DATACMNS-1484 - Fixed too aggressive conversion to Streamable in IterableToStreamableConverter.

We now explicitly check for the target type to be assignable to Streamable to opt into conversion. Without that check, every collection returned from a method declaring Iterable as return type would've been converted into a Streamable by accident.

Related ticket: DATACMNS-1430.

Author: odrotbohm

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

@@ -699,6 +699,10 @@ public Set<ConvertiblePair> getConvertibleTypes() {
 		@Override
 		public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
 
+			if (sourceType.isAssignableTo(targetType)) {
+				return false;
+			}
+
 			if (!Iterable.class.isAssignableFrom(sourceType.getType())) {
 				return false;
 			}

src/test/java/org/springframework/data/repository/util/QueryExecutionConvertersUnitTests.java

@@ -355,6 +355,15 @@ public void convertsToStreamableWrapperImplementingStreamable() throws Exception
 				.containsExactly("foo");
 	}
 
+	@Test // DATACMNS-1484
+	public void doesNotConvertCollectionToStreamableIfReturnTypeIsIterable() {
+
+		List<String> source = Arrays.asList("1", "2");
+
+		assertThat(conversionService.convert(source, Iterable.class)).isSameAs(source);
+
+	}
+
 	interface Sample {
 
 		Page<String> pages();