Hacking: More intermediate types for path mapping

fix issues with property path vs mongo path mapping by introducing segments that can represent various combinations

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/QueryMapper.java

@@ -36,7 +36,6 @@ import org.bson.BsonValue;
 import org.bson.Document;
 import org.bson.conversions.Bson;
 import org.bson.types.ObjectId;
-
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.data.annotation.Reference;
@@ -57,14 +56,9 @@ import org.springframework.data.mongodb.core.aggregation.AggregationExpression;
 import org.springframework.data.mongodb.core.aggregation.RelaxedTypeBasedAggregationOperationContext;
 import org.springframework.data.mongodb.core.convert.MappingMongoConverter.NestedDocument;
 import org.springframework.data.mongodb.core.mapping.FieldName;
-import org.springframework.data.mongodb.core.mapping.MongoPath.MappedMongoPath;
-import org.springframework.data.mongodb.core.mapping.MongoPath.MappedMongoPath.MappedSegment;
 import org.springframework.data.mongodb.core.mapping.MongoPath;
 import org.springframework.data.mongodb.core.mapping.MongoPath.PathSegment;
 import org.springframework.data.mongodb.core.mapping.MongoPaths;
-import org.springframework.data.mongodb.core.mapping.MongoPath.RawMongoPath;
-import org.springframework.data.mongodb.core.mapping.MongoPath.RawMongoPath.Segment;
-import org.springframework.data.mongodb.core.mapping.MongoPath.RawMongoPath.TargetType;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
 import org.springframework.data.mongodb.core.query.Query;
@@ -1140,7 +1134,8 @@ public class QueryMapper {
 	 */
 	@Nullable
 	public PropertyPath toPropertyPath(
-		MongoPath mongoPath, MongoPersistentEntity<?> persistentEntity) {
+
+			MongoPath mongoPath, MongoPersistentEntity<?> persistentEntity) {
 
 		StringBuilder path = new StringBuilder();
 		MongoPersistentEntity<?> entity = persistentEntity;
@@ -1184,7 +1179,6 @@ public class QueryMapper {
 		return PropertyPath.from(path.toString(), persistentEntity.getType());
 	}
 
-
 	/**
 	 * Extension of {@link Field} to be backed with mapping metadata.
 	 *
@@ -1331,7 +1325,6 @@ public class QueryMapper {
 			return name;
 		}
 
-
 		@Nullable
 		protected PersistentPropertyPath<MongoPersistentProperty> getPath() {
 			return propertyPath;
@@ -1351,7 +1344,7 @@ public class QueryMapper {
 						PropertyPath.from(Pattern.quote(sourceProperty.getName()), entity.getTypeInformation()));
 			}
 
-			PropertyPath path = toPropertyPath(mongoPath, entity);
+			PropertyPath path = paths.mappedPath(mongoPath, entity.getTypeInformation()).propertyPath();
 
 			if (path == null || isPathToJavaLangClassProperty(path)) {
 				return null;

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/MongoPath.java

@@ -20,10 +20,17 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Objects;
 import java.util.regex.Pattern;
+import java.util.stream.Collectors;
 
 import org.springframework.data.mapping.PropertyPath;
+import org.springframework.data.mongodb.core.mapping.MongoPath.PathSegment.PropertySegment;
+import org.springframework.data.mongodb.core.mapping.MongoPath.RawMongoPath.Keyword;
+import org.springframework.data.util.Lazy;
+import org.springframework.data.util.TypeInformation;
 import org.springframework.lang.NonNull;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ConcurrentLruCache;
 import org.springframework.util.ObjectUtils;
@@ -50,6 +57,128 @@ public sealed interface MongoPath permits MongoPath.RawMongoPath, MongoPath.Mapp
 
 		String segment();
 
