Here I have a doubt that there is no reason for the validation of the mediatype field, because the mediatype field is optional and not always present in the descriptor.

It might be better to combine this into a function that tells whether or not a mediatype is a layer, although, this validation may be too strict.

It might be better to combine this into a function that tells whether or not a mediatype is a layer, although, this validation may be too strict.

@stevvooe The judgment here is only a warning, not an error. So it can not be said that the conditions are not layers.So I do not think your idea is good.

LGTM

@wking As @q384566678 said, this is only a warning -- the discussion inside opencontainers/image-tools#111 is not completely valid (this schema validator is not meant to error on unknown layer types).

@philips @jonboulle @stevvooe PTAL

lgtm

As @cyphar said, this is probably too aggressive.