Empty mappings equals empty properties

docs/changelog/114624.yaml

@@ -0,0 +1,6 @@
+pr: 114624
+summary: Empty mappings equals empty properties
+area: Search
+type: enhancement
+issues:
+ - 107031

server/src/internalClusterTest/java/org/elasticsearch/action/admin/indices/create/CreateIndexIT.java

@@ -170,6 +170,22 @@ public void testTwoEmptyEqualMappings() throws Exception {
         assertEquals(fieldCapsResp1.get(), fieldCapsResp2.get());
     }
 
+    public void testEmptyMappingsEqualsEmptyProperties() throws Exception {
+        assertAcked(
+            prepareCreate("test1").setMapping(XContentFactory.jsonBuilder().startObject().startObject("properties").endObject().endObject())
+        );
+        assertAcked(prepareCreate("test2").setMapping(XContentFactory.jsonBuilder().startObject().endObject()));
+        FieldCapabilitiesRequest fieldCapsReq1 = new FieldCapabilitiesRequest();
+        fieldCapsReq1.indices("test1");
+        fieldCapsReq1.fields("*");
+        FieldCapabilitiesResponse fieldCapsResp1 = internalCluster().coordOnlyNodeClient().fieldCaps(fieldCapsReq1).actionGet();
+        FieldCapabilitiesRequest fieldCapsReq2 = new FieldCapabilitiesRequest();
+        fieldCapsReq2.indices("test2");
+        fieldCapsReq2.fields("*");
+        FieldCapabilitiesResponse fieldCapsResp2 = internalCluster().coordOnlyNodeClient().fieldCaps(fieldCapsReq2).actionGet();
+        assertEquals(fieldCapsResp1.get(), fieldCapsResp2.get());
+    }
+
     public void testInvalidShardCountSettings() throws Exception {
         int value = randomIntBetween(-10, 0);
         try {

server/src/main/java/org/elasticsearch/action/admin/indices/create/CreateIndexRequest.java

@@ -284,9 +284,9 @@ private CreateIndexRequest mapping(BytesReference source, XContentType xContentT
     }
 
     private CreateIndexRequest mapping(String type, Map<String, ?> source) {
-        if (source.isEmpty()) {
+        if (isSourceEffectivelyEmpty(source)) {
             // If no source is provided we return empty mappings
-            return mapping(EMPTY_MAPPINGS);
+            source = Map.of();
         } else if (source.size() != 1 || source.containsKey(type) == false) {
             // wrap it in a type map if its not
             source = Map.of(MapperService.SINGLE_MAPPING_NAME, source);
@@ -303,6 +303,27 @@ private CreateIndexRequest mapping(String type, Map<String, ?> source) {
         }
     }
 
+    /**
+     * Checks if the source map is effectively empty.
+     *
+     * @param source the source map to check
+     * @return true if the source map is empty or contains only an empty "properties" key, false otherwise
+     */
+    private boolean isSourceEffectivelyEmpty(Map<String, ?> source) {
+        if (source == null) {
+            return true;
+        }
+        if (source.isEmpty()) {
+            return true;
+        }
+        if (source.size() == 1 && source.containsKey("properties")) {
+            if (source.get("properties") instanceof Map<?, ?> properties) {
+                return properties.isEmpty();
+            }
+        }
+        return false;
+    }
+
     /**
      * The cause for this index creation.
      */