Fix: resolve our Clojure source dependencies first in the classpath (#17919)

In PR #17867 we have a namespace
named schema.core, but this namespace is taken by library prismatic/schema
already (see https://github.com/plumatic/schema/tree/master/src/cljc/schema), a
library used by our direct dependency on bidi 2.1.6. This leads to a broken
build where the ClojureScript compiler reports undeclared vars
(https://clojurescript.org/reference/compiler-options#warnings).

We change the order Java resolves dependencies via the classpath mechanism. We
now first resolve our own Clojure sources, and then project dependencies.

Author: ilmotta

nix/mobile/jsbundle/default.nix

@@ -67,9 +67,12 @@ stdenv.mkDerivation {
   '';
   buildPhase = ''
     # Assemble CLASSPATH from available clojure dependencies.
-    # We append 'src' so it can find the local sources.
-    export CLASS_PATH="$(find ${deps.clojure} \
-      -iname '*.jar' | tr '\n' ':')src"
+    # We prepend 'src' so it can find the local sources and prioritize
+    # our own namespaces over dependencies, given that indirect dependencies
+    # can also cause naming conflicts (e.g. prismatic/schema already uses
+    # namespace schema.core).
+    export CLASS_PATH="src:$(find ${deps.clojure} \
+      -iname '*.jar' | tr '\n' ':')"
 
     # target must be one of the builds defined in shadow-cljs.edn
     java -cp "$CLASS_PATH" clojure.main \