I register a code action provider using the following code action kinds "quickfix" and "source.fixAll.eslint".

Now add the following to the settings json

{
    "editor.codeActionsOnSave": {
        "source.fixAll": true,
        "source.fixAll.eslint": true,
    }
}

Observe the code action provider is called twice on the same save. IMO the provider should only be called once.