DATAMONGO-2417 - Typesafe Kotlin Extension for distinct queries.

We now provide extensions for imperative and reactive distinct queries accepting Kotlin's KProperty and KProperty1 to express type-safe queries:

mongo.query<Customer>().distinct(Customer::name)

mongo.distinct(Customer::name)

Original Pull Request: #809

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

@@ -15,7 +15,10 @@
  */
 package org.springframework.data.mongodb.core
 
+import org.springframework.data.mongodb.core.query.asString
 import kotlin.reflect.KClass
+import kotlin.reflect.KProperty
+import kotlin.reflect.KProperty1
 
 /**
  * Extension for [ExecutableFindOperation.query] providing a [KClass] based variant.
@@ -38,6 +41,15 @@ fun <T : Any> ExecutableFindOperation.query(entityClass: KClass<T>): ExecutableF
 inline fun <reified T : Any> ExecutableFindOperation.query(): ExecutableFindOperation.ExecutableFind<T> =
 		query(T::class.java)
 
+/**
+ * Extension for [ExecutableFindOperation.query] for a type-safe projection of distinct values.
+ *
+ * @author Mark Paluch
+ * @since 2.3
+ */
+inline fun <reified T : Any> ExecutableFindOperation.distinct(field : KProperty1<T, *>): ExecutableFindOperation.TerminatingDistinct<Any> =
+		query(T::class.java).distinct(field.name)
+
 /**
  * Extension for [ExecutableFindOperation.FindWithProjection.as] providing a [KClass] based variant.
  *
@@ -78,3 +90,12 @@ fun <T : Any> ExecutableFindOperation.DistinctWithProjection.asType(resultType:
  */
 inline fun <reified T : Any> ExecutableFindOperation.DistinctWithProjection.asType(): ExecutableFindOperation.TerminatingDistinct<T> =
 		`as`(T::class.java)
+
+/**
+ * Extension for [ExecutableFindOperation.FindDistinct.distinct] leveraging KProperty.
+ *
+ * @author Mark Paluch
+ * @since 2.3
+ */
+fun ExecutableFindOperation.FindDistinct.distinct(key: KProperty<*>): ExecutableFindOperation.TerminatingDistinct<Any> =
+		distinct(asString(key))

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

@@ -20,7 +20,10 @@ import kotlinx.coroutines.reactive.asFlow
 import kotlinx.coroutines.reactive.awaitFirstOrNull
 import kotlinx.coroutines.reactive.awaitSingle
 import org.springframework.data.geo.GeoResult
+import org.springframework.data.mongodb.core.query.asString
 import kotlin.reflect.KClass
+import kotlin.reflect.KProperty
+import kotlin.reflect.KProperty1
 
 /**
  * Extension for [ReactiveFindOperation.query] providing a [KClass] based variant.
@@ -41,6 +44,15 @@ fun <T : Any> ReactiveFindOperation.query(entityClass: KClass<T>): ReactiveFindO
 inline fun <reified T : Any> ReactiveFindOperation.query(): ReactiveFindOperation.ReactiveFind<T> =
 		query(T::class.java)
 
+/**
+ * Extension for [ReactiveFindOperation.query] for a type-safe projection of distinct values.
+ *
+ * @author Mark Paluch
+ * @since 2.3
+ */
+inline fun <reified T : Any> ReactiveFindOperation.distinct(field : KProperty1<T, *>): ReactiveFindOperation.TerminatingDistinct<Any> =
+		query(T::class.java).distinct(field.name)
+
 /**
  * Extension for [ReactiveFindOperation.FindWithProjection.as] providing a [KClass] based variant.
  *
@@ -79,6 +91,15 @@ fun <T : Any> ReactiveFindOperation.DistinctWithProjection.asType(resultType: KC
 inline fun <reified T : Any> ReactiveFindOperation.DistinctWithProjection.asType(): ReactiveFindOperation.TerminatingDistinct<T> =
 		`as`(T::class.java)
 
