#384 - Fix return type detection for suspended Kotlin methods.

See DATACMNS-1738 for further reference.

src/main/java/org/springframework/data/r2dbc/repository/query/R2dbcQueryMethod.java

@@ -41,6 +41,7 @@ import org.springframework.data.repository.query.QueryMethod;
 import org.springframework.data.repository.util.ReactiveWrapperConverters;
 import org.springframework.data.repository.util.ReactiveWrappers;
 import org.springframework.data.util.ClassTypeInformation;
+import org.springframework.data.util.Lazy;
 import org.springframework.data.util.TypeInformation;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
@@ -59,10 +60,10 @@ public class R2dbcQueryMethod extends QueryMethod {
 	@SuppressWarnings("rawtypes") //
 	private static final ClassTypeInformation<Slice> SLICE_TYPE = ClassTypeInformation.from(Slice.class);
 
-	private final Method method;
 	private final MappingContext<? extends RelationalPersistentEntity<?>, ? extends RelationalPersistentProperty> mappingContext;
 	private final Optional<Query> query;
 	private final boolean modifying;
+	private final Lazy<Boolean> isCollectionQuery;
 
 	private @Nullable RelationalEntityMetadata<?> metadata;
 
@@ -110,10 +111,11 @@ public class R2dbcQueryMethod extends QueryMethod {
 			}
 		}
 
-		this.method = method;
 		this.query = Optional.ofNullable(
 				AnnotatedElementUtils.findMergedAnnotation(method, Query.class));
 		this.modifying = AnnotatedElementUtils.hasAnnotation(method, Modifying.class);
+		this.isCollectionQuery = Lazy.of(() -> !(isPageQuery() || isSliceQuery())
+				&& ReactiveWrappers.isMultiValueType(metadata.getReturnType(method).getType()));
 	}
 
 	/* (non-Javadoc)
@@ -129,7 +131,7 @@ public class R2dbcQueryMethod extends QueryMethod {
 	 */
 	@Override
 	public boolean isCollectionQuery() {
-		return !(isPageQuery() || isSliceQuery()) && ReactiveWrappers.isMultiValueType(method.getReturnType());
+		return isCollectionQuery.get();
 	}
 
 	/* (non-Javadoc)

src/test/kotlin/org/springframework/data/r2dbc/repository/query/ReactiveR2dbcQueryMethodCoroutineUnitTests.kt

@@ -0,0 +1,62 @@
+/*
+ * 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.r2dbc.repository.query
+
+import kotlinx.coroutines.flow.Flow
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.springframework.data.projection.SpelAwareProxyProjectionFactory
+import org.springframework.data.r2dbc.mapping.R2dbcMappingContext
+import org.springframework.data.repository.core.support.DefaultRepositoryMetadata
+import org.springframework.data.repository.kotlin.CoroutineCrudRepository
+import kotlin.coroutines.Continuation
+
+/**
+ * Unit tests for [R2dbcQueryMethod] using Coroutine repositories.
+ *
+ * @author Mark Paluch
+ */
+class ReactiveR2dbcQueryMethodCoroutineUnitTests {
+
+	val projectionFactory = SpelAwareProxyProjectionFactory()
+
+	data class Person(val id: String)
+
+	interface PersonRepository : CoroutineCrudRepository<Person, String> {
+
+		suspend fun findSuspendAllById(): Flow<Person>
+
+		fun findAllById(): Flow<Person>
+	}
+
+	@Test // gh-384
+	internal fun `should consider methods returning Flow as collection queries`() {
+
+		val method = PersonRepository::class.java.getMethod("findAllById")
+		val queryMethod = R2dbcQueryMethod(method, DefaultRepositoryMetadata(PersonRepository::class.java), projectionFactory, R2dbcMappingContext())
+
+		assertThat(queryMethod.isCollectionQuery).isTrue()
+	}
+
+	@Test // gh-384
+	internal fun `should consider suspended methods returning Flow as collection queries`() {
+
+		val method = PersonRepository::class.java.getMethod("findSuspendAllById", Continuation::class.java)
+		val queryMethod = R2dbcQueryMethod(method, DefaultRepositoryMetadata(PersonRepository::class.java), projectionFactory, R2dbcMappingContext())
+
+		assertThat(queryMethod.isCollectionQuery).isTrue()
+	}
+}