Added a hook to manipulate Launcher used during a build.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@14938 71c3de6d-444a-0410-be80-ed276b4c234a

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

@@ -215,7 +215,7 @@ public abstract class AbstractBuild<P extends AbstractProject<P,R>,R extends Abs
     protected abstract class AbstractRunner implements Runner {
         /**
          * Since configuration can be changed while a build is in progress,
-         * stick to one launcher and use it.
+         * create a launcher once and stick to it for the entire build duration.
          */
         protected Launcher launcher;
 
@@ -232,7 +232,7 @@ public abstract class AbstractBuild<P extends AbstractProject<P,R>,R extends Abs
             builtOn = node.getNodeName();
             hudsonVersion = Hudson.VERSION;
 
-            launcher = node.createLauncher(listener);
+            launcher = createLauncher(listener);
             if(node instanceof Slave)
                 listener.getLogger().println(Messages.AbstractBuild_BuildingRemotely(node.getNodeName()));
 
@@ -258,6 +258,17 @@ public abstract class AbstractBuild<P extends AbstractProject<P,R>,R extends Abs
             return result;
         }
 
+        /**
+         * Creates a {@link Launcher} that this build will use. This can be overridden by derived types
+         * to decorate the resulting {@link Launcher}.
+         *
+         * @param listener
+         *      Always non-null. Connected to the main build output. 
+         */
+        protected Launcher createLauncher(BuildListener listener) throws IOException, InterruptedException {
+            return getCurrentNode().createLauncher(listener);
+        }
+
         private void createSymLink(BuildListener listener, String name) throws InterruptedException {
             Util.createSymlink(getProject().getBuildDir(),"builds/"+getId(),"../"+name,listener);
         }

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

@@ -6,6 +6,7 @@ import hudson.tasks.BuildWrapper.Environment;
 import hudson.tasks.Builder;
 import hudson.tasks.BuildTrigger;
 import hudson.triggers.SCMTrigger;
+import hudson.Launcher;
 
 import java.io.File;
 import java.io.IOException;
@@ -128,6 +129,19 @@ public abstract class Build <P extends Project<P,B>,B extends Build<P,B>>
             return null;
         }
 
+        /**
+         * Decorates the {@link Launcher}
+         */
+        @Override
+        protected Launcher createLauncher(BuildListener listener) throws IOException, InterruptedException {
+            Launcher l = super.createLauncher(listener);
+
+            for(BuildWrapper bw : project.getBuildWrappers().values())
+                l = bw.decorateLauncher(Build.this,l,listener);
+
+            return l;
+        }
+
         public void post2(BuildListener listener) throws IOException, InterruptedException {
             performAllBuildStep(listener, project.getPublishers(),true);
             performAllBuildStep(listener, project.getProperties(),true);

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

@@ -9,6 +9,7 @@ import hudson.model.Describable;
 import hudson.model.Project;
 import hudson.model.Action;
 import hudson.model.AbstractProject;
+import hudson.model.Run.RunnerAbortedException;
 
 import java.io.IOException;
 import java.util.Map;
@@ -136,6 +137,38 @@ public abstract class BuildWrapper implements ExtensionPoint, Describable<BuildW
         throw new UnsupportedOperationException(getClass()+" needs to implement the setUp method");
     }
 
+    /**
+     * Provides an opportunity for a {@link BuildWrapper} to decorate a {@link Launcher} to be used in the build.
+     *
+     * <p>
+     * This hook is called very early on in the build (even before {@link #setUp(AbstractBuild, Launcher, BuildListener)} is invoked.)
+     * The typical use of {@link Launcher} decoration involves in modifying the environment that processes run,
+     * such as the use of sudo/pfexec/chroot, or manipulating environment variables.
+     *
+     * <p>
+     * The default implementation is no-op, which just returns the {@code listener} parameter as-is.
+     *
+     * @param build
+     *      The build in progress for which this {@link BuildWrapper} is called. Never null.
+     * @param launcher
+     *      The default launcher. Never null. This method is expected to wrap this launcher.
+     *      This makes sure that when multiple {@link BuildWrapper}s attempt to decorate the same launcher
+     *      it will sort of work. But if you are developing a plugin where such collision is not a concern,
+     *      you can also simply discard this {@link Launcher} and create an entirely different {@link Launcher}
+     *      and return it, too.
+     * @param listener
+     *      Connected to the build output. Never null. Can be used for error reporting.
+     * @return
+     *      Must not be null. If a fatal error happens, throw an exception.
+     * @throws RunnerAbortedException
+     *      If a fatal error is detected but the implementation handled it gracefully, throw this exception
+     *      to suppress stack trace.
+     * @since 1.280
+     */
+    public Launcher decorateLauncher(AbstractBuild build, Launcher launcher, BuildListener listener) throws IOException, InterruptedException, RunnerAbortedException {
+        return launcher;
+    }
+
     /**
      * {@link Action} to be displayed in the job page.
      *