Function Descriptor

pkg/v1/partial/with.go:310–351

Descriptor returns a v1.Descriptor given a Describable. It also encodes some logic for unwrapping things that have been wrapped by CompressedToLayer, UncompressedToLayer, CompressedToImage, or UncompressedToImage.

(d Describable)

// CompressedToLayer, UncompressedToLayer, CompressedToImage, or
// UncompressedToImage.
func Descriptor(d Describable) (*v1.Descriptor, error) {
	// If Describable implements Descriptor itself, return that.
	if wd, ok := unwrap(d).(withDescriptor); ok {
		return wd.Descriptor()
	}

	// If all else fails, compute the descriptor from the individual methods.
	var (
		desc v1.Descriptor
		err  error
	)

	if desc.Size, err = d.Size(); err != nil {
		return nil, err
	}
	if desc.Digest, err = d.Digest(); err != nil {
		return nil, err
	}
	if desc.MediaType, err = d.MediaType(); err != nil {
		return nil, err
	}
	if wat, ok := d.(withArtifactType); ok {
		if desc.ArtifactType, err = wat.ArtifactType(); err != nil {
			return nil, err
		}
	} else {
		if wrm, ok := d.(WithRawManifest); ok && desc.MediaType.IsImage() {
			mf, _ := Manifest(wrm)
			// Failing to parse as a manifest should just be ignored.
			// The manifest might not be valid, and that's okay.
			if mf != nil {
				if mf.ArtifactType != "" {
					desc.ArtifactType = mf.ArtifactType
				} else {
					desc.ArtifactType = string(mf.Config.MediaType)
				}
			}
		}
	}

	return &desc, nil
}

type withArtifactType interface {
	ArtifactType() (string, error)