Assign the right path to objects merged when parsing mappings (#89389)

When parsing mappings, we may find a field with same name specified twice, either
because JSON duplicate keys are allowed, or because a mix of object notation and dot
notation is used when providing mappings. The same can happen when applying dynamic
mappings as part of parsing an incoming document, as well as when merging separate
index templates that may contain the definition for the same field using a
mix of object notation and dot notation.

While we propagate the MapperBuilderContext across merge calls thanks to #86946, we do not
propagate the right context when we call merge on objects as part of parsing/building
mappings. This causes a situation in which the leaf fields that result from the merge
have the wrong path, which misses the first portion e.g. sub.field instead of obj.sub.field.

This commit applies the correct mapper builder context when building the object mapper builder
and two objects with same name are found.

Relates to #86946

Closes #88573

docs/changelog/89389.yaml

@@ -0,0 +1,6 @@
+pr: 89389
+summary: Assign the right path to objects merged when parsing mappings
+area: Mapping
+type: bug
+issues:
+ - 88573

server/src/internalClusterTest/java/org/elasticsearch/indices/template/SimpleIndexTemplateIT.java

@@ -14,6 +14,8 @@
 import org.elasticsearch.action.admin.indices.template.get.GetIndexTemplatesResponse;
 import org.elasticsearch.action.admin.indices.template.put.PutIndexTemplateRequestBuilder;
 import org.elasticsearch.action.bulk.BulkResponse;
+import org.elasticsearch.action.fieldcaps.FieldCapabilities;
+import org.elasticsearch.action.fieldcaps.FieldCapabilitiesResponse;
 import org.elasticsearch.action.index.IndexRequest;
 import org.elasticsearch.action.search.SearchResponse;
 import org.elasticsearch.cluster.ClusterState;
@@ -39,6 +41,7 @@
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 
 import static org.elasticsearch.action.support.WriteRequest.RefreshPolicy.IMMEDIATE;
@@ -1009,4 +1012,88 @@ public void testPartitionedTemplate() throws Exception {
         GetSettingsResponse getSettingsResponse = client().admin().indices().prepareGetSettings("test_good").get();
         assertEquals("6", getSettingsResponse.getIndexToSettings().get("test_good").get("index.routing_partition_size"));
     }
+
+    public void testIndexTemplatesWithSameSubfield() {
+        client().admin()
+            .indices()
+            .preparePutTemplate("template_1")
+            .setPatterns(Collections.singletonList("te*"))
+            .setSettings(indexSettings())
+            .setOrder(100)
+            .setMapping("""
+                {
+                  "_doc": {
+                    "properties": {
+                      "kwm": {
+                        "properties": {
+                          "source": {
+                            "properties": {
+                              "geo": {
+                                "properties": {
+                                  "location": {
+                                    "type": "geo_point"
+                                  }
+                                }
+                              }
+                            }
+                          }
+                        }
+                      },
+                      "source": {
+                        "properties": {
+                          "geo": {
+                            "properties": {
+                              "location": {
+                                "type": "geo_point"
+                              }
+                            }
+                          }
+                        }
+                      }
+                    }
+                  }
+                }
+                """, XContentType.JSON)
+            .get();
+
+        client().admin()
+            .indices()
+            .preparePutTemplate("template_2")
+            .setPatterns(Collections.singletonList("test*"))
+            .setSettings(indexSettings())
+            .setOrder(1)
+            .setMapping("""
+                {
+                  "_doc": {
+                    "properties": {
+                      "kwm.source.geo": {
+                        "properties": {
+                          "location": {
+                            "type": "geo_point"
+                          }
+                        }
+                      }
+                    }
+                  }
+                }
+                """, XContentType.JSON)
+            .get();
+
+        client().prepareIndex("test").setSource().get();
+        FieldCapabilitiesResponse fieldCapabilitiesResponse = client().prepareFieldCaps("test").setFields("*location").get();
+        {
+            Map<String, FieldCapabilities> field = fieldCapabilitiesResponse.getField("kwm.source.geo.location");
+            assertNotNull(field);
+            FieldCapabilities fieldCapabilities = field.get("geo_point");
+            assertTrue(fieldCapabilities.isSearchable());
+            assertTrue(fieldCapabilities.isAggregatable());
+        }
+        {
+            Map<String, FieldCapabilities> field = fieldCapabilitiesResponse.getField("source.geo.location");
+            assertNotNull(field);
+            FieldCapabilities fieldCapabilities = field.get("geo_point");
+            assertTrue(fieldCapabilities.isSearchable());
+            assertTrue(fieldCapabilities.isAggregatable());
+        }
+    }
 }

