DATAMONGO-2596 - Polishing.

Refactor KPropertyPath.toString() into KProperty.asPath() extension function to allow rendering simple properties and property paths into a String property path.

Original pull request: #880.

spring-data-mongodb/src/main/kotlin/org/springframework/data/mongodb/core/query/KPropertyPath.kt

@@ -20,6 +20,7 @@ import kotlin.reflect.KProperty1
 
 /**
  * Abstraction of a property path consisting of [KProperty].
+ *
  * @author Tjeu Kayim
  * @author Mark Paluch
  * @author Yoann de Martino
@@ -28,11 +29,7 @@ import kotlin.reflect.KProperty1
 class KPropertyPath<T, U>(
 		internal val parent: KProperty<U>,
 		internal val child: KProperty1<U, T>
-) : KProperty<T> by child {
-	override fun toString(): String {
-		return asString(this)
-	}
-}
+) : KProperty<T> by child
 
 /**
  * Recursively construct field name for a nested property.

spring-data-mongodb/src/main/kotlin/org/springframework/data/mongodb/core/query/KPropertyPathExtensions.kt

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2020 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.query
+
+import kotlin.reflect.KProperty
+
+/**
+ * Extension for [KProperty] providing an `toPath` function to render a [KProperty] as property path.
+ *
+ * @author Mark Paluch
+ * @since 3.1
+ */
+fun KProperty<*>.toPath(): String = asString(this)

spring-data-mongodb/src/test/kotlin/org/springframework/data/mongodb/core/query/KPropertyPathTests.kt

@@ -19,8 +19,11 @@ import org.assertj.core.api.Assertions.assertThat
 import org.junit.Test
 
 /**
+ * Unit tests for [KPropertyPath] and its extensions.
+ *
  * @author Tjeu Kayim
  * @author Yoann de Martino
+ * @author Mark Paluch
  */
 class KPropertyPathTests {
 
@@ -62,21 +65,30 @@ class KPropertyPathTests {
 	}
 
 	@Test
-	fun `Convert nested KProperty to field name using toString()`() {
+	fun `Convert simple KProperty to property path using toPath`() {
 
-		val property = (Book::author / Author::name).toString()
+		class AnotherEntity(val entity: String)
+
+		val property = (AnotherEntity::entity).toPath()
+
+		assertThat(property).isEqualTo("entity")
+	}
+
+	@Test
+	fun `Convert nested KProperty to field name using toPath()`() {
+
+		val property = (Book::author / Author::name).toPath()
 
 		assertThat(property).isEqualTo("author.name")
 	}
 
-
 	@Test
-	fun `Convert triple nested KProperty to field name using toString()`() {
+	fun `Convert triple nested KProperty to property path using toPath`() {
 
 		class Entity(val book: Book)
 		class AnotherEntity(val entity: Entity)
 
-		val property = (AnotherEntity::entity / Entity::book / Book::author / Author::name).toString()
+		val property = (AnotherEntity::entity / Entity::book / Book::author / Author::name).toPath()
 
 		assertThat(property).isEqualTo("entity.book.author.name")
 	}

src/main/asciidoc/new-features.adoc

@@ -7,6 +7,7 @@
 * <<mongo.auditing,Reactive auditing>> enabled through `@EnableReactiveMongoAuditing`. `@EnableMongoAuditing` no longer registers `ReactiveAuditingEntityCallback`.
 * Reactive SpEL support in `@Query` and `@Aggregation` query methods.
 * Aggregation hints via `AggregationOptions.builder().hint(bson).build()`.
+* Extension Function `KProperty.asPath()` to render property references into a property path representation.
 
 [[new-features.3.0]]
 == What's New in Spring Data MongoDB 3.0