Function generateManifest

internal/oci/push.go:162–223

(layers []v1.Descriptor, ociCompat api.OCIVersion)

}

func generateManifest(layers []v1.Descriptor, ociCompat api.OCIVersion) (v1.Descriptor, []v1.Descriptor, error) {
	var toPush []v1.Descriptor
	var config v1.Descriptor
	var artifactType string
	switch ociCompat {
	case api.OCIVersion1_0:
		// "Content other than OCI container images MAY be packaged using the image manifest.
		// When this is done, the config.mediaType value MUST be set to a value specific to
		// the artifact type or the empty value."
		// Source: https://github.com/opencontainers/image-spec/blob/main/manifest.md#guidelines-for-artifact-usage
		//
		// The `ComposeEmptyConfigMediaType` is used specifically for this purpose:
		// there is no config, and an empty descriptor is used for OCI 1.1 in
		// conjunction with the `ArtifactType`, but for OCI 1.0 compatibility,
		// tooling falls back to the config media type, so this is used to
		// indicate that it's not a container image but custom content.
		configData := []byte("{}")
		config = v1.Descriptor{
			MediaType: ComposeEmptyConfigMediaType,
			Digest:    digest.FromBytes(configData),
			Size:      int64(len(configData)),
			Data:      configData,
		}
		// N.B. OCI 1.0 does NOT support specifying the artifact type, so it's
		//		left as an empty string to omit it from the marshaled JSON
		artifactType = ""
		toPush = append(toPush, config)
	case api.OCIVersion1_1:
		config = v1.DescriptorEmptyJSON
		artifactType = ComposeProjectArtifactType
		toPush = append(toPush, config)
	default:
		return v1.Descriptor{}, nil, fmt.Errorf("unsupported OCI version: %s", ociCompat)
	}

	manifest, err := json.Marshal(v1.Manifest{
		Versioned:    specs.Versioned{SchemaVersion: 2},
		MediaType:    v1.MediaTypeImageManifest,
		ArtifactType: artifactType,
		Config:       config,
		Layers:       layers,
		Annotations: map[string]string{
			"org.opencontainers.image.created": time.Now().Format(time.RFC3339),
		},
	})
	if err != nil {
		return v1.Descriptor{}, nil, err
	}

	manifestDescriptor := v1.Descriptor{
		MediaType: v1.MediaTypeImageManifest,
		Digest:    digest.FromString(string(manifest)),
		Size:      int64(len(manifest)),
		Annotations: map[string]string{
			"com.docker.compose.version": api.ComposeVersion,
		},
		ArtifactType: artifactType,
		Data:         manifest,