Providing a documented abstraction for Items.updatingByXml.

(Turns out cloudbees-template at least needs this, and it is possible other things besides Trigger could use it too.)

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

@@ -34,6 +34,7 @@ import hudson.cli.declarative.CLIMethod;
 import hudson.cli.declarative.CLIResolver;
 import hudson.model.listeners.ItemListener;
 import hudson.model.listeners.SaveableListener;
+import hudson.remoting.Callable;
 import hudson.security.AccessControlled;
 import hudson.security.Permission;
 import hudson.security.ACL;
@@ -593,12 +594,12 @@ public abstract class AbstractItem extends Actionable implements Item, HttpDelet
 
             // try to reflect the changes by reloading
             new XmlFile(Items.XSTREAM, out.getTemporaryFile()).unmarshal(this);
-            Items.updatingByXml.set(true);
-            try {
-                onLoad(getParent(), getRootDir().getName());
-            } finally {
-                Items.updatingByXml.set(false);
-            }
+            Items.whileUpdatingByXml(new Callable<Void,IOException>() {
+                @Override public Void call() throws IOException {
+                    onLoad(getParent(), getRootDir().getName());
+                    return null;
+                }
+            });
             Jenkins.getInstance().rebuildDependencyGraphAsync();
 
             // if everything went well, commit this new version

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

@@ -326,8 +326,9 @@ public abstract class AbstractProject<P extends AbstractProject<P,R>,R extends A
         }
         this.builds = builds;
         triggers().setOwner(this);
-        for (Trigger t : triggers())
-            t.start(this, Items.updatingByXml.get());
+        for (Trigger t : triggers()) {
+            t.start(this, Items.currentlyUpdatingByXml());
+        }
         if(scm==null)
             scm = new NullSCM(); // perhaps it was pointing to a plugin that no longer exists.
 

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

@@ -25,6 +25,7 @@ package hudson.model;
 
 import hudson.Util;
 import hudson.model.listeners.ItemListener;
+import hudson.remoting.Callable;
 import hudson.security.AccessControlled;
 import hudson.util.CopyOnWriteMap;
 import hudson.util.Function1;
@@ -206,12 +207,12 @@ public abstract class ItemGroupMixIn {
         Util.copyFile(Items.getConfigFile(src).getFile(),Items.getConfigFile(result).getFile());
 
         // reload from the new config
-        Items.updatingByXml.set(true);
-        try {
-            result = (T)Items.load(parent,result.getRootDir());
-        } finally {
-            Items.updatingByXml.set(false);
-        }
+        final File rootDir = result.getRootDir();
+        result = Items.whileUpdatingByXml(new Callable<T,IOException>() {
+            @Override public T call() throws IOException {
+                return (T) Items.load(parent, rootDir);
+            }
+        });
         result.onCopiedFrom(src);
 
         add(result);
@@ -231,18 +232,17 @@ public abstract class ItemGroupMixIn {
 
         // place it as config.xml
         File configXml = Items.getConfigFile(getRootDirFor(name)).getFile();
-        configXml.getParentFile().mkdirs();
+        final File dir = configXml.getParentFile();
+        dir.mkdirs();
         try {
             IOUtils.copy(xml,configXml);
 
             // load it
-            TopLevelItem result;
-            Items.updatingByXml.set(true);
-            try {
-                result = (TopLevelItem)Items.load(parent,configXml.getParentFile());
-            } finally {
-                Items.updatingByXml.set(false);
-            }
+            TopLevelItem result = Items.whileUpdatingByXml(new Callable<TopLevelItem,IOException>() {
+                @Override public TopLevelItem call() throws IOException {
+                    return (TopLevelItem) Items.load(parent, dir);
+                }
+            });
             add(result);
 
             ItemListener.fireOnCreated(result);
@@ -251,7 +251,7 @@ public abstract class ItemGroupMixIn {
             return result;
         } catch (IOException e) {
             // if anything fails, delete the config file to avoid further confusion
-            Util.deleteRecursive(configXml.getParentFile());
+            Util.deleteRecursive(dir);
             throw e;
         }
     }

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

@@ -30,6 +30,7 @@ import hudson.matrix.MatrixProject;
 import hudson.matrix.MatrixConfiguration;
 import hudson.XmlFile;
 import hudson.matrix.Axis;
+import hudson.remoting.Callable;
 import hudson.triggers.Trigger;
 import hudson.util.DescriptorList;
 import hudson.util.EditDistance;
@@ -61,12 +62,41 @@ public class Items {
      * @see Trigger#start
      * @since 1.482
      */
-    static final ThreadLocal<Boolean> updatingByXml = new ThreadLocal<Boolean>() {
+    private static final ThreadLocal<Boolean> updatingByXml = new ThreadLocal<Boolean>() {
         @Override protected Boolean initialValue() {
             return false;
         }
     };
 
+    /**
+     * Runs a block while making {@link #currentlyUpdatingByXml} be temporarily true.
+     * Use this when you are creating or changing an item.
+     * @param <V> a return value type (may be {@link Void})
+     * @param <T> an error type (may be {@link Error})
+     * @param callable a block, typically running {@link #load} or {@link Item#onLoad}
+     * @return whatever {@code callable} returned
+     * @throws T anything {@code callable} throws
+     * @since 1.546
+     */
+    public static <V,T extends Throwable> V whileUpdatingByXml(Callable<V,T> callable) throws T {
+        updatingByXml.set(true);
+        try {
+            return callable.call();
+        } finally {
+            updatingByXml.set(false);
+        }
+    }
+
+    /**
+     * Checks whether we are in the middle of creating or configuring an item via XML.
+     * Used to determine the {@code newInstance} parameter for {@link Trigger#start}.
+     * @return true if {@link #whileUpdatingByXml} is currently being called, false for example when merely starting Jenkins or reloading from disk
+     * @since 1.546
+     */
+    public static boolean currentlyUpdatingByXml() {
+        return updatingByXml.get();
+    }
+
     /**
      * Returns all the registered {@link TopLevelItemDescriptor}s.
      */

core/src/main/java/hudson/triggers/Trigger.java

@@ -58,6 +58,7 @@ import java.util.logging.Logger;
 import antlr.ANTLRException;
 import javax.annotation.CheckForNull;
 import edu.umd.cs.findbugs.annotations.SuppressWarnings;
+import hudson.model.Items;
 
 /**
  * Triggers a {@link Build}.
@@ -78,6 +79,7 @@ public abstract class Trigger<J extends Item> implements Describable<Trigger<?>>
      * @param newInstance
      *      True if this may be a newly created trigger first attached to the {@link Project} (generally if the project is being created or configured).
      *      False if this is invoked for a {@link Project} loaded from disk.
+     * @see Items#currentlyUpdatingByXml
      */
     public void start(J project, boolean newInstance) {
         this.job = project;