+		static PathSegment of(String segment) {
+
+			Keyword keyword = Keyword.mapping.get(segment);
+
+			if (keyword != null) {
+				return new KeywordSegment(keyword, new Segment(segment, false, true));
+			}
+
+			if (PositionSegment.POSITIONAL.matcher(segment).matches()) {
+				return new PositionSegment(new Segment(segment, true, false));
+			}
+
+			if (segment.startsWith("$")) {
+				return new KeywordSegment(null, new Segment(segment, false, true));
+			}
+
+			return new PropertySegment(new Segment(segment, false, false));
+		}
+
+		record Segment(String segment, boolean isNumeric, boolean isKeyword) implements PathSegment {
+
+		}
+
+		class KeywordSegment implements PathSegment {
+
+			final @Nullable Keyword keyword;
+			final Segment segment;
+
+			public KeywordSegment(@Nullable Keyword keyword, Segment segment) {
+
+				this.keyword = keyword;
+				this.segment = segment;
+			}
+
+			@Override
+			public boolean isNumeric() {
+				return false;
+			}
+
+			@Override
+			public boolean isKeyword() {
+				return true;
+			}
+
+			@Override
+			public String segment() {
+				return segment.segment();
+			}
+
+			@Override
+			public String toString() {
+				return segment();
+			}
+		}
+
+		class PositionSegment implements PathSegment {
+
+			/**
+			 * n numeric position <br />
+			 * $[] all positional operator for update operations, <br />
+			 * $[id] filtered positional operator for update operations, <br />
+			 * $ positional operator for update operations, <br />
+			 * $ projection operator when array index position is unknown <br />
+			 */
+			private final static Pattern POSITIONAL = Pattern.compile("\\$\\[[a-zA-Z0-9]*]|\\$|\\d+");
+
+			final Segment segment;
+
+			public PositionSegment(Segment segment) {
+				this.segment = segment;
+			}
+
+			@Override
+			public boolean isNumeric() {
+				return true;
+			}
+
+			@Override
+			public boolean isKeyword() {
+				return false;
+			}
+
+			@Override
+			public String segment() {
+				return segment.segment();
+			}
+
+			@Override
+			public String toString() {
+				return segment();
+			}
+		}
+
+		class PropertySegment implements PathSegment {
+
+			final Segment segment;
+
+			public PropertySegment(Segment segment) {
+				this.segment = segment;
+			}
+
+			@Override
+			public boolean isNumeric() {
+				return false;
+			}
+
+			@Override
+			public boolean isKeyword() {
+				return false;
+			}
+
+			@Override
+			public String segment() {
+				return segment.segment();
+			}
+
+			@Override
+			public String toString() {
+				return segment();
+			}
+		}
+
 	}
 
 	/**
@@ -65,13 +194,13 @@ public sealed interface MongoPath permits MongoPath.RawMongoPath, MongoPath.Mapp
 				RawMongoPath::new);
 
 		private final String path;
-		private final List<Segment> segments;
+		private final List<PathSegment> segments;
 
 		private RawMongoPath(String path) {
 			this(path, segmentsOf(path));
 		}
 
-		RawMongoPath(String path, List<Segment> segments) {
+		RawMongoPath(String path, List<PathSegment> segments) {
 
 			this.path = path;
 			this.segments = List.copyOf(segments);
@@ -89,24 +218,24 @@ public sealed interface MongoPath permits MongoPath.RawMongoPath, MongoPath.Mapp
 			return CACHE.get(path);
 		}
 
-		private static List<Segment> segmentsOf(String path) {
+		private static List<PathSegment> segmentsOf(String path) {
 			return segmentsOf(path.split("\\."));
 		}
 
-		private static List<Segment> segmentsOf(String[] rawSegments) {
+		private static List<PathSegment> segmentsOf(String[] rawSegments) {
 
-			List<Segment> segments = new ArrayList<>(rawSegments.length);
+			List<PathSegment> segments = new ArrayList<>(rawSegments.length);
 			for (String segment : rawSegments) {
-				segments.add(Segment.of(segment));
+				segments.add(PathSegment.of(segment));
 			}
 			return segments;
 		}
 
-		public List<Segment> getSegments() {
+		public List<PathSegment> getSegments() {
 			return this.segments;
 		}
 
-		public List<Segment> segments() {
+		public List<PathSegment> segments() {
 			return this.segments;
 		}
 
@@ -135,55 +264,8 @@ public sealed interface MongoPath permits MongoPath.RawMongoPath, MongoPath.Mapp
 			return StringUtils.collectionToDelimitedString(segments, ".");
 		}
 
-		public record Segment(String segment, boolean keyword, boolean numeric,
-				TargetType targetType) implements PathSegment {
-
-			private final static Pattern POSITIONAL = Pattern.compile("\\$\\[\\d+]");
-
-			static Segment of(String segment) {
-
-				Keyword keyword = Keyword.mapping.get(segment);
+		public enum Keyword {
 
