fix single artifact message generation when there is dependencies.

Author: stonier

gradle_plugins/src/main/groovy/org/ros/gradle_plugins/CatkinPlugin.groovy

@@ -160,6 +160,29 @@ class CatkinPackage {
         p.tasks.compileJava.source generateSourcesTask.outputs.files
     }
 
+    def void generateUnofficialMessageArtifact(Project p) {
+        /* Couple of constraints here:
+             1) maven group forced to org.ros.rosjava_messages to that all message artifact
+                dependencies are easily found.
+             2) Open ended dependency range (takes the latest in ROS_PACKAGE_PATH) since we
+                don't know the artifact versions the user really wants.
+        */
+        p.version = version
+        p.group = 'org.ros.rosjava_messages'
+        p.dependencies.add("compile", 'org.ros.rosjava_bootstrap:message_generation:[0.2,0.3)')
+        messageDependencies().each { d ->
+            p.dependencies.add("compile", 'org.ros.rosjava_messages:' + d + ':[0.1,)')
+        }
+        def generatedSourcesDir = "${p.buildDir}/generated-src"
+        def generateSourcesTask = p.tasks.create("generateSources", JavaExec)
+        generateSourcesTask.description = "Generate sources for " + name
+        generateSourcesTask.outputs.dir(p.file(generatedSourcesDir))
+        generateSourcesTask.args = new ArrayList<String>([generatedSourcesDir, name])
+        generateSourcesTask.classpath = p.configurations.runtime
+        generateSourcesTask.main = 'org.ros.internal.message.GenerateInterfaces'
+        p.tasks.compileJava.source generateSourcesTask.outputs.files
+    }
+
     /*
      * Hack to work around for rosjava_test_msgs - look in a subfolder for the
      * msgs and name the artifact by the subfolder name/version.