Provide warning when data/watch/computed etc. conflicts with existing Vue object properties

[dz902]

What problem does this feature solve?

I accidentally created a data attribute called language. It seems this attribute conflicts with some existing properties of Vue object.

There were no warnings, but the attribute won't be updated by this.$data.language, it stays as initial value. All other data attributes do work correctly. When console.log(this.$data)'d it shows 2 language properties, one with initial value, the other is dynamic as (...). After changing this attribute to lang everything works.

Considering data/watch/computed etc. all ends up as properties of Vue object, it would be nice to have some warning or exception if there are conflicts.

What does the proposed API look like?

AttributeError: "language" is a reserved property name and should not be avoided.

[posva]

the conflict doesn't come from Vue, it comes from a library adding it. The warning should be implemented there