fix: facet fails on geoshape

[ChiaLingWeng]

This will close #3729.

Through this fix can solve current problem, I'm not sure if this is where the issue lies. Let me know if there's any suggestion.

[joelostblom]

Exciting! Thank you @ChiaLingWeng ! I added an example showing how this works with the code from #3729 (even if that case is more suitable to be used with repeat I think it still illustrates that geo faceting now works).

Let's wait for someone else to have a chance to review the code.

[domoritz]

Thanks for the pull request. The fix looks a bit brittle to me as it assumes that the data in the component has a particular order. I don't think I want to merge this without a deeper analysis of the issue and why the fix is correct. Could you look a bit deeper into it?

[domoritz]

https://github.com/vega/vega-lite/issues/3729 has some analysis.

Also, note how existing examples are changing in this pull request which definitely is a red flag.

[domoritz]

@ChiaLingWeng can you wrap up this pull request?

[ChiaLingWeng]

Hi @domoritz, I'll try to close this, but feel free if you want to take it or provide any suggestion!

[domoritz]

Thanks for working on wrapping this up. Can you try to make the tests run on your fork?