Support external versioning for deletes arriving before initial update, closes elastic#1351.

Author: kimchy

modules/elasticsearch/src/main/java/org/elasticsearch/index/engine/robin/RobinEngine.java

@@ -635,7 +635,8 @@ private void innerDelete(Delete delete, IndexWriter writer) throws IOException {
                         updatedVersion = currentVersion < 0 ? 1 : currentVersion + 1;
                     } else { // External
                         if (currentVersion == -1) {
-                            throw new VersionConflictEngineException(shardId, delete.type(), delete.id(), -1, delete.version());
+                            // its an external version, that's fine, we allow it to be set
+                            //throw new VersionConflictEngineException(shardId, delete.type(), delete.id(), -1, delete.version());
                         } else if (currentVersion >= delete.version()) {
                             throw new VersionConflictEngineException(shardId, delete.type(), delete.id(), currentVersion, delete.version());
                         }

modules/test/integration/src/test/java/org/elasticsearch/test/integration/versioning/SimpleVersioningTests.java

@@ -61,6 +61,24 @@ public class SimpleVersioningTests extends AbstractNodesTests {
         closeAllNodes();
     }
 
+    @Test public void testExternalVersioningInitialDelete() throws Exception {
+        client.admin().indices().prepareDelete().execute().actionGet();
+
+        client.admin().indices().prepareCreate("test").execute().actionGet();
+        client.admin().cluster().prepareHealth("test").setWaitForGreenStatus().execute().actionGet();
+
+        DeleteResponse deleteResponse = client2.prepareDelete("test", "type", "1").setVersion(17).setVersionType(VersionType.EXTERNAL).execute().actionGet();
+        assertThat(deleteResponse.notFound(), equalTo(true));
+
+        try {
+            client.prepareIndex("test", "type", "1").setSource("field1", "value1_1").setVersion(13).setVersionType(VersionType.EXTERNAL).execute().actionGet();
+        } catch (ElasticSearchException e) {
+            assertThat(e.unwrapCause(), instanceOf(VersionConflictEngineException.class));
+        }
+
+        client.prepareIndex("test", "type", "1").setSource("field1", "value1_1").setVersion(18).setVersionType(VersionType.EXTERNAL).execute().actionGet();
+    }
+
     @Test public void testExternalVersioning() throws Exception {
         try {
             client.admin().indices().prepareDelete("test").execute().actionGet();