Fix missing order field in TemplatesMetadata deserialization (opensearch-project#15509)

Signed-off-by: Sooraj Sinha <soosinha@amazon.com>

Author: soosinha

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

@@ -133,16 +133,15 @@ public static TemplatesMetadata fromXContent(XContentParser parser) throws IOExc
             String currentFieldName = parser.currentName();
             if (currentFieldName == null) {
                 token = parser.nextToken();
-                if (token == XContentParser.Token.START_OBJECT) {
-                    // move to the field name
-                    token = parser.nextToken();
-                }
-                currentFieldName = parser.currentName();
             }
-            if (currentFieldName != null) {
-                while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
+            if (token == XContentParser.Token.START_OBJECT) {
+                // move to the field name
+                token = parser.nextToken();
+            }
+            if (parser.currentName() != null && token != XContentParser.Token.END_OBJECT) {
+                do {
                     builder.put(IndexTemplateMetadata.Builder.fromXContent(parser, parser.currentName()));
-                }
+                } while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT);
             }
             return builder.build();
         }

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

@@ -1536,6 +1536,41 @@ public static Metadata randomMetadata() {
         return md.build();
     }
 
+    public void testXContentWithTemplateMetadata() throws IOException {
+        final TemplatesMetadata templatesMetadata = getTemplatesMetadata(0);
+        verifyTemplatesMetadata(templatesMetadata);
+        final TemplatesMetadata templatesMetadata2 = getTemplatesMetadata(2);
+        verifyTemplatesMetadata(templatesMetadata2);
+    }
+
+    private void verifyTemplatesMetadata(TemplatesMetadata templatesMetadata) throws IOException {
+        final Metadata originalMeta = Metadata.builder().templates(templatesMetadata).build();
+        final XContentBuilder builder = JsonXContent.contentBuilder();
+        builder.startObject();
+        Metadata.FORMAT.toXContent(builder, originalMeta);
+        builder.endObject();
+        try (XContentParser parser = createParser(JsonXContent.jsonXContent, BytesReference.bytes(builder))) {
+            final Metadata fromXContentMeta = Metadata.fromXContent(parser);
+            assertThat(fromXContentMeta.templates(), equalTo(originalMeta.templates()));
+        }
+    }
+
+    private static TemplatesMetadata getTemplatesMetadata(int numberOfTemplates) {
+        TemplatesMetadata.Builder builder = TemplatesMetadata.builder();
+        for (int i = 0; i < numberOfTemplates; i++) {
+            builder.put(
+                IndexTemplateMetadata.builder("template" + i)
+                    .order(1234)
+                    .patterns(Arrays.asList(randomAlphaOfLength(3) + "-*"))
+                    .settings(
+                        Settings.builder().put("index.random_index_setting_" + randomAlphaOfLength(3), randomAlphaOfLength(5)).build()
+                    )
+                    .build()
+            );
+        }
+        return builder.build();
+    }
+
     private static CreateIndexResult createIndices(int numIndices, int numBackingIndices, String dataStreamName) {
         // create some indices that do not back a data stream
         final List<Index> indices = new ArrayList<>();

server/src/test/java/org/opensearch/gateway/remote/model/RemoteTemplatesMetadataTests.java

@@ -231,12 +231,22 @@ public static TemplatesMetadata getTemplatesMetadata() {
         return TemplatesMetadata.builder()
             .put(
                 IndexTemplateMetadata.builder("template" + randomAlphaOfLength(3))
+                    .order(1234)
                     .patterns(Arrays.asList("bar-*", "foo-*"))
                     .settings(
                         Settings.builder().put("index.random_index_setting_" + randomAlphaOfLength(3), randomAlphaOfLength(5)).build()
                     )
                     .build()
             )
+            .put(
+                IndexTemplateMetadata.builder("template" + randomAlphaOfLength(3))
+                    .order(5678)
+                    .patterns(Arrays.asList("test-*"))
+                    .settings(
+                        Settings.builder().put("index.random_index_setting_" + randomAlphaOfLength(3), randomAlphaOfLength(5)).build()
+                    )
+                    .build()
+            )
             .build();
     }
 }