Fixed a bug where non-existent optional dependencies can result in a cascading load failure.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@36213 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/ExtensionFinder.java

@@ -157,6 +157,11 @@ public abstract class ExtensionFinder implements ExtensionPoint {
                         if(instance!=null)
                             result.add(new ExtensionComponent<T>(type.cast(instance),item.annotation()));
                     }
+                } catch (LinkageError e) {
+                    // sometimes the instantiation fails in an indirect classloading failure,
+                    // which results in a LinkageError
+                    LOGGER.log(item.annotation().optional() ? Level.FINE : Level.WARNING,
+                               "Failed to load "+item.className(), e);
                 } catch (InstantiationException e) {
                     LOGGER.log(item.annotation().optional() ? Level.FINE : Level.WARNING,
                                "Failed to load "+item.className(), e);