Cleanup warnings for missing getPlugin() null checks (#5222)

core/src/main/java/hudson/ClassicPluginStrategy.java

@@ -390,7 +390,7 @@ public class ClassicPluginStrategy implements PluginStrategy {
 
             // initialize plugin
             try {
-                Plugin plugin = wrapper.getPlugin();
+                Plugin plugin = wrapper.getPluginOrFail();
                 plugin.setServletContext(pluginManager.context);
                 startPlugin(wrapper);
             } catch(Throwable t) {
@@ -403,7 +403,7 @@ public class ClassicPluginStrategy implements PluginStrategy {
     }
 
     public void startPlugin(PluginWrapper plugin) throws Exception {
-        plugin.getPlugin().start();
+        plugin.getPluginOrFail().start();
     }
 
     @Override

core/src/main/java/hudson/PluginManager.java

@@ -572,7 +572,7 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
                                     return;
                                 }
                                 try {
-                                    p.getPlugin().postInitialize();
+                                    p.getPluginOrFail().postInitialize();
                                 } catch (Exception e) {
                                     failedPlugins.add(new FailedPlugin(p.getShortName(), e));
                                     activePlugins.remove(p);
@@ -980,7 +980,9 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
             throw new IOException("Failed to refresh extensions after installing some plugins", e);
         }
         for (PluginWrapper p : plugins) {
-          p.getPlugin().postInitialize();
+            //TODO:According to the postInitialize() documentation, one may expect that
+            //p.getPluginOrFail() NPE will continue the initialization. Keeping the original behavior ATM
+          p.getPluginOrFail().postInitialize();
         }
 
         // run initializers in the added plugins
@@ -1707,6 +1709,7 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
         return installJobs;
     }
 
+    @CheckForNull
     private UpdateSite.Plugin getPlugin(String pluginName, String siteName) {
         UpdateSite updateSite = Jenkins.get().getUpdateCenter().getById(siteName);
         if (updateSite == null) {

core/src/main/java/hudson/PluginWrapper.java

@@ -523,12 +523,25 @@ public class PluginWrapper implements Comparable<PluginWrapper>, ModelObject {
 
     /**
      * Gets the instance of {@link Plugin} contributed by this plugin.
+     * @return Plugin instace or {@code null} if it is not present in the plugin instance store.
      */
     public @CheckForNull Plugin getPlugin() {
         PluginInstanceStore pis = Jenkins.lookup(PluginInstanceStore.class);
         return pis != null ? pis.store.get(this) : null;
     }
 
+    /**
+     * Gets the instance of {@link Plugin} contributed by this plugin.
+     * @throws Exception no plugin in the {@link PluginInstanceStore}
+     */
+    public @NonNull Plugin getPluginOrFail() throws Exception {
+        Plugin plugin = getPlugin();
+        if (plugin == null) {
+            throw new Exception("Cannot find the plugin instance: " + shortName);
+        }
+        return plugin;
+    }
+
     /**
      * Gets the URL that shows more information about this plugin.
      * @return

core/src/main/java/hudson/model/UpdateSite.java

@@ -411,8 +411,9 @@ public class UpdateSite {
      *      The short name of the plugin. Corresponds to {@link PluginWrapper#getShortName()}.
      *
      * @return
-     *      null if no such information is found.
+     *      {@code null} if no such information is found.
      */
+    @CheckForNull
     public Plugin getPlugin(String artifactId) {
         Data dt = getData();
         if(dt==null)    return null;

core/src/main/java/jenkins/model/GlobalPluginConfiguration.java

@@ -2,6 +2,7 @@ package jenkins.model;
 
 import hudson.Extension;
 import hudson.Plugin;
+import hudson.PluginWrapper;
 import hudson.StructuredForm;
 import net.sf.json.JSONObject;
 import org.jenkinsci.Symbol;
@@ -23,11 +24,18 @@ public class GlobalPluginConfiguration  extends GlobalConfiguration {
     @Override
     public boolean configure(StaplerRequest req, JSONObject json) throws FormException {
         try {
-            for( JSONObject o : StructuredForm.toList(json, "plugin"))
-                Jenkins.get().pluginManager.getPlugin(o.getString("name")).getPlugin().configure(req, o);
+            for( JSONObject o : StructuredForm.toList(json, "plugin")) {
+                String pluginName = o.getString("name");
+                PluginWrapper pw = Jenkins.get().pluginManager.getPlugin(pluginName);
+                Plugin p = pw != null ? pw.getPlugin() : null;
+                if (p == null) {
+                    throw new FormException("Cannot find the plugin instance: " + pluginName, "plugin");
+                }
+                p.configure(req, o);
+            }
             return true;
         } catch (IOException | ServletException e) {
-            throw new FormException(e,"plugin");
+            throw new FormException(e, "plugin");
         }
     }
 }