Fix query execution mode detection for aggregate types that implement Streamable.

We now short-circuit the QueryMethod.isCollectionQuery() algorithm in case we find the concrete domain type or any subclass of it.

Fixes #2869.

src/main/java/org/springframework/data/repository/core/support/AbstractRepositoryMetadata.java

@@ -96,12 +96,13 @@ public abstract class AbstractRepositoryMetadata implements RepositoryMetadata {
 		return returnType;
 	}
 
+	@Override
 	public Class<?> getReturnedDomainClass(Method method) {
 
 		TypeInformation<?> returnType = getReturnType(method);
+		returnType = ReactiveWrapperConverters.unwrapWrapperTypes(returnType);
 
-		return QueryExecutionConverters.unwrapWrapperTypes(ReactiveWrapperConverters.unwrapWrapperTypes(returnType))
-				.getType();
+		return QueryExecutionConverters.unwrapWrapperTypes(returnType, getDomainTypeInformation()).getType();
 	}
 
 	public Class<?> getRepositoryInterface() {

src/main/java/org/springframework/data/repository/query/QueryMethod.java

@@ -24,16 +24,17 @@ import java.util.stream.Stream;
 
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
-import org.springframework.data.domain.Window;
 import org.springframework.data.domain.ScrollPosition;
 import org.springframework.data.domain.Slice;
 import org.springframework.data.domain.Sort;
+import org.springframework.data.domain.Window;
 import org.springframework.data.projection.ProjectionFactory;
 import org.springframework.data.repository.core.EntityMetadata;
 import org.springframework.data.repository.core.RepositoryMetadata;
 import org.springframework.data.repository.util.QueryExecutionConverters;
 import org.springframework.data.repository.util.ReactiveWrapperConverters;
 import org.springframework.data.util.Lazy;
+import org.springframework.data.util.NullableWrapperConverters;
 import org.springframework.data.util.ReactiveWrappers;
 import org.springframework.data.util.TypeInformation;
 import org.springframework.util.Assert;
@@ -296,7 +297,15 @@ public class QueryMethod {
 			return false;
 		}
 
-		Class<?> returnType = metadata.getReturnType(method).getType();
+		TypeInformation<?> returnTypeInformation = metadata.getReturnType(method);
+
+		// Check against simple wrapper types first
+		if (metadata.getDomainTypeInformation()
+				.isAssignableFrom(NullableWrapperConverters.unwrapActualType(returnTypeInformation))) {
+			return false;
+		}
+
+		Class<?> returnType = returnTypeInformation.getType();
 
 		if (QueryExecutionConverters.supports(returnType) && !QueryExecutionConverters.isSingleValue(returnType)) {
 			return true;

src/main/java/org/springframework/data/repository/util/QueryExecutionConverters.java

@@ -36,8 +36,8 @@ import org.springframework.core.convert.converter.GenericConverter;
 import org.springframework.core.convert.support.ConfigurableConversionService;
 import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.data.domain.Page;
-import org.springframework.data.domain.Window;
 import org.springframework.data.domain.Slice;
+import org.springframework.data.domain.Window;
 import org.springframework.data.geo.GeoResults;
 import org.springframework.data.util.CustomCollections;
 import org.springframework.data.util.NullableWrapper;
@@ -85,6 +85,7 @@ public abstract class QueryExecutionConverters {
 	private static final Set<Class<?>> ALLOWED_PAGEABLE_TYPES = new HashSet<>();
 	private static final Map<Class<?>, ExecutionAdapter> EXECUTION_ADAPTER = new HashMap<>();
 	private static final Map<Class<?>, Boolean> supportsCache = new ConcurrentReferenceHashMap<>();
+	private static final TypeInformation<Void> VOID_INFORMATION = TypeInformation.of(Void.class);
 
 	static {
 
@@ -235,15 +236,21 @@ public abstract class QueryExecutionConverters {
 	}
 
 	/**
-	 * Recursively unwraps well known wrapper types from the given {@link TypeInformation}.
+	 * Recursively unwraps well known wrapper types from the given {@link TypeInformation} but aborts at the given
+	 * reference type.
 	 *
 	 * @param type must not be {@literal null}.
+	 * @param reference must not be {@literal null}.
 	 * @return will never be {@literal null}.
 	 */
-	public static TypeInformation<?> unwrapWrapperTypes(TypeInformation<?> type) {
+	public static TypeInformation<?> unwrapWrapperTypes(TypeInformation<?> type, TypeInformation<?> reference) {
 
 		Assert.notNull(type, "type must not be null");
 
+		if (reference.isAssignableFrom(type)) {
+			return type;
+		}
+
 		Class<?> rawType = type.getType();
 
 		boolean needToUnwrap = type.isCollectionLike() //
@@ -253,7 +260,17 @@ public abstract class QueryExecutionConverters {
 				|| supports(rawType) //
 				|| Stream.class.isAssignableFrom(rawType);
 
-		return needToUnwrap ? unwrapWrapperTypes(type.getRequiredComponentType()) : type;
+		return needToUnwrap ? unwrapWrapperTypes(type.getRequiredComponentType(), reference) : type;
+	}
+
+	/**
+	 * Recursively unwraps well known wrapper types from the given {@link TypeInformation}.
+	 *
+	 * @param type must not be {@literal null}.
+	 * @return will never be {@literal null}.
+	 */
+	public static TypeInformation<?> unwrapWrapperTypes(TypeInformation<?> type) {
+		return unwrapWrapperTypes(type, VOID_INFORMATION);
 	}
 
 	/**