Function deduceContainerPlatform

daemon/migration.go:51–96

deduceContainerPlatform tries to deduce `ctr`'s platform. If both `ctr.OS` and `ctr.ImageManifest` are empty, assume the image comes from a pre-OS times and use the host platform to match the behavior of [container.FromDisk]. Otherwise: - `ctr.ImageManifest.Platform` is used, if it exists and is not

(
	ctx context.Context,
	migration platformReader,
	ctr *container.Container,
)

// `ctr.ImageID`) is used – this looks for the best *present* matching manifest in
// the store.
func deduceContainerPlatform(
	ctx context.Context,
	migration platformReader,
	ctr *container.Container,
) (ocispec.Platform, error) {
	if ctr.OS == "" && ctr.ImageManifest == nil { //nolint:staticcheck // ignore SA1019 because we are testing deprecated field migration
		return platforms.DefaultSpec(), nil
	}

	var errs []error
	isValidPlatform := func(p ocispec.Platform) bool {
		return p.OS != "" && p.Architecture != ""
	}

	if ctr.ImageManifest != nil {
		if ctr.ImageManifest.Platform != nil {
			return *ctr.ImageManifest.Platform, nil
		}

		if ctr.ImageManifest != nil {
			p, err := migration.ReadPlatformFromConfigByImageManifest(ctx, *ctr.ImageManifest)
			if err != nil {
				errs = append(errs, err)
			} else {
				if isValidPlatform(p) {
					return p, nil
				}
				errs = append(errs, errors.New("malformed image config obtained by ImageManifestDescriptor"))
			}
		}
	}

	if ctr.ImageID != "" {
		p, err := migration.ReadPlatformFromImage(ctx, ctr.ImageID)
		if err != nil {
			errs = append(errs, err)
		} else {
			if isValidPlatform(p) {
				return p, nil
			}
			errs = append(errs, errors.New("malformed image config obtained by image id"))
		}
	}

	return ocispec.Platform{}, errors.Wrap(multierror.Join(errs...), "cannot deduce the container platform")
}

type daemonPlatformReader struct {
	imageService ImageService