over riding the var defined in include var file is making all other variables undefined

[Shashank Dutt Jha]

I have included var file using

var_files:

  - file

It has a variable city. state among others

Then I redefine the city variable in a json file and run the playbook --extra-vars "@a.json"

Now when I access any variable other then city it gives undefined var.

[Shashank Dutt Jha]

Should I over-ride all variables? Looks like that.

Or can I selectively decide to over ride only few of them. This is what I want.