New Platform Config service should support deprecations

[mshustov]

A migrated to New platform plugin uses NP Config service, which doesn't support Deprecations yet. It means plugins have to tweak config schema, config values and log warnings manually.
Legacy platform config uses a separate module for deprecations https://github.com/restrry/kibana/blob/0f25401fe4caaf97ff1b701d245455a0ef71ec3a/src/legacy/server/config/transform_deprecations.js#L75

[elasticmachine]

Pinging @elastic/kibana-platform

[epixa]

Why is handling deprecations manually a problem? It seems like a pretty trivial thing to wrap a warning log in a conditional.

[mshustov]

It's not only about logging a warning message.

Config Schema

A user has to specify the config schema. When one property deprecated in favor of another one schema looks like:

• NewProperty should be validated if present in config.
• OldProperty should be validated if NewProperty is not defined.
• throw an error is both NewProperty and OldProperty are present in the config.

At least we can do here is to provide a @kbn/config-schema helper for this logic.

Config Value

A user has to calculate a value manually.

const value = config.NewProperty || config.OldProperty

[epixa]

Makes sense, thanks for the explanation.