What version of Ajv you are you using?

6.9.1

What problem do you want to solve?

When using ajv with useDefaults: true, the default keyword is ignored in some cases, as documented in the readme. If someone is aware of the existence of the default keyword but isn't familiar with the details of where it can be used, they might inadvertently use it in a place where it's ignored, resulting in a buggy schema. (This recently caused some bugs in ESLint rules -- also see eslint/eslint#11427.)

We'd like to detect this problem so that schema authors can fix the issue. As far as I can tell, there isn't a simple way for an external tool to figure out whether an ignored default keyword exists in a user-provided schema, without reimplementing some of the logic from ajv.

What do you think is the correct solution to problem?

It should be possible to opt into a mode where invalid default keywords result in a compilation or validation error, rather than being ignored. It seems like this could in principle be added to the meta-schema, although it could make the meta-schema substantially larger. Another possibility could be to add an option to the Ajv constructor that causes this case to throw an error.

Will you be able to implement it?

I'm willing to give it a shot if there is agreement that this is worthwhile.