-				if (keyword != null) {
-					return new Segment(segment, true, false, keyword.getType());
-				}
-
-				if (POSITIONAL.matcher(segment).matches()) {
-					return new Segment(segment, true, false, RawMongoPath.Keyword.$POSITIONAL.getType());
-				}
-
-				try {
-					// positional paths
-					Integer.decode(segment);
-					return new Segment(segment, false, true, RawMongoPath.TargetType.PROPERTY);
-				} catch (NumberFormatException e) {
-
-				}
-
-				return new Segment(segment, segment.startsWith("$"), false, RawMongoPath.TargetType.PROPERTY);
-			}
-
-			@Override
-			public String toString() {
-				return segment;
-			}
-
-			@Override
-			public boolean isNumeric() {
-				return numeric;
-			}
-
-			@Override
-			public boolean isKeyword() {
-				return keyword;
-			}
-		}
-
-		enum Keyword {
-
-			$PROJECTION("$", TargetType.PROPERTY), //
-			$POSITIONAL("$[n]", TargetType.PROPERTY), //
-			$ALL_POSITIONAL("$[]", TargetType.PROPERTY), //
 			$IN(TargetType.COLLECTION), //
 			$NIN(TargetType.COLLECTION), //
 			$EXISTS(TargetType.BOOLEAN), //
@@ -249,16 +331,90 @@ public sealed interface MongoPath permits MongoPath.RawMongoPath, MongoPath.Mapp
 	final class MappedMongoPath implements MongoPath {
 
 		private final RawMongoPath source;
-		private final List<MappedSegment> mappedSegments;
+		private final TypeInformation<?> type;
+		private final List<? extends PathSegment> segments;
+		private final Lazy<PropertyPath> propertyPath = Lazy.of(this::assemblePropertyPath);
+		private final Lazy<String> mappedPath = Lazy.of(this::assembleMappedPath);
 
-		public MappedMongoPath(RawMongoPath source, List<MappedSegment> segments) {
+		public MappedMongoPath(RawMongoPath source, TypeInformation<?> type, List<? extends PathSegment> segments) {
 			this.source = source;
-			this.mappedSegments = segments;
+			this.type = type;
+			this.segments = segments;
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (o == this) {
+				return true;
+			}
+			if (o == null || getClass() != o.getClass()) {
+				return false;
+			}
+			MappedMongoPath that = (MappedMongoPath) o;
+			return source.equals(that.source) && type.equals(that.type);
+		}
+
+		@Override
+		public int hashCode() {
+			return Objects.hash(source, type);
+		}
+
+		public static MappedMongoPath just(RawMongoPath source) {
+			return new MappedMongoPath(source, TypeInformation.OBJECT,
+					source.segments().stream().map(it -> new MappedPropertySegment(it.segment(), it, null)).toList());
+		}
+
+		public @Nullable PropertyPath propertyPath() {
+			return this.propertyPath.getNullable();
+		}
+
+		private String assembleMappedPath() {
+			return segments.stream().map(PathSegment::segment).filter(StringUtils::hasText).collect(Collectors.joining("."));
+		}
+
+		private @Nullable PropertyPath assemblePropertyPath() {
+
+			StringBuilder path = new StringBuilder();
+
+			for (PathSegment segment : segments) {
+
+				if (segment instanceof PropertySegment) {
+					return null;
+				}
+
+				if (segment.isKeyword() || segment.isNumeric()) {
+					continue;
+				}
+
+				String name = segment.segment();
+				if (segment instanceof MappedPropertySegment mappedSegment) {
+					name = mappedSegment.getSource().segment();
+				} else if (segment instanceof WrappedSegment wrappedSegment) {
+					if (wrappedSegment.getInner() != null) {
+						name = wrappedSegment.getOuter().getProperty().getName() + "."
+								+ wrappedSegment.getInner().getProperty().getName();
+					} else {
+						name = wrappedSegment.getOuter().getProperty().getName();
+					}
+				}
+
+				if (!path.isEmpty()) {
+					path.append(".");
+				}
+
+				path.append(Pattern.quote(name));
+			}
+
+			if (path.isEmpty()) {
+				return null;
+			}
+
+			return PropertyPath.from(path.toString(), type);
 		}
 
