Refactor: Use Classes for platforms

[rarkins]

We should add a Class for Platforms to ensure that all implementations have the correct/required functions, and to reduce duplicated code.

[JamieMagee]

@rarkins I'm looking at this now, but for datasources instead of platforms.

I think datasources (in general) are simpler than platforms, and I want to do this for datasources to reduce the duplicated error handling code that I noticed when implementing #6284

[rarkins]

@JamieMagee sounds good. I'd also hoped that we can reduce the amount of duplicated code in datasources soon, especially in error handling. I had been thinking to do most of the heavy lifting in lib/datasource/index.ts though, and hadn't thought about classes. Anything that reduces the amount of boilerplate code per datasource would be great.

Something important to keep in mind: I think users will need the ability to override defaults for things like:

• Should errors from host X throw a datasource error or be ignored?
• How should different error codes be treated per host?

Today we only throw datasource errors for known public resources that should never go down like npmjs and pypi, and also a lot of users seem happy to ignore errors from private registries they haven't provided us authentication details for. However there's also a middle ground of people using private registries where if it goes down temporarily then we don't throw a datasource error and instead usually end up autoclosing any PRs from it.

[viceice]

Having a config options for error would be great. I would prefer to always throw datasource errors on our private registries, as they are unreachable more often.

This happens when renovate automerge a patch or digest update and our jenkins deploays the update, which can cause a registry down time of a few seconds. so if renovate tries to fetch updates from that it will silently fail and close all pr's.

[JamieMagee]

Yeah, I think a config option would be possible. All the public repos are well known (docker.com, npmjs.com, etc.) so we can do a simple check like

if (isPublicDatasource(url) || config.throwOnPrivateDatasources) {
  throw new ...
}

[viceice]

Maybe we should split this feature for platfroms / datasources / versionings / mangers to have separate issues?

[JamieMagee]

@viceice Can we just keep this 1 for now? I can experiment and see how it works out before we start committing to all the work.

[viceice]

@JamieMagee Ok, as you like 🙃