Improve error message for absence of indices (#39789)

"no indices exist" has been added to the error message for absence of indices

Author: Eunovo

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

@@ -157,10 +157,19 @@ Index[] concreteIndices(Context context, String... indexExpressions) {
         for (ExpressionResolver expressionResolver : expressionResolvers) {
             expressions = expressionResolver.resolve(context, expressions);
         }
-
+        
         if (expressions.isEmpty()) {
             if (!options.allowNoIndices()) {
-                IndexNotFoundException infe = new IndexNotFoundException((String)null);
+                IndexNotFoundException infe;
+                if (indexExpressions.length == 1) {
+                    if (indexExpressions[0].equals(MetaData.ALL)) {
+                        infe = new IndexNotFoundException("no indices exist", (String)null);
+                    } else {
+                        infe = new IndexNotFoundException((String)null);
+                    }
+                } else {
+                    infe = new IndexNotFoundException((String)null);
+                }
                 infe.setResources("index_expression", indexExpressions);
                 throw infe;
             } else {
@@ -173,7 +182,12 @@ Index[] concreteIndices(Context context, String... indexExpressions) {
             AliasOrIndex aliasOrIndex = metaData.getAliasAndIndexLookup().get(expression);
             if (aliasOrIndex == null ) {
                 if (failNoIndices) {
-                    IndexNotFoundException infe = new IndexNotFoundException(expression);
+                    IndexNotFoundException infe;
+                    if (expression.equals(MetaData.ALL)) {
+                        infe = new IndexNotFoundException("no indices exist", expression);
+                    } else {
+                        infe = new IndexNotFoundException(expression);  
+                    }
                     infe.setResources("index_expression", expression);
                     throw infe;
                 } else {

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

@@ -580,7 +580,26 @@ public void testConcreteIndicesIgnoreIndicesEmptyRequest() {
         assertThat(newHashSet(indexNameExpressionResolver.concreteIndexNames(context, new String[]{})),
             equalTo(newHashSet("kuku", "testXXX")));
     }
+    public void testConcreteIndicesNoIndicesErrorMessage() {
+        MetaData.Builder mdBuilder = MetaData.builder();
+        ClusterState state = ClusterState.builder(new ClusterName("_name")).metaData(mdBuilder).build();
+        IndexNameExpressionResolver.Context context = new IndexNameExpressionResolver.Context(state, 
+            IndicesOptions.fromOptions(false, false, true, true));
+        IndexNotFoundException infe = expectThrows(IndexNotFoundException.class,
+                () -> indexNameExpressionResolver.concreteIndices(context, new String[]{}));
+        assertThat(infe.getMessage(), is("no such index [null] and no indices exist"));
+    }
 
+    public void testConcreteIndicesNoIndicesErrorMessageNoExpand() {
+        MetaData.Builder mdBuilder = MetaData.builder();
+        ClusterState state = ClusterState.builder(new ClusterName("_name")).metaData(mdBuilder).build();
+        IndexNameExpressionResolver.Context context = new IndexNameExpressionResolver.Context(state, 
+            IndicesOptions.fromOptions(false, false, false, false));
+        IndexNotFoundException infe = expectThrows(IndexNotFoundException.class,
+                () -> indexNameExpressionResolver.concreteIndices(context, new String[]{}));
+        assertThat(infe.getMessage(), is("no such index [_all] and no indices exist"));
+    }
+    
     public void testConcreteIndicesWildcardExpansion() {
         MetaData.Builder mdBuilder = MetaData.builder()
                 .put(indexBuilder("testXXX").state(State.OPEN))

server/src/test/java/org/elasticsearch/validate/SimpleValidateQueryIT.java

@@ -160,7 +160,7 @@ public void testValidateEmptyCluster() {
             client().admin().indices().prepareValidateQuery().get();
             fail("Expected IndexNotFoundException");
         } catch (IndexNotFoundException e) {
-            assertThat(e.getMessage(), is("no such index [null]"));
+            assertThat(e.getMessage(), is("no such index [null] and no indices exist"));
         }
     }