 		@Override
 		public String path() {
-			return StringUtils.collectionToDelimitedString(mappedSegments, ".");
+			return mappedPath.get();
 		}
 
 		public String sourcePath() {
@@ -266,15 +422,76 @@ public sealed interface MongoPath permits MongoPath.RawMongoPath, MongoPath.Mapp
 		}
 
 		@Override
-		public List<MappedSegment> segments() {
-			return mappedSegments;
+		@SuppressWarnings("unchecked")
+		public List<PathSegment> segments() {
+			return (List<PathSegment>) segments;
 		}
 
 		public String toString() {
 			return path();
 		}
 
-		public record MappedSegment(PathSegment source, String mappedName) implements PathSegment {
+		public static class AssociationSegment extends MappedPropertySegment {
+
+			public AssociationSegment(String mappedName, PathSegment source, MongoPersistentProperty property) {
+				super(mappedName, source, property);
+			}
+		}
+
+		public static class WrappedSegment implements PathSegment {
+
+			private final String mappedName;
+			private final MappedPropertySegment outer;
+			private final MappedPropertySegment inner;
+
+			public WrappedSegment(String mappedName, MappedPropertySegment outer, MappedPropertySegment inner) {
+				this.mappedName = mappedName;
+				this.outer = outer;
+				this.inner = inner;
+			}
+
+			public MappedPropertySegment getInner() {
+				return inner;
+			}
+
+			public MappedPropertySegment getOuter() {
+				return outer;
+			}
+
+			@Override
+			public boolean isNumeric() {
+				return false;
+			}
+
+			@Override
+			public boolean isKeyword() {
+				return false;
+			}
+
+			@Override
+			public String segment() {
+				return mappedName;
+			}
+
+			@Override
+			public String toString() {
+				return segment();
+			}
+
+
+		}
+
+		public static class MappedPropertySegment implements PathSegment {
+
+			PathSegment source;
+			String mappedName;
+			MongoPersistentProperty property;
+
+			public MappedPropertySegment(String mappedName, PathSegment source, MongoPersistentProperty property) {
+				this.source = source;
+				this.mappedName = mappedName;
+				this.property = property;
+			}
 
 			@Override
 			public boolean isNumeric() {
@@ -291,11 +508,39 @@ public sealed interface MongoPath permits MongoPath.RawMongoPath, MongoPath.Mapp
 				return mappedName;
 			}
 
+			public boolean isMappedToProperty() {
+				return property != null;
+			}
+
 			@NonNull
 			@Override
 			public String toString() {
 				return mappedName;
 			}
+
+			public PathSegment getSource() {
+				return source;
+			}
+
+			public void setSource(PathSegment source) {
+				this.source = source;
+			}
+
+			public String getMappedName() {
+				return mappedName;
+			}
+
+			public void setMappedName(String mappedName) {
+				this.mappedName = mappedName;
+			}
+
+			public MongoPersistentProperty getProperty() {
+				return property;
+			}
+
+			public void setProperty(MongoPersistentProperty property) {
+				this.property = property;
+			}
 		}
 	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/MongoPaths.java

@@ -19,9 +19,11 @@ import java.util.ArrayList;
 import java.util.List;
 
 import org.springframework.data.mapping.context.MappingContext;
-import org.springframework.data.mongodb.core.mapping.MongoPath.MappedMongoPath.MappedSegment;
-import org.springframework.data.mongodb.core.mapping.MongoPath.RawMongoPath.Segment;
-import org.springframework.data.mongodb.core.mapping.MongoPath.RawMongoPath.TargetType;
+import org.springframework.data.mongodb.core.mapping.MongoPath.MappedMongoPath;
+import org.springframework.data.mongodb.core.mapping.MongoPath.MappedMongoPath.MappedPropertySegment;
+import org.springframework.data.mongodb.core.mapping.MongoPath.MappedMongoPath.WrappedSegment;
+import org.springframework.data.mongodb.core.mapping.MongoPath.PathSegment;
+import org.springframework.data.mongodb.core.mapping.MongoPath.RawMongoPath;
 import org.springframework.data.util.TypeInformation;
 import org.springframework.util.ConcurrentLruCache;
 