+/**
+ * Extension for [ReactiveFindOperation.FindDistinct.distinct] leveraging KProperty.
+ *
+ * @author Mark Paluch
+ * @since 2.3
+ */
+fun ReactiveFindOperation.FindDistinct.distinct(key: KProperty<*>): ReactiveFindOperation.TerminatingDistinct<Any> =
+		distinct(asString(key))
+
 /**
  * Non-nullable Coroutines variant of [ReactiveFindOperation.TerminatingFind.one].
  *

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

@@ -16,6 +16,7 @@
 package org.springframework.data.mongodb.core
 
 import example.first.First
+import io.mockk.every
 import io.mockk.mockk
 import io.mockk.verify
 import org.junit.Test
@@ -32,6 +33,10 @@ class ExecutableFindOperationExtensionsTests {
 
 	val distinctWithProjection = mockk<ExecutableFindOperation.DistinctWithProjection>(relaxed = true)
 
+	val findDistinct = mockk<ExecutableFindOperation.FindDistinct>(relaxed = true)
+
+	val executableFind = mockk<ExecutableFindOperation.ExecutableFind<KotlinUser>>(relaxed = true)
+
 	@Test // DATAMONGO-1689
 	@Suppress("DEPRECATION")
 	fun `ExecutableFindOperation#query(KClass) extension should call its Java counterpart`() {
@@ -76,4 +81,25 @@ class ExecutableFindOperationExtensionsTests {
 		distinctWithProjection.asType<User>()
 		verify { distinctWithProjection.`as`(User::class.java) }
 	}
+
+	@Test // DATAMONGO-2417
+	fun `ExecutableFindOperation#distrinct() using KProperty1 should call its Java counterpart`() {
+
+		every { operation.query(KotlinUser::class.java) } returns executableFind
+
+		operation.distinct(KotlinUser::username)
+		verify {
+			operation.query(KotlinUser::class.java)
+			executableFind.distinct("username")
+		}
+	}
+
+	@Test // DATAMONGO-2417
+	fun `ExecutableFindOperation#FindDistinct#field() using KProperty should call its Java counterpart`() {
+
+		findDistinct.distinct(KotlinUser::username)
+		verify { findDistinct.distinct("username") }
+	}
+
+	data class KotlinUser(val username: String)
 }

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

@@ -42,6 +42,10 @@ class ReactiveFindOperationExtensionsTests {
 
 	val distinctWithProjection = mockk<ReactiveFindOperation.DistinctWithProjection>(relaxed = true)
 
+	val findDistinct = mockk<ReactiveFindOperation.FindDistinct>(relaxed = true)
+
+	val reactiveFind = mockk<ReactiveFindOperation.ReactiveFind<KotlinUser>>(relaxed = true)
+
 	@Test // DATAMONGO-1719
 	@Suppress("DEPRECATION")
 	fun `ReactiveFind#query(KClass) extension should call its Java counterpart`() {
@@ -87,6 +91,25 @@ class ReactiveFindOperationExtensionsTests {
 		verify { distinctWithProjection.`as`(User::class.java) }
 	}
 
+	@Test // DATAMONGO-2417
+	fun `ReactiveFind#distrinct() using KProperty1 should call its Java counterpart`() {
+
+		every { operation.query(KotlinUser::class.java) } returns reactiveFind
+
+		operation.distinct(KotlinUser::username)
+		verify {
+			operation.query(KotlinUser::class.java)
+			reactiveFind.distinct("username")
+		}
+	}
+
+	@Test // DATAMONGO-2417
+	fun `ReactiveFind#FindDistinct#field() using KProperty should call its Java counterpart`() {
+
+		findDistinct.distinct(KotlinUser::username)
+		verify { findDistinct.distinct("username") }
+	}
+
 	@Test // DATAMONGO-2209
 	fun terminatingFindAwaitOneWithValue() {
 
@@ -299,4 +322,6 @@ class ReactiveFindOperationExtensionsTests {
 			spec.all()
 		}
 	}
+
+	data class KotlinUser(val username: String)
 }