Defend against NPE when no pom is registered using the pom task prior to using the deploy task (fix for #138)

src/main/java/org/apache/maven/resolver/internal/ant/tasks/AbstractDistTask.java

@@ -130,13 +130,18 @@ private void validateArtifactGav(final Artifact artifact) {
                 version = artifactPom.getVersion();
             }
 
-            final Model model = getPom().getModel(this);
+            final Pom pom = getPom();
+            if (pom == null) {
+                throw new BuildException("You must specify the <pom file=\"...\"> element"
+                        + " to denote the descriptor for the artifacts");
+            }
+            final Model model = pom.getModel(this);
 
             if (!(model.getGroupId().equals(gid)
                     && model.getArtifactId().equals(aid)
                     && model.getVersion().equals(version))) {
                 throw new BuildException(
-                        "Artifact references different pom than it would be installed with: " + artifact.toString());
+                        "Artifact references different pom than it would be installed with: " + artifact);
             }
         }
     }

src/test/java/org/apache/maven/resolver/internal/ant/DeployTest.java

@@ -22,6 +22,7 @@
 import java.util.Arrays;
 
 import junit.framework.JUnit4TestAdapter;
+import org.apache.tools.ant.BuildException;
 import org.junit.Test;
 
 import static org.hamcrest.MatcherAssert.assertThat;
@@ -30,6 +31,7 @@
 import static org.hamcrest.Matchers.greaterThanOrEqualTo;
 import static org.hamcrest.Matchers.hasItemInArray;
 import static org.hamcrest.Matchers.lessThanOrEqualTo;
+import static org.junit.Assert.fail;
 
 /*
  * still missing:
@@ -96,4 +98,33 @@ private void assertUpdatedFile(long min, long max, File repoPath, String path) {
                 file.lastModified(),
                 allOf(greaterThanOrEqualTo(min), lessThanOrEqualTo(max)));
     }
+
+    /**
+     * Reproduces an NPE when a deploy <artifact> contains only a nested <pom/>.
+     * <pre>{@code
+     *   <repo:deploy>
+     *     <repo:artifact file="${artifact.file}">
+     *       <repo:pom file="${project.dir}/dummy-pom.xml"/>
+     *     </repo:artifact>
+     *     <repo:snapshotrepo refid="Snapshots"/>
+     *   </repo:deploy>
+     * }</pre>
+     * Current behavior: Ant build fails with a NullPointerException at the root cause.
+     * Once the deploy task supports this case or throws a clearer error, update the assertion accordingly.
+     */
+    @Test
+    public void testDeployOnlyNestedPomException() {
+        try {
+            executeTarget("testDeployOnlyNestedPomException");
+            fail("Expected the build to fail when deploying with only a nested <pom/> inside <artifact>.");
+        } catch (Exception e) {
+            Throwable cause = e;
+            while (cause.getCause() != null) {
+                cause = cause.getCause();
+            }
+            if (!(cause instanceof BuildException)) {
+                fail("Expected NullPointerException as root cause, but was: " + cause);
+            }
+        }
+    }
 }

src/test/resources/ant/Deploy/ant.xml

@@ -69,4 +69,26 @@
     </repo:deploy>
   </target>
 
+ <!--
+  Only a nested <pom/> inside <resolver:artifact>.
+  The DeployTest expects this target to fail with a BuildException.
+ -->
+  <target name="testDeployOnlyNestedPomException">
+    <property name="artifact.file" value="${build.dir}/dummy-artifact.jar"/>
+    <property name="temp.dir" value="${build.dir}/temp"/>
+    <property name="temp.content.file" value="${temp.dir}/content.txt"/>
+    <echo file="${temp.content.file}" append="false">
+      This is a test artifact content.
+    </echo>
+    <jar destfile="${artifact.file}">
+      <fileset dir="${temp.dir}">
+        <include name="content.txt"/>
+      </fileset>
+    </jar>
+    <repo:deploy>
+      <repo:artifact file="${artifact.file}">
+        <repo:pom file="${project.dir}/dummy-pom.xml"/>
+      </repo:artifact>
+    </repo:deploy>
+  </target>
 </project>