@@ -31,7 +33,8 @@ import org.springframework.util.ConcurrentLruCache;
  */
 public class MongoPaths {
 
-	private final ConcurrentLruCache<PathAndType, MongoPath.MappedMongoPath> CACHE = new ConcurrentLruCache<>(128, this::mapFieldNames);
+	private final ConcurrentLruCache<PathAndType, MongoPath.MappedMongoPath> CACHE = new ConcurrentLruCache<>(128,
+			this::mapFieldNames);
 	private final MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext;
 
 	public MongoPaths(MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext) {
@@ -42,15 +45,23 @@ public class MongoPaths {
 		return MongoPath.RawMongoPath.parse(path);
 	}
 
-	public MongoPath mappedPath(MongoPath path, TypeInformation<?> type) {
+	public MappedMongoPath mappedPath(MongoPath path, Class<?> type) {
+		return mappedPath(path, TypeInformation.of(type));
+	}
+
+	public MappedMongoPath mappedPath(MongoPath path, TypeInformation<?> type) {
 
-		if (!(path instanceof MongoPath.RawMongoPath rawMongoPath)) {
-			return path;
+		if (path instanceof MappedMongoPath mappedPath) {
+			return mappedPath;
 		}
 
-		if (!mappingContext.hasPersistentEntityFor(type.getType())) {
-			return path;
+		MongoPath.RawMongoPath rawMongoPath = (RawMongoPath) path;
+
+		MongoPersistentEntity<?> persistentEntity = mappingContext.getPersistentEntity(type);
+		if (persistentEntity == null) {
+			return MappedMongoPath.just(rawMongoPath);
 		}
+
 		return CACHE.get(new PathAndType(rawMongoPath, type));
 	}
 
@@ -60,38 +71,61 @@ public class MongoPaths {
 	MongoPath.MappedMongoPath mapFieldNames(PathAndType cacheKey) {
 
 		MongoPath.RawMongoPath mongoPath = cacheKey.path();
-		MongoPersistentEntity<?> persistentEntity = mappingContext.getPersistentEntity(cacheKey.type());
+		MongoPersistentEntity<?> root = mappingContext.getPersistentEntity(cacheKey.type());
+		MongoPersistentEntity<?> persistentEntity = root;
 
-		List<MappedSegment> segments = new ArrayList<>(mongoPath.getSegments().size());
+		List<PathSegment> segments = new ArrayList<>(mongoPath.getSegments().size());
 
-		for (Segment segment : mongoPath.getSegments()) {
+		for (int i = 0; i < mongoPath.getSegments().size(); i++) {
 
-			if (persistentEntity != null && !segment.keyword()
-					&& (segment.targetType() == TargetType.ANY || segment.targetType() == TargetType.PROPERTY)) {
+			EntityIndexSegment eis = segment(i, mongoPath.getSegments(), persistentEntity);
+			segments.add(eis.segment());
+			persistentEntity = eis.entity();
+			i = eis.index();
+		}
 
-				MongoPersistentProperty persistentProperty = persistentEntity.getPersistentProperty(segment.toString());
+		return new MongoPath.MappedMongoPath(mongoPath, root.getTypeInformation(), segments);
+	}
 
-				String name = segment.segment();
+	EntityIndexSegment segment(int index, List<PathSegment> segments, MongoPersistentEntity<?> currentEntity) {
 
-				if (persistentProperty != null) {
+		PathSegment segment = segments.get(index);
+		MongoPersistentEntity<?> entity = currentEntity;
 
-					if (persistentProperty.isEntity()) {
-						persistentEntity = mappingContext.getPersistentEntity(persistentProperty);
-					}
+		if (entity != null && !segment.isKeyword()) {
 
-					if (persistentProperty.isUnwrapped()) {
-						continue;
-					}
+			MongoPersistentProperty persistentProperty = entity.getPersistentProperty(segment.segment());
+
+			if (persistentProperty != null) {
+
+//				if(persistentProperty.isEntity()) {
+					entity = mappingContext.getPersistentEntity(persistentProperty);
+//				}
 
