depend on the session middleware.

CHANGELOG.md

@@ -14,6 +14,7 @@
 ### Changes
 
 * Parallelize `cider.nrepl.middleware.stacktrace/analyze-stacktrace`.
+* [#705](https://github.com/clojure-emacs/cider-nrepl/pull/705): Use the session classloader when loading deferred middleware
 
 ## 0.26.0 (2021-04-22)
 

src/cider/nrepl.clj

@@ -15,6 +15,7 @@
    [nrepl.middleware.caught :refer [wrap-caught]]
    [nrepl.middleware.print :refer [wrap-print wrap-print-optional-arguments]]
    [nrepl.middleware.session :refer [session]]
+   [nrepl.misc :as misc :refer [with-session-classloader]]
    [nrepl.server :as nrepl-server]))
 
 ;;; Functionality for deferred middleware loading
@@ -43,12 +44,13 @@
 (defn- handler-future
   "Check whether a delay exists in the `delayed-handlers`. Otherwise make a delay
   out of `fn-name` and place it in the atom. "
-  [sym ns fn-name]
+  [sym ns fn-name session]
   (or (get @delayed-handlers sym)
       (get (swap! delayed-handlers assoc sym
                   (delay
                     (locking require-lock
-                      (require ns)
+                      (with-session-classloader session
+                        (require ns))
                       (resolve-or-fail fn-name))))
            sym)))
 
@@ -58,7 +60,7 @@
   [fn-name handler msg]
   (let [ns  (symbol (namespace `~fn-name))
         sym (symbol (name `~fn-name))]
-    `(@(handler-future '~sym '~ns '~fn-name)
+    `(@(handler-future '~sym '~ns '~fn-name (:session ~msg))
       ~handler ~msg)))
 
 (defmacro ^{:arglists '([name handler-fn descriptor]
@@ -79,7 +81,7 @@
                                   [descriptor trigger-it]
                                   [trigger-it descriptor])
         trigger-it (eval trigger-it)
-        descriptor (eval descriptor)
+        descriptor (update (eval descriptor) :requires (fnil conj #{}) #'nrepl.middleware.session/session)
         cond (if (or (nil? trigger-it) (set? trigger-it))
                (let [ops-set (into (-> descriptor :handles keys set) trigger-it)]
                  `(~ops-set (:op ~'msg)))