Fix plugins being able to introduce new Metabase namespaces (credit: @alexuf)

src/metabase/util.clj

@@ -768,15 +768,15 @@
 (def metabase-namespace-symbols
   "Delay to a vector of symbols of all Metabase namespaces, excluding test namespaces.
    This is intended for use by various routines that load related namespaces, such as task and events initialization.
-   Using `ns-find/find-namespaces` is fairly slow, and can take as much as half a second to iterate over the thousand or so
-   namespaces that are part of the Metabase project; use this instead for a massive performance increase."
-  ;; Actually we can go ahead and start doing this in the background once the app launches while other stuff is loading, so use a future here
-  ;; This would be faster when running the *JAR* if we just did it at compile-time and made it ^:const, but that would inhibit the "plugin system"
-  ;; from loading "plugin" namespaces at launch if they're on the classpath
-  (future (vec (for [ns-symb (ns-find/find-namespaces (classpath/system-classpath))
-                     :when   (and (.startsWith (name ns-symb) "metabase.")
-                                  (not (.contains (name ns-symb) "test")))]
-                 ns-symb))))
+   Using `ns-find/find-namespaces` is fairly slow, and can take as much as half a second to iterate over the thousand
+   or so namespaces that are part of the Metabase project; use this instead for a massive performance increase."
+  ;; We want to give JARs in the ./plugins directory a chance to load. At one point we have this as a future so it
+  ;; start looking for things in the background while other stuff is happening but that meant plugins couldn't
+  ;; introduce new Metabase namespaces such as drivers.
+  (delay (vec (for [ns-symb (ns-find/find-namespaces (classpath/system-classpath))
+                    :when   (and (.startsWith (name ns-symb) "metabase.")
+                                 (not (.contains (name ns-symb) "test")))]
+                ns-symb))))
 
 (def ^:const ^java.util.regex.Pattern uuid-regex
   "A regular expression for matching canonical string representations of UUIDs."