-					name = persistentProperty.getFieldName();
+				if (persistentProperty.isUnwrapped()) {
+
+					if (segments.size() > index + 1) {
+						EntityIndexSegment inner = segment(index + 1, segments, entity);
+						if (inner.segment() instanceof MappedPropertySegment mappedInnerSegment) {
+							return new EntityIndexSegment(inner.entity(), inner.index(),
+									new WrappedSegment(mappedInnerSegment.getMappedName(),
+											new MappedPropertySegment(persistentProperty.findAnnotation(Unwrapped.class).prefix(), segment,
+													persistentProperty),
+											mappedInnerSegment));
+						}
+					} else {
+						return new EntityIndexSegment(entity, index, new WrappedSegment("", new MappedPropertySegment(
+								persistentProperty.findAnnotation(Unwrapped.class).prefix(), segment, persistentProperty), null));
+					}
 				}
 
-				segments.add(new MappedSegment(segment, name));
-			} else {
-				segments.add(new MappedSegment(segment, segment.segment()));
+				return new EntityIndexSegment(entity, index,
+						new MappedPropertySegment(persistentProperty.getFieldName(), segment, persistentProperty));
 			}
 		}
+		return new EntityIndexSegment(entity, index, segment);
+	}
 
-		return new MongoPath.MappedMongoPath(mongoPath, segments);
+	record EntityIndexSegment(MongoPersistentEntity<?> entity, int index, PathSegment segment) {
 	}
 }

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/mapping/MongoPathsUnitTests.java

