Using stable IDs in TabsAdapter crashes when deleting first tab

[jonalmeida]

Add the following the TabsAdapter in browser-tabstray:

init {
    setHasStableIds(true)
}

override fun getItemId(position: Int): Long {
    return position.toLong()
}

2021-03-26 13:32:52.044 32127-32127/org.mozilla.samples.browser E/ExceptionHandler: Uncaught exception handled: 
    java.lang.IndexOutOfBoundsException: Inconsistency detected. Invalid item position 0(offset:-1).state:3 androidx.recyclerview.widget.RecyclerView{2902363 VFED..... ......ID 0,154-1080,2050 #7f09021a app:id/tabsTray}, adapter:mozilla.components.browser.tabstray.TabsAdapter@e038680, layout:androidx.recyclerview.widget.GridLayoutManager@17b74b9, context:org.mozilla.samples.browser.BrowserActivity@2b2f2c1
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6183)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6118)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6114)
        at androidx.recyclerview.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2303)
        at androidx.recyclerview.widget.GridLayoutManager.layoutChunk(GridLayoutManager.java:561)
        at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1587)
        at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:675)
        at androidx.recyclerview.widget.GridLayoutManager.onLayoutChildren(GridLayoutManager.java:170)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep1(RecyclerView.java:4085)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:3849)
        at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4404)

┆Issue is synchronized with this Jira Task

[jonalmeida]

We know that adding stable IDs and getItemId for multi-select is needed and indeed correct as we can see it in the demo sunflower app as well.

[jonalmeida]

Paired on this with @eliserichards and went through the TabsPresenter code to verify we were doing everything right (we were).

The issue turned out to be our reliance on the sunflower app's implementation of getItemId:

override fun getItemId(position: Int): Long = position.toLong()

On closer inspection, we remembered that we already solved this problem for the AwesomeBar which needed unique namespaced IDs for each suggestion.

We can follow the same strategy to solve the problem in the TabsAdapter. 🎉