Polishing.

Update tests to make use of ValueSource.
Replace regex based path inspection with segment by segment analysis.

Original Pull Request: #4427

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

@@ -1089,7 +1089,7 @@ public class QueryMapper {
 	protected static class MetadataBackedField extends Field {
 
 		private static final Pattern POSITIONAL_PARAMETER_PATTERN = Pattern.compile("\\.\\$(\\[.*?\\])?");
-		private static final Pattern DOT_POSITIONAL_PATTERN = Pattern.compile("\\.\\d+(?!$)");
+		private static final Pattern NUMERIC_SEGMENT = Pattern.compile("\\d+");
 		private static final String INVALID_ASSOCIATION_REFERENCE = "Invalid path reference %s; Associations can only be pointed to directly or via their id property";
 
 		private final MongoPersistentEntity<?> entity;
@@ -1231,26 +1231,13 @@ public class QueryMapper {
 		private PersistentPropertyPath<MongoPersistentProperty> getPath(String pathExpression,
 				@Nullable MongoPersistentProperty sourceProperty) {
 
-			String rawPath = removePlaceholders(POSITIONAL_OPERATOR,
-					removePlaceholders(DOT_POSITIONAL_PATTERN, pathExpression));
-            // fix xx.11.22.33 becomes xx3, it should be xx.33, then path should be null. (test mapNestedLastBigIntegerFieldCorrectly)
-            if (pathExpression.contains(".")) {
-                String lastDotString = pathExpression.substring(pathExpression.lastIndexOf("."));
-                int lastDotLength = lastDotString.length();
-                int newLength = 0;
-                if (rawPath.contains(".")) {
-                    newLength = rawPath.substring(rawPath.lastIndexOf(".")).length();
-                }
-                if (lastDotLength != newLength) {
-                    rawPath = rawPath.substring(0, rawPath.length() - 1) + lastDotString;
-                }
-            }
-
 			if (sourceProperty != null && sourceProperty.getOwner().equals(entity)) {
 				return mappingContext.getPersistentPropertyPath(
 						PropertyPath.from(Pattern.quote(sourceProperty.getName()), entity.getTypeInformation()));
 			}
 
+			String rawPath = resolvePath(pathExpression);
+
 			PropertyPath path = forName(rawPath);
 			if (path == null || isPathToJavaLangClassProperty(path)) {
 				return null;
@@ -1345,6 +1332,38 @@ public class QueryMapper {
 			return false;
 		}
 
+		private static String resolvePath(String source) {
+
+			String[] segments = source.split("\\.");
+			if (segments.length == 1) {
+				return source;
+			}
+
+			List<String> path = new ArrayList<>(segments.length);
+
+			/* always start from a property, so we can skip the first segment.
+			   from there remove any position placeholder */
+			for(int i=1; i < segments.length; i++) {
+				String segment = segments[i];
+				if (segment.startsWith("[") && segment.endsWith("]")) {
+					continue;
+				}
+				if (NUMERIC_SEGMENT.matcher(segment).matches()) {
+					continue;
+				}
+				path.add(segment);
+			}
+
+			// when property is followed only by placeholders eg. 'values.0.3.90'
+			// or when there is no difference in the number of segments
+			if (path.isEmpty() || segments.length == path.size() + 1) {
+				return source;
+			}
+
+			path.add(0, segments[0]);
+			return StringUtils.collectionToDelimitedString(path, ".");
+		}
+
 		/**
 		 * Return the {@link Converter} to be used to created the mapped key. Default implementation will use
 		 * {@link PropertyToFieldNameConverter}.

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/UpdateMapperUnitTests.java

@@ -35,6 +35,8 @@ import org.bson.types.ObjectId;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 import org.mockito.Mockito;
 import org.mockito.junit.jupiter.MockitoExtension;
 import org.springframework.core.convert.converter.Converter;
@@ -1213,34 +1215,26 @@ class UpdateMapperUnitTests {
 		assertThat(mappedUpdate).isEqualTo(new org.bson.Document("$set", new org.bson.Document("levelOne.a.b.d", "e")));
 	}
 
-	@Test // GH-3775
-	void mapNestedIntegerFieldCorrectly() {
+	@ParameterizedTest // GH-3775, GH-4426
+	@ValueSource(strings = {"levelOne.0.1.3", "levelOne.0.1.32", "levelOne2.0.1.32", "levelOne2.0.1.320"})
+	void mapNestedIntegerFieldCorrectly(String path) {
 
-		Update update = new Update().set("levelOne.0.1.3", "4");
+		Update update = new Update().set(path, "4");
 		Document mappedUpdate = mapper.getMappedObject(update.getUpdateObject(),
 				context.getPersistentEntity(EntityWithNestedMap.class));
 
-		assertThat(mappedUpdate).isEqualTo(new org.bson.Document("$set", new org.bson.Document("levelOne.0.1.3", "4")));
+		assertThat(mappedUpdate).isEqualTo(new org.bson.Document("$set", new org.bson.Document(path, "4")));
 	}
 
-    @Test
-    void mapNestedLastBigIntegerFieldCorrectly() {
-
-        Update update = new Update().set("levelOne.0.1.32", "4");
-        Document mappedUpdate = mapper.getMappedObject(update.getUpdateObject(),
-            context.getPersistentEntity(EntityWithNestedMap.class));
-
-        assertThat(mappedUpdate).isEqualTo(new org.bson.Document("$set", new org.bson.Document("levelOne.0.1.32", "4")));
-    }
-
-	@Test // GH-3775
-	void mapNestedMixedStringIntegerFieldCorrectly() {
+	@ParameterizedTest // GH-3775, GH-4426
+	@ValueSource(strings = {"levelOne.0.1.c", "levelOne.0.1.c.32", "levelOne2.0.1.32.c", "levelOne2.0.1.c.320"})
+	void mapNestedMixedStringIntegerFieldCorrectly(String path) {
 
-		Update update = new Update().set("levelOne.0.1.c", "4");
+		Update update = new Update().set(path, "4");
 		Document mappedUpdate = mapper.getMappedObject(update.getUpdateObject(),
 				context.getPersistentEntity(EntityWithNestedMap.class));
 
-		assertThat(mappedUpdate).isEqualTo(new org.bson.Document("$set", new org.bson.Document("levelOne.0.1.c", "4")));
+		assertThat(mappedUpdate).isEqualTo(new org.bson.Document("$set", new org.bson.Document(path, "4")));
 	}
 
 	@Test // GH-3775
@@ -1730,7 +1724,6 @@ class UpdateMapperUnitTests {
 
 	static class EntityWithNestedMap {
 		Map<String, Map<String, Map<String, Object>>> levelOne;
-        // for test mapNestedLastBigIntegerFieldCorrectly()
 		Map<String, Map<String, Map<String, Object>>> levelOne2;
 	}