Concourse extension confused by docker-image resource type

[marco-m]

Hello,

consider a pipeline beginning with:

resource_types:

- name: docker-image
  privileged: true
  type: docker-image
  source:
    repository: concourse/docker-image-resource

This seems bizarre at first, on the other hand the repetition of docker-image in the name: and type: is needed, since docker-image is a special one.

The stanza above uses the built-in docker-image to download this new docker-image and use it during the pipeline. Confusing at first but it works :-)

The extension is confused and reports an non existing error:

[kdvolder]

The error is not really because the name and type are the same (this odd also, but I don't think we actually check for this). The reason it gives the error is because the name in name: docker-image is already defined as a resource type.

I can probably add some sort of a check to special case built-in resource types like docker-image and allow them to be redefined. Is there a good reason why you want to do something like this? It seems a bit odd and circular to me. Why couldn't you just call it my-docker-image or custom-docker-image or something like that? Wouldn't that actually be cleaner than overwriting an existing resource type?

Anyhoo, I can probably make this error 'go away'. I'd just like to understand a bit better first... to make sure it is really a good idea to forego the check.

[marco-m]

Thanks for the quick answer!
The use case is the same than overwriting another built-in resource like s3 or git: use in the pipeline the new version, obtained from the docker registry, and not the built-in. The reason to do so can be:

• use a new feature of the resource
• a bugfix
• testing a specific version, maybe a fork, of the resource itself

Does it make sense?

[kdvolder]

Does it make sense?

Yes... and no. I guess if I was going to use an alternate implementation, of a builltin resource type, I'd probably just give it a different name. Anyhoo, I guess that's just me. Seems like, though this probably not common, we should probably assume people may do this kind of redefinition, and it shouldn't be flagged as a error by the editor.

[marco-m]

Wow thanks @kdvolder I appreciate!