Vue.js version

1.0.20

Reproduction Link

https://jsfiddle.net/ardoramor/hyk86ca3/

Steps to reproduce

Run fiddle, examine console.

What is Expected?

Entries will be tracked by the specified path, just like in filters (e.g., orderBy)

What is actually happening?

VueJs prints out a warning and fails to get the unique value specified by path

Required change

There are three lines that would need to change from value[trackByKey] to getPath(value, trackByKey) in functions cacheFrag, getCachedFrag, and deleteCachedFrag. I can make a PR but maybe such a small change doesn't require it?

Also, is it possible to add expression evaluation for track-by? This way, a combination of fields can yield a unique identifier (e.g., track-by="employee.company + employee.id", in case id can be reused by companies). I have a different application but this should make sense as well.