@@ -0,0 +1,262 @@
+/*
+ * Copyright 2025-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.mapping;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.data.annotation.Id;
+import org.springframework.data.mapping.PropertyPath;
+import org.springframework.data.mongodb.core.mapping.MongoPath.MappedMongoPath;
+import org.springframework.data.mongodb.core.mapping.MongoPath.MappedMongoPath.MappedPropertySegment;
+import org.springframework.data.mongodb.core.mapping.MongoPath.PathSegment;
+import org.springframework.data.mongodb.core.mapping.MongoPath.PathSegment.PositionSegment;
+import org.springframework.data.mongodb.core.mapping.MongoPath.PathSegment.PropertySegment;
+import org.springframework.data.mongodb.core.mapping.Unwrapped.OnEmpty;
+import org.springframework.data.mongodb.test.util.MongoTestMappingContext;
+
+/**
+ * Unit tests for {@link MongoPaths}
+ * 
+ * @author Christoph Strobl
+ */
+class MongoPathsUnitTests {
+
+	MongoPaths paths;
+	MongoTestMappingContext mappingContext;
+
+	@BeforeEach
+	void beforeEach() {
+
+		mappingContext = MongoTestMappingContext.newTestContext();
+		paths = new MongoPaths(mappingContext);
+	}
+
+	@Test // GH-4516
+	void rawPathCaching() {
+
+		MongoPath sourcePath = paths.create("inner.value.num");
+		MongoPath samePathAgain = paths.create("inner.value.num");
+
+		assertThat(sourcePath).isSameAs(samePathAgain);
+	}
+
+	@Test // GH-4516
+	void mappedPathCaching() {
+
+		MongoPath sourcePath = paths.create("inner.value.num");
+
+		MappedMongoPath mappedPath = paths.mappedPath(sourcePath, Outer.class);
+		MappedMongoPath pathMappedAgain = paths.mappedPath(sourcePath, Outer.class);
+		assertThat(mappedPath).isSameAs(pathMappedAgain) //
+				.isNotEqualTo(paths.mappedPath(sourcePath, Inner.class));
+	}
+
+	@Test // GH-4516
+	void simplePath() {
+
+		MongoPath mongoPath = paths.create("inner.value.num");
+
+		assertThat(mongoPath.segments()).hasOnlyElementsOfType(PathSegment.PropertySegment.class);
+		MappedMongoPath mappedMongoPath = paths.mappedPath(mongoPath, Outer.class);
+
+		assertThat(mappedMongoPath.path()).isEqualTo("inner.val.f_val");
+		assertThat(mappedMongoPath.segments()).hasOnlyElementsOfType(MappedPropertySegment.class);
+		assertThat(mappedMongoPath.propertyPath()).isEqualTo(PropertyPath.from("inner.value.num", Outer.class));
+	}
+
+	@Test // GH-4516
+	void mappedPathWithArrayPosition() {
+
+		MongoPath mongoPath = paths.create("inner.valueList.0.num");
+
+		assertThat(mongoPath.segments()).hasExactlyElementsOfTypes(PropertySegment.class, PropertySegment.class,
+				PositionSegment.class, PropertySegment.class);
+		MappedMongoPath mappedMongoPath = paths.mappedPath(mongoPath, Outer.class);
+
+		assertThat(mappedMongoPath.path()).isEqualTo("inner.valueList.0.f_val");
+		assertThat(mappedMongoPath.segments()).hasExactlyElementsOfTypes(MappedPropertySegment.class,
+				MappedPropertySegment.class, PositionSegment.class, MappedPropertySegment.class);
+		assertThat(mappedMongoPath.propertyPath()).isEqualTo(PropertyPath.from("inner.valueList.num", Outer.class));
+	}
+
+	@Test // GH-4516
+	void mappedPathWithReferenceToNonDomainTypeField() {
+
+		MongoPath mongoPath = paths.create("inner.valueList.0.xxx");
+
+		assertThat(mongoPath.segments()).hasExactlyElementsOfTypes(PropertySegment.class, PropertySegment.class,
+				PositionSegment.class, PropertySegment.class);
+		MappedMongoPath mappedMongoPath = paths.mappedPath(mongoPath, Outer.class);
+
+		assertThat(mappedMongoPath.path()).isEqualTo("inner.valueList.0.xxx");
+		assertThat(mappedMongoPath.segments()).hasExactlyElementsOfTypes(MappedPropertySegment.class,
+				MappedPropertySegment.class, PositionSegment.class, PropertySegment.class);
+		assertThat(mappedMongoPath.propertyPath()).isNull();
+	}
+
+	@Test // GH-4516
+	void mappedPathToPropertyWithinUnwrappedUnwrappedProperty() {
+
+		MongoPath mongoPath = paths.create("inner.wrapper.v1");
+		assertThat(mongoPath.segments()).hasExactlyElementsOfTypes(PropertySegment.class, PropertySegment.class,
+				PropertySegment.class);
+
+		MappedMongoPath mappedMongoPath = paths.mappedPath(mongoPath, Outer.class);
+		assertThat(mappedMongoPath.path()).isEqualTo("inner.pre-fix-v_1");
+
+		assertThat(mappedMongoPath.propertyPath()).isEqualTo(PropertyPath.from("inner.wrapper.v1", Outer.class));
+	}
+
+	@Test // GH-4516
+	void mappedPathToUnwrappedProperty() { // eg. for update mapping
+
+		MongoPath mongoPath = paths.create("inner.wrapper");
+		assertThat(mongoPath.segments()).hasExactlyElementsOfTypes(PropertySegment.class, PropertySegment.class);
