More helpful error message for ExtensionList.lookupSingleton (#8646)

jenkinsci · Oct 30, 2023 · 36de7a5 · 36de7a5
1 parent 6b0fab1
commit 36de7a5
Showing 1 changed file with 4 additions and 1 deletion.
diff --git a/core/src/main/java/hudson/ExtensionList.java b/core/src/main/java/hudson/ExtensionList.java
@@ -450,7 +450,10 @@ public static <T> ExtensionList<T> create(Jenkins jenkins, Class<T> type) {
      */
     public static @NonNull <U> U lookupSingleton(Class<U> type) {
         ExtensionList<U> all = lookup(type);
-        if (all.size() != 1) {
+        if (Main.isUnitTest && all.isEmpty()) {
+            throw new IllegalStateException("Found no instances of " + type.getName() +
+                " registered (possible annotation processor issue); try using `mvn clean test -Dtest=…` rather than an IDE test runner");
+        } else if (all.size() != 1) {
             throw new IllegalStateException("Expected 1 instance of " + type.getName() + " but got " + all.size());
         }
         return all.get(0);