server/src/main/java/org/elasticsearch/index/mapper/NestedObjectMapper.java

@@ -170,7 +170,7 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
     }
 
     @Override
-    public ObjectMapper merge(Mapper mergeWith, MapperService.MergeReason reason, MapperBuilderContext mapperBuilderContext) {
+    public ObjectMapper merge(Mapper mergeWith, MapperService.MergeReason reason, MapperBuilderContext parentBuilderContext) {
         if ((mergeWith instanceof NestedObjectMapper) == false) {
             throw new IllegalArgumentException("can't merge a non nested mapping [" + mergeWith.name() + "] with a nested mapping");
         }
@@ -191,7 +191,7 @@ public ObjectMapper merge(Mapper mergeWith, MapperService.MergeReason reason, Ma
                 throw new MapperException("the [include_in_root] parameter can't be updated on a nested object mapping");
             }
         }
-        toMerge.doMerge(mergeWithObject, reason, mapperBuilderContext);
+        toMerge.doMerge(mergeWithObject, reason, parentBuilderContext);
         return toMerge;
     }
 

server/src/main/java/org/elasticsearch/index/mapper/ObjectMapper.java

@@ -150,6 +150,11 @@ protected final Map<String, Mapper> buildMappers(boolean root, MapperBuilderCont
                 assert mapper instanceof ObjectMapper == false || subobjects.value() : "unexpected object while subobjects are disabled";
                 Mapper existing = mappers.get(mapper.simpleName());
                 if (existing != null) {
+                    // The same mappings or document may hold the same field twice, either because duplicated JSON keys are allowed or
+                    // the same field is provided using the object notation as well as the dot notation at the same time.
+                    // This can also happen due to multiple index templates being merged into a single mappings definition using
+                    // XContentHelper#mergeDefaults, again in case some index templates contained mappings for the same field using a
+                    // mix of object notation and dot notation.
                     mapper = existing.merge(mapper, mapperBuilderContext);
                 }
                 mappers.put(mapper.simpleName(), mapper);
@@ -426,7 +431,11 @@ public void validate(MappingLookup mappers) {
         }
     }
 
-    public ObjectMapper merge(Mapper mergeWith, MergeReason reason, MapperBuilderContext mapperBuilderContext) {
+    protected MapperBuilderContext createChildContext(MapperBuilderContext mapperBuilderContext, String name) {
+        return mapperBuilderContext.createChildContext(name);
+    }
+
+    public ObjectMapper merge(Mapper mergeWith, MergeReason reason, MapperBuilderContext parentBuilderContext) {
         if ((mergeWith instanceof ObjectMapper) == false) {
             throw new IllegalArgumentException("can't merge a non object mapping [" + mergeWith.name() + "] with an object mapping");
         }
@@ -436,12 +445,11 @@ public ObjectMapper merge(Mapper mergeWith, MergeReason reason, MapperBuilderCon
         }
         ObjectMapper mergeWithObject = (ObjectMapper) mergeWith;
         ObjectMapper merged = clone();
-        merged.doMerge(mergeWithObject, reason, mapperBuilderContext);
+        merged.doMerge(mergeWithObject, reason, parentBuilderContext);
         return merged;
     }
 
-    protected void doMerge(final ObjectMapper mergeWith, MergeReason reason, MapperBuilderContext mapperBuilderContext) {
-
+    protected void doMerge(final ObjectMapper mergeWith, MergeReason reason, MapperBuilderContext parentBuilderContext) {
         if (mergeWith.dynamic != null) {
             this.dynamic = mergeWith.dynamic;
         }
@@ -462,6 +470,7 @@ protected void doMerge(final ObjectMapper mergeWith, MergeReason reason, MapperB
             }
         }
 
