GetDigest could skip API call when passed a digest

[wholtz]

Currently, GetDigest does an API call to translate any image reference into a digest. But if the image reference contains a digest and not a tag, is there a reason why the digest should not be parsed out of the image reference, thus saving an API call?

image/docker/docker_image.go

Line 120 in 0e74274

func GetDigest(ctx context.Context, sys *types.SystemContext, ref types.ImageReference) (digest.Digest, error) {

[mtrmac]

Thanks for your report.

I mean, the caller of this API is by definition specialized to do a tag resolution operation, so that caller could just … not use this?

I don’t have a strong opinion on whether the “is the reference to resolve a tag or a digest” ideally belongs inside GetDigest or inside a caller, if that condition really had to exist.

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It’s more that I have a hunch that this might indicate some other design issue in the caller, trying to maintain a reference->digest mapping that doesn’t need to exist, or something like that. Or, well, a caller invoking GetDigest with a digest already known might very well be a natural outcome of some abstraction layering, where that information gets lost…, and preserving that information would be more trouble than it’s worth.

Of course, I know nothing at all about the caller, so take this just as a thing to possibly explore, something you quite likely have a firm and well-justified opinion on.