Improve error messages for _stats with closed indices

CHANGELOG.md

@@ -59,6 +59,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Enabled mockTelemetryPlugin for IT and fixed OOM issues ([#13054](https://github.com/opensearch-project/OpenSearch/pull/13054))
 - Fix implement mark() and markSupported() in class FilterStreamInput ([#13098](https://github.com/opensearch-project/OpenSearch/pull/13098))
 - Fix snapshot _status API to return correct status for partial snapshots ([#12812](https://github.com/opensearch-project/OpenSearch/pull/12812))
+- Improve the error messages for _stats with closed indices ([#13012](https://github.com/opensearch-project/OpenSearch/pull/13012))
 
 ### Security
 

modules/rank-eval/src/internalClusterTest/java/org/opensearch/index/rankeval/RankEvalRequestIT.java

@@ -345,7 +345,7 @@ public void testIndicesOptions() {
         request.indicesOptions(IndicesOptions.fromParameters("closed", null, null, "false", SearchRequest.DEFAULT_INDICES_OPTIONS));
         response = client().execute(RankEvalAction.INSTANCE, request).actionGet();
         assertEquals(1, response.getFailures().size());
-        assertThat(response.getFailures().get("amsterdam_query"), instanceOf(IndexClosedException.class));
+        assertThat(response.getFailures().get("amsterdam_query"), instanceOf(IllegalArgumentException.class));
 
         // test allow_no_indices
         request = new RankEvalRequest(task, new String[] { "bad*" });

server/src/main/java/org/opensearch/cluster/metadata/IndexNameExpressionResolver.java

@@ -380,7 +380,13 @@ private void checkSystemIndexAccess(Context context, Metadata metadata, Set<Inde
     private static boolean shouldTrackConcreteIndex(Context context, IndicesOptions options, IndexMetadata index) {
         if (index.getState() == IndexMetadata.State.CLOSE) {
             if (options.forbidClosedIndices() && options.ignoreUnavailable() == false) {
-                throw new IndexClosedException(index.getIndex());
+                if (options.expandWildcardsClosed() == true) {
+                    throw new IllegalArgumentException(
+                        "To expand [" + index.getState() + "] wildcard, please set forbid_closed_indices to `false`"
+                    );
+                } else {
+                    throw new IndexClosedException(index.getIndex());
+                }
             } else {
                 return options.forbidClosedIndices() == false && addIndex(index, context);
             }

server/src/test/java/org/opensearch/cluster/metadata/IndexNameExpressionResolverTests.java

@@ -352,6 +352,25 @@ public void testIndexOptionsWildcardExpansion() {
         assertEquals(1, results.length);
         assertThat(results, arrayContainingInAnyOrder(".hidden-closed"));
 
+        options = IndicesOptions.fromOptions(false, true, false, true, false, false, false, false);
+        context = new IndexNameExpressionResolver.Context(state, options, false);
+
+        results = indexNameExpressionResolver.concreteIndexNames(context, "foo*");
+        assertEquals(1, results.length);
+        assertEquals("foo", results[0]);
+
+        try {
+            options = IndicesOptions.fromOptions(false, true, false, true, false, true, false, false);
+            context = new IndexNameExpressionResolver.Context(state, options, false);
+
+            results = indexNameExpressionResolver.concreteIndexNames(context, "foo*");
+            assertEquals(1, results.length);
+            assertEquals("foo", results[0]);
+        } catch (IllegalArgumentException iae) {
+            String expectedMessage = "To expand [CLOSE] wildcard, please set forbid_closed_indices to `false`";
+            assertEquals(expectedMessage, iae.getMessage());
+        }
+
         // Only open
         options = IndicesOptions.fromOptions(false, true, true, false, false);
         context = new IndexNameExpressionResolver.Context(state, options, false);