+        MapperBuilderContext objectBuilderContext = createChildContext(parentBuilderContext, simpleName());
         Map<String, Mapper> mergedMappers = null;
         for (Mapper mergeWithMapper : mergeWith) {
             Mapper mergeIntoMapper = (mergedMappers == null ? mappers : mergedMappers).get(mergeWithMapper.simpleName());
@@ -470,8 +479,7 @@ protected void doMerge(final ObjectMapper mergeWith, MergeReason reason, MapperB
             if (mergeIntoMapper == null) {
                 merged = mergeWithMapper;
             } else if (mergeIntoMapper instanceof ObjectMapper objectMapper) {
-                MapperBuilderContext childContext = mapperBuilderContext.createChildContext(objectMapper.simpleName());
-                merged = objectMapper.merge(mergeWithMapper, reason, childContext);
+                merged = objectMapper.merge(mergeWithMapper, reason, objectBuilderContext);
             } else {
                 assert mergeIntoMapper instanceof FieldMapper || mergeIntoMapper instanceof FieldAliasMapper;
                 if (mergeWithMapper instanceof ObjectMapper) {
@@ -485,7 +493,7 @@ protected void doMerge(final ObjectMapper mergeWith, MergeReason reason, MapperB
                 if (reason == MergeReason.INDEX_TEMPLATE) {
                     merged = mergeWithMapper;
                 } else {
-                    merged = mergeIntoMapper.merge(mergeWithMapper, mapperBuilderContext);
+                    merged = mergeIntoMapper.merge(mergeWithMapper, objectBuilderContext);
                 }
             }
             if (mergedMappers == null) {

server/src/main/java/org/elasticsearch/index/mapper/RootObjectMapper.java

@@ -322,13 +322,19 @@ RuntimeField getRuntimeField(String name) {
     }
 
     @Override
-    public RootObjectMapper merge(Mapper mergeWith, MergeReason reason, MapperBuilderContext mapperBuilderContext) {
-        return (RootObjectMapper) super.merge(mergeWith, reason, mapperBuilderContext);
+    protected MapperBuilderContext createChildContext(MapperBuilderContext mapperBuilderContext, String name) {
+        assert mapperBuilderContext == MapperBuilderContext.ROOT;
+        return mapperBuilderContext;
     }
 
     @Override
-    protected void doMerge(ObjectMapper mergeWith, MergeReason reason, MapperBuilderContext mapperBuilderContext) {
-        super.doMerge(mergeWith, reason, mapperBuilderContext);
+    public RootObjectMapper merge(Mapper mergeWith, MergeReason reason, MapperBuilderContext parentBuilderContext) {
+        return (RootObjectMapper) super.merge(mergeWith, reason, parentBuilderContext);
+    }
+
+    @Override
+    protected void doMerge(ObjectMapper mergeWith, MergeReason reason, MapperBuilderContext parentBuilderContext) {
+        super.doMerge(mergeWith, reason, parentBuilderContext);
         RootObjectMapper mergeWithObject = (RootObjectMapper) mergeWith;
         if (mergeWithObject.numericDetection.explicit()) {
             this.numericDetection = mergeWithObject.numericDetection;

server/src/test/java/org/elasticsearch/index/mapper/DocumentParserTests.java

@@ -33,6 +33,7 @@
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
@@ -2351,6 +2352,61 @@ public void testDocumentDescriptionInTsdb() throws IOException {
         }
     }
 
