IndexOutOfBoundsException when using FastAdapterDiffUtil on expandable list

[michalbujalski]

About this issue

I'm using FastAdapterDiffUtil to update current list of items. The adapter which uses ExpandableExtension and has withIsExpanded set before putting into DiffUtil
Nothing new when updating the list:
FastAdapterDiffUtil.set( expandableAdapter.getItemAdapter(), items, new ExpandedDiffCallback(), false );
Also I need to manually control expanded items state so my ISubItem has isAutoExpanding set to false

Stacktrace:
java.lang.IndexOutOfBoundsException: Index: 2, Size: 2 at java.util.ArrayList.get(ArrayList.java:437) at com.mikepenz.fastadapter.utils.DefaultItemListImpl.get(DefaultItemListImpl.java:29) at com.mikepenz.fastadapter.utils.DefaultItemListImpl.get(DefaultItemListImpl.java:15) at com.mikepenz.fastadapter.adapters.ModelAdapter.getAdapterItem(ModelAdapter.java:265) at com.mikepenz.fastadapter.FastAdapter.getItem(FastAdapter.java:856) at com.mikepenz.fastadapter.expandable.ExpandableExtension.notifyAdapterItemRangeChanged(ExpandableExtension.java:154) at com.mikepenz.fastadapter.FastAdapter.notifyAdapterItemRangeChanged(FastAdapter.java:1364) at com.mikepenz.fastadapter.commons.utils.FastAdapterDiffUtil$FastAdapterListUpdateCallback.onChanged(FastAdapterDiffUtil.java:191) at android.support.v7.util.BatchingListUpdateCallback.dispatchLastEvent(BatchingListUpdateCallback.java:65) at android.support.v7.util.BatchingListUpdateCallback.onRemoved(BatchingListUpdateCallback.java:94) at android.support.v7.util.DiffUtil$DiffResult.dispatchRemovals(DiffUtil.java:791) at android.support.v7.util.DiffUtil$DiffResult.dispatchUpdatesTo(DiffUtil.java:713) at com.mikepenz.fastadapter.commons.utils.FastAdapterDiffUtil.set(FastAdapterDiffUtil.java:57) at com.mikepenz.fastadapter.commons.utils.FastAdapterDiffUtil.set(FastAdapterDiffUtil.java:75)

Steps to reproduce:

List with two expandable items everyone of each has one child
Expand the first parent. Update the list with new items.

Calling collapse before FastAdapterDiffUtil.set solves the problem. Checked out previous implementation and noticed that in v 2.x callapse was caled at the beginning (before calculating diff result). Is this a bug? Is there a build-in way to persist expandable state after using diff utils ?

Details

• [ 3.2.2@aar] Used library version
• [27.0.2 ] Used support library version
• [26.0.2 ] Used gradle build tools version
• [3.0.1] Used tooling / Android Studio version
• [] Other used libraries, potential conflicting libraries

Checklist

• Searched for similar issues
• Checked out the sample application
• Read the README
• Checked out the CHANGELOG
• Checked out the MIGRATION GUIDE

[mikepenz]

@michalbujalski sorry the FastAdapterDiffUtil can not handle expendables. if they are expanded.

I think you are right that we require a collapse before that again. as I don't think there is a nice solution to maintain the current open state. (other than collapsing, remembering, restoring it.