DataBinder throws IndexOutOfBoundsException when indexed parameter uses nonconsecutive indices

[cbartolome]

This test fails when added to DataBinderConstructTests.java:

	@Test
	void listBindingWithNonconsecutiveIndices() {
		MapValueResolver valueResolver = new MapValueResolver(Map.of(
				"dataClassList[0].param1", "value1", "dataClassList[0].param2", "true",
				"dataClassList[1].param1", "value2", "dataClassList[1].param2", "true",
				"dataClassList[3].param1", "value3", "dataClassList[3].param2", "true"));

		DataBinder binder = initDataBinder(ListDataClass.class);
		binder.construct(valueResolver);

		ListDataClass dataClass = getTarget(binder);
		List<DataClass> list = dataClass.dataClassList();

		assertThat(list.get(0).param1()).isEqualTo("value1");
		assertThat(list.get(1).param1()).isEqualTo("value2");
		assertThat(list.get(3).param1()).isEqualTo("value3");
	}

The stack trace looks like this:

Index 3 out of bounds for length 3
java.lang.IndexOutOfBoundsException: Index 3 out of bounds for length 3
	at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
	at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
	at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:266)
	at java.base/java.util.Objects.checkIndex(Objects.java:361)
	at java.base/java.util.ArrayList.set(ArrayList.java:441)
	at org.springframework.validation.DataBinder.createList(DataBinder.java:1039)
	at org.springframework.validation.DataBinder.createObject(DataBinder.java:936)
	at org.springframework.validation.DataBinder.construct(DataBinder.java:885)
	at org.springframework.validation.DataBinderConstructTests.listBindingWithNonconsecutiveIndices(DataBinderConstructTests.java:132)
	at java.base/java.lang.reflect.Method.invoke(Method.java:569)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)

I think the problem is with this line in DataBinder.createList():

indexes.forEach(i -> list.add(null));

In order to support nonconsecutive indices, it would need to create enough elements to match the value of highest index, but it's instead creating enough elements to match the count of indices that were submitted.

[rstoyanchev]

Thanks for the analysis and test. Yes, we should be going by the calculated size rather than the number of indexes.