+    public void testMergeSubfieldWhileBuildingMappers() throws Exception {
+        MapperService mapperService = createMapperService();
+        /*
+        We had a bug (https://github.com/elastic/elasticsearch/issues/88573) building an object mapper (ObjectMapper.Builder#buildMappers).
+        A sub-field that already exists is merged with the existing one. As a result, the leaf field would get the wrong field path
+        (missing the first portion of its path). The only way to trigger this scenario for dynamic mappings is to either allow duplicate
+        JSON keys or ingest the same field with dots collapsed as well as expanded within the same document. Note that the two fields with
+        same name need to be part  of the same mappings (hence the same document). If they are in two distinct mappings they are properly
+        merged as part of RootObjectMapper#merge.
+         */
+        ParsedDocument doc = mapperService.documentMapper().parse(source("""
+            {
+              "foo" : {
+                "bar" : {
+                  "baz" : 1
+                }
+              },
+              "foo.bar.baz" : 2
+            }
+            """));
+        Mapping mapping = doc.dynamicMappingsUpdate();
+        assertNotNull(mapping);
+        Mapper fooMapper = mapping.getRoot().getMapper("foo");
+        assertNotNull(fooMapper);
+        assertTrue(fooMapper instanceof ObjectMapper);
+        Mapper barMapper = ((ObjectMapper) fooMapper).getMapper("bar");
+        assertTrue(barMapper instanceof ObjectMapper);
+        Mapper baz = ((ObjectMapper) barMapper).getMapper("baz");
+        assertNotNull(baz);
+        assertEquals("foo.bar.baz", baz.name());
+        assertEquals("baz", baz.simpleName());
+        IndexableField[] fields = doc.rootDoc().getFields("foo.bar.baz");
+        assertEquals(4, fields.length);
+        long[] longs = Arrays.stream(fields).mapToLong(value -> value.numericValue().longValue()).toArray();
+        assertArrayEquals(new long[] { 1, 1, 2, 2 }, longs);
+
+        // merge without going through toXContent and reparsing, otherwise the potential leaf path issue gets fixed on its own
+        Mapping newMapping = MapperService.mergeMappings(mapperService.documentMapper(), mapping, MapperService.MergeReason.MAPPING_UPDATE);
+        DocumentMapper newDocMapper = new DocumentMapper(mapperService.documentParser(), newMapping, newMapping.toCompressedXContent());
+        ParsedDocument doc2 = newDocMapper.parse(source("""
+            {
+              "foo" : {
+                "bar" : {
+                  "baz" : 10
+                }
+              }
+            }
+            """));
+        assertNull(doc2.dynamicMappingsUpdate());
+        IndexableField[] fields2 = doc2.rootDoc().getFields("foo.bar.baz");
+        assertEquals(2, fields2.length);
+        long[] longs2 = Arrays.stream(fields2).mapToLong(value -> value.numericValue().longValue()).toArray();
+        assertArrayEquals(new long[] { 10, 10 }, longs2);
+    }
+
     /**
      * Mapper plugin providing a mock metadata field mapper implementation that supports setting its value
      */

server/src/test/java/org/elasticsearch/index/mapper/MapperServiceTests.java

@@ -8,8 +8,10 @@
 
 package org.elasticsearch.index.mapper;
 
+import org.apache.lucene.index.IndexableField;
 import org.elasticsearch.Version;
 import org.elasticsearch.cluster.metadata.IndexMetadata;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.compress.CompressedXContent;
 import org.elasticsearch.common.settings.Settings;
@@ -353,4 +355,68 @@ public void testMultiFieldChecks() throws IOException {
         assertFalse(mapperService.isMultiField("object.subfield1"));
     }
 
+    public void testMergeObjectSubfieldWhileParsing() throws IOException {
+        /*
+        If we are parsing mappings that hold the definition of the same field twice, the two are merged together. This can happen when
+        mappings have the same field specified using the object notation as well as the dot notation, as well as when applying index
+        templates, in which case the two definitions may come from separate index templates that end up in the same map (through
+        XContentHelper#mergeDefaults, see MetadataCreateIndexService#parseV1Mappings).
+        We had a bug (https://github.com/elastic/elasticsearch/issues/88573) triggered by this scenario that caused the merged leaf fields
+        to get the wrong path (missing the first portion).
+         */
+        MapperService mapperService = createMapperService("""
+            {
+              "_doc": {
+                "properties": {
+                  "obj": {
+                    "properties": {
+                      "sub": {
+                        "properties": {
+                          "string": {
+                            "type": "keyword"
+                          }
+                        }
+                      }
+                    }
+                  },
+                  "obj.sub.string" : {
+                    "type" : "keyword"
+                  }
+                }
+              }
+            }
+            """);
+
+        assertNotNull(mapperService.mappingLookup().getMapper("obj.sub.string"));
+        MappedFieldType fieldType = mapperService.mappingLookup().getFieldType("obj.sub.string");
+        assertNotNull(fieldType);
+        assertEquals("""
+            {
+              "_doc" : {
+                "properties" : {
+                  "obj" : {
+                    "properties" : {
+                      "sub" : {
+                        "properties" : {
+                          "string" : {
+                            "type" : "keyword"
+                          }
+                        }
+                      }
+                    }
+                  }
+                }
+              }
+            }""", Strings.toString(mapperService.documentMapper().mapping(), true, true));
+
+        // check that with the resulting mappings a new document has the previously merged field indexed properly
+        ParsedDocument parsedDocument = mapperService.documentMapper().parse(source("""
+            {
+              "obj.sub.string" : "value"
+            }"""));
+
+        assertNull(parsedDocument.dynamicMappingsUpdate());
+        IndexableField[] fields = parsedDocument.rootDoc().getFields("obj.sub.string");
+        assertEquals(2, fields.length);
+    }
 }