Index issue with CBL 2.1

Creating an index over a nested property can cause an existing query to break, as a selected property will now return a blob instead of a dictionary.

Steps to reproduce

• Run app
• Create some documents
• Tap "Create ok index". Note that query still runs successfully (can push "Update" to re-query).
• Tap "Delete indexes".
• Tap "Create problem index". Note that same query breaks immediately as it now returns a blob.
• Deleting index restores working app.

Explanation

The documents being stored are of the form:

{ "counter": 1,
  "nested": { "value": 2 }
}

The query remains the same, selecting document id, counter, and nested properties.

Creating an index over counter property works fine. Creating an index that includes nested changes the form of the result returned via the query which breaks the previously working code.

    fun createIndexWithoutNested() {
        database.createIndex(
            "sampleIndex", IndexBuilder.valueIndex(
                ValueIndexItem.property("counter")
            )
        )
    }

    fun createIndexIncludingNested() {
        database.createIndex(
            "sampleIndex", IndexBuilder.valueIndex(
                ValueIndexItem.property("counter"),
                ValueIndexItem.property("nested")
            )
        )
    }

Credit

Thanks to Valery Miskevich for quickly coding up this sample.