linter error message is confusing

[wbamberg]

If an identifier contains disallowed characters, then the linter's message is:

   item['path']['to']['item']['parent'] should NOT have additional properties

This is wrong and misleading, and it would be much more helpful to say something like:

   item['path']['to']['item'] key contains disallowed characters

...even better if it could link to docs for allowed characters, but https://github.com/mdn/browser-compat-data/blob/master/schemas/compat-data-schema.md does not seem to document this.

[wbamberg]

Actually it's not wrong, it's just unhelpful.

The schema says https://github.com/mdn/browser-compat-data/blob/master/schemas/compat-data.schema.json#L197-L206, i.e. "identifiers can only contain '__compat' or properties matching that regex, no other properties".

ajv then applies that to the data and says "wait, there are other properties", which is correct but usually not a helpful error message.

[Elchi3]

We might want to look for upstream issues on this or file this issue upstream with ajv.

[queengooborg]

It's been a while since we've looked into this one. Looking around, I found that ajv has another package that allows for adding custom error messages on schema failure: ajv-errors. Assuming it plays well with better-ajv-errors, I think this could solve our issue. My pull request for better-ajv-errors was merged to ensure that we can use both of them, so we can now add a custom message!