Added help-allowEmptyArchive.html. Did some cleanup in ArtifactArchiver and config.jelly

core/src/main/java/hudson/tasks/ArtifactArchiver.java

@@ -41,6 +41,7 @@ import java.io.File;
 import java.io.IOException;
 
 import net.sf.json.JSONObject;
+import javax.annotation.Nonnull;
 
 /**
  * Copies the artifacts into an archive directory.
@@ -67,14 +68,9 @@ public class ArtifactArchiver extends Recorder {
     /**
      * Fail (or not) the build if archiving returns nothing.
      */
+    @Nonnull
     private Boolean allowEmptyArchive;
 
-    /**
-     * Compatibility for systems using the older setting.
-     */
-    private static final Boolean allowEmptyArchiveSystemProp =
-            Boolean.getBoolean(ArtifactArchiver.class.getName()+".warnOnEmpty");
-
     @DataBoundConstructor
     public ArtifactArchiver(String artifacts, String excludes, boolean latestOnly, boolean allowEmptyArchive) {
         this.artifacts = artifacts.trim();
@@ -86,7 +82,7 @@ public class ArtifactArchiver extends Recorder {
     // Backwards compatibility for older builds
     public Object readResolve() {
         if (allowEmptyArchive == null) {
-            this.allowEmptyArchive = allowEmptyArchiveSystemProp;
+            this.allowEmptyArchive = Boolean.getBoolean(ArtifactArchiver.class.getName()+".warnOnEmpty");
         }
         return this;
     }

core/src/main/resources/hudson/tasks/ArtifactArchiver/config.jelly

@@ -31,10 +31,10 @@ THE SOFTWARE.
     <f:entry title="${%Excludes}" field="excludes">
       <f:textbox />
     </f:entry>
-    <f:entry title="" field="latestOnly" >
+    <f:entry field="latestOnly" >
       <f:checkbox title="${%lastBuildOnly}"/>
     </f:entry>
-    <f:entry title="" field="allowEmptyArchive" >
+    <f:entry field="allowEmptyArchive" >
       <f:checkbox title="${%allowEmptyArchive}"/>
     </f:entry>
   </f:advanced>

core/src/main/resources/hudson/tasks/ArtifactArchiver/help-allowEmptyArchive.html

+<div>
+    Normally, a build fails if archiving returns zero artifacts.
+    This option allows the archiving process to return nothing without failing the build.
+    Instead, the build will simply throw a warning.
+</div>
\ No newline at end of file