+
+		MappedMongoPath mappedMongoPath = paths.mappedPath(mongoPath, Outer.class);
+		assertThat(mappedMongoPath.path()).isEqualTo("inner");
+
+		assertThat(mappedMongoPath.propertyPath()).isEqualTo(PropertyPath.from("inner.wrapper", Outer.class));
+	}
+
+	@Test // GH-4516
+	void justPropertySegments() {
+
+		MongoPath mongoPath = paths.create("inner.value");
+		assertThat(mongoPath.segments()).hasExactlyElementsOfTypes(PropertySegment.class, PropertySegment.class);
+
+		MappedMongoPath mappedMongoPath = paths.mappedPath(mongoPath, Outer.class);
+		assertThat(mappedMongoPath.path()).isEqualTo("inner.val");
+		assertThat(mappedMongoPath.propertyPath()).isEqualTo(PropertyPath.from("inner.value", Outer.class));
+	}
+
+	@Test // GH-4516
+	void withPositionalOperatorForUpdates() {
+
+		MongoPath mongoPath = paths.create("inner.value.$");
+		assertThat(mongoPath.segments()).hasExactlyElementsOfTypes(PropertySegment.class, PropertySegment.class,
+				PositionSegment.class);
+
+		MappedMongoPath mappedMongoPath = paths.mappedPath(mongoPath, Outer.class);
+		assertThat(mappedMongoPath.path()).isEqualTo("inner.val.$");
+		assertThat(mappedMongoPath.propertyPath()).isEqualTo(PropertyPath.from("inner.value", Outer.class));
+	}
+
+	@Test // GH-4516
+	void withProjectionOperatorForArray() {
+
+		MongoPath mongoPath = paths.create("inner.value.$.num");
+		assertThat(mongoPath.segments()).hasExactlyElementsOfTypes(PropertySegment.class, PropertySegment.class,
+				PositionSegment.class, PropertySegment.class);
+
+		MappedMongoPath mappedMongoPath = paths.mappedPath(mongoPath, Outer.class);
+		assertThat(mappedMongoPath.path()).isEqualTo("inner.val.$.f_val");
+		assertThat(mappedMongoPath.propertyPath()).isEqualTo(PropertyPath.from("inner.value.num", Outer.class));
+	}
+
+	@Test // GH-4516
+	void withAllPositionalOperatorForUpdates() {
+
+		MongoPath mongoPath = paths.create("inner.value.$[].num");
+		assertThat(mongoPath.segments()).hasExactlyElementsOfTypes(PropertySegment.class, PropertySegment.class,
+				PositionSegment.class, PropertySegment.class);
+
+		MappedMongoPath mappedMongoPath = paths.mappedPath(mongoPath, Outer.class);
+		assertThat(mappedMongoPath.path()).isEqualTo("inner.val.$[].f_val");
+		assertThat(mappedMongoPath.propertyPath()).isEqualTo(PropertyPath.from("inner.value.num", Outer.class));
+	}
+
+	@Test // GH-4516
+	void withNumericFilteredPositionalOperatorForUpdates() {
+
+		MongoPath mongoPath = paths.create("inner.value.$[1].num");
+		assertThat(mongoPath.segments()).hasExactlyElementsOfTypes(PropertySegment.class, PropertySegment.class,
+				PositionSegment.class, PropertySegment.class);
+
+		MappedMongoPath mappedMongoPath = paths.mappedPath(mongoPath, Outer.class);
+		assertThat(mappedMongoPath.path()).isEqualTo("inner.val.$[1].f_val");
+		assertThat(mappedMongoPath.propertyPath()).isEqualTo(PropertyPath.from("inner.value.num", Outer.class));
+	}
+
+	@Test // GH-4516
+	void withFilteredPositionalOperatorForUpdates() {
+
+		MongoPath mongoPath = paths.create("inner.value.$[elem].num");
+		assertThat(mongoPath.segments()).hasExactlyElementsOfTypes(PropertySegment.class, PropertySegment.class,
+				PositionSegment.class, PropertySegment.class);
+
+		MappedMongoPath mappedMongoPath = paths.mappedPath(mongoPath, Outer.class);
+		assertThat(mappedMongoPath.path()).isEqualTo("inner.val.$[elem].f_val");
+		assertThat(mappedMongoPath.propertyPath()).isEqualTo(PropertyPath.from("inner.value.num", Outer.class));
+	}
+
+	@Test // GH-4516
+	void unwrappedWithNonDomainTypeAndPathThatPointsToPropertyOfUnwrappedType() {
+
+		MongoPath mongoPath = paths.create("inner.wrapper.document.v2");
+		assertThat(mongoPath.segments()).hasExactlyElementsOfTypes(PropertySegment.class, PropertySegment.class,
+				PropertySegment.class, PropertySegment.class);
+
+		MappedMongoPath mappedMongoPath = paths.mappedPath(mongoPath, Outer.class);
+		assertThat(mappedMongoPath.path()).isEqualTo("inner.pre-fix-document.v2");
+		assertThat(mappedMongoPath.propertyPath()).isNull();
+	}
+
+	static class Outer {
+
+		String id;
+		Inner inner;
+
+		@DBRef //
+		Referenced ref;
+
+	}
+
+	static class Inner {
+
+		@Field("val") //
+		Value value;
+
+		@Unwrapped(prefix = "pre-fix-", onEmpty = OnEmpty.USE_NULL) //
+		Wrapper wrapper;
+
+		List<Value> valueList;
+	}
+
+	static class Referenced {
+
+		@Id String id;
+		String value;
+	}
+
+	static class Wrapper {
+
+		@Field("v_1") String v1;
+		String v2;
+		org.bson.Document document;
+	}
+
+	static class Value {
+
+		String s_val;
+
+		@Field("f_val") Float num;
+	}
+}