Watcher: Return proper GetWatchResponse if watcher index is missing (elastic/x-pack-elasticsearch#1462)

This ensures that the same responses is returned, when a watch is
missing and when the whole watch index is missing for the
GetWatchResponse.

relates elastic/x-pack-elasticsearch#1409

Original commit: elastic/x-pack-elasticsearch@88a7335fa9

plugin/src/main/java/org/elasticsearch/xpack/watcher/transport/actions/get/TransportGetWatchAction.java

@@ -12,6 +12,7 @@ import org.elasticsearch.common.inject.Inject;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentType;
+import org.elasticsearch.index.IndexNotFoundException;
 import org.elasticsearch.license.XPackLicenseState;
 import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.TransportService;
@@ -64,6 +65,13 @@ public class TransportGetWatchAction extends WatcherTransportAction<GetWatchRequ
             } else {
                 listener.onResponse(new GetWatchResponse(request.getId()));
             }
-        }, listener::onFailure));
+        }, e -> {
+            // special case. This API should not care if the index is missing or not, it should respond with the watch not being found
+            if (e instanceof IndexNotFoundException) {
+                listener.onResponse(new GetWatchResponse(request.getId()));
+            } else {
+                listener.onFailure(e);
+            }
+        }));
     }
 }

plugin/src/test/java/org/elasticsearch/xpack/watcher/transport/action/get/GetWatchTests.java

@@ -22,7 +22,6 @@ import static org.elasticsearch.xpack.watcher.client.WatchSourceBuilders.watchBu
 import static org.elasticsearch.xpack.watcher.input.InputBuilders.simpleInput;
 import static org.elasticsearch.xpack.watcher.trigger.TriggerBuilders.schedule;
 import static org.elasticsearch.xpack.watcher.trigger.schedule.Schedules.interval;
-import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.hasKey;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.not;
@@ -55,16 +54,14 @@ public class GetWatchTests extends AbstractWatcherIntegrationTestCase {
         assertThat(source, not(hasKey("status")));
     }
 
-    public void testGetNotFoundOnNonExistingIndex() throws Exception {
-        // ensure index/alias is deleted, test infra might have created it automatically
+    public void testGetNotFound() throws Exception {
+        // does not matter if the watch does not exist or the index does not exist, we expect the same response
+        if (randomBoolean()) {
             try {
                 assertAcked(client().admin().indices().prepareDelete(Watch.INDEX));
             } catch (IndexNotFoundException e) {}
-        Exception e = expectThrows(Exception.class, () -> watcherClient().getWatch(new GetWatchRequest("_name")).get());
-        assertThat(e.getMessage(), containsString("no such index"));
         }
 
-    public void testGetNotFound() throws Exception {
         GetWatchResponse getResponse = watcherClient().getWatch(new GetWatchRequest("_name")).get();
         assertThat(getResponse, notNullValue());
         assertThat(getResponse.getId(), is("_name"));

plugin/src/test/resources/rest-api-spec/test/watcher/get_watch/20_missing.yml

@@ -1,5 +1,5 @@
 ---
-"Test get watch api with missing watch":
+"Test get watch api with missing watch on existing index":
   - do:
       cluster.health:
           wait_for_status: yellow
@@ -17,3 +17,21 @@
         id: "missing_watch"
   - match: { found : false}
   - match: { _id: "missing_watch" }
+
+---
+"Test get watch api with missing watch on missing index":
+  - do:
+      cluster.health:
+          wait_for_status: yellow
+
+  - do:
+      indices.delete:
+        index: .watches*
+        ignore: 404
+
+  - do:
+      catch: missing
+      xpack.watcher.get_watch:
+        id: "missing_watch"
+  - match: { found : false}
+  - match: { _id: "missing_watch" }