func dbManifestToManifest()

in registry/handlers/manifests.go [544:614]
51 lines of code
15 McCabe index (conditional complexity)

func dbManifestToManifest(dbm *models.Manifest) (distribution.Manifest, error) {
	if dbm.SchemaVersion == 1 {
		return nil, distribution.ErrSchemaV1Unsupported
	}

	if dbm.SchemaVersion != 2 {
		return nil, fmt.Errorf("unrecognized manifest schema version %d", dbm.SchemaVersion)
	}

	mediaType := dbm.MediaType
	if dbm.NonConformant {
		// parse payload and get real media type
		var versioned manifest.Versioned
		if err := json.Unmarshal(dbm.Payload, &versioned); err != nil {
			return nil, fmt.Errorf("failed to unmarshal manifest payload: %w", err)
		}
		mediaType = versioned.MediaType
	}

	// TODO: Each case here is taken directly from the respective
	// registry/storage/*manifesthandler Unmarshal method. We cannot invoke them
	// directly as they are unexported, but they are relatively simple. We should
	// determine a single place for this logic during refactoring
	// https://gitlab.com/gitlab-org/container-registry/-/issues/135

	// This can be an image manifest or a manifest list
	switch mediaType {
	case schema2.MediaTypeManifest:
		m := &schema2.DeserializedManifest{}
		if err := m.UnmarshalJSON(dbm.Payload); err != nil {
			return nil, err
		}

		return m, nil
	case v1.MediaTypeImageManifest:
		m := &ocischema.DeserializedManifest{}
		if err := m.UnmarshalJSON(dbm.Payload); err != nil {
			return nil, err
		}

		return m, nil
	case manifestlist.MediaTypeManifestList, v1.MediaTypeImageIndex:
		m := &manifestlist.DeserializedManifestList{}
		if err := m.UnmarshalJSON(dbm.Payload); err != nil {
			return nil, err
		}

		return m, nil
	case "":
		// OCI image or image index - no media type in the content

		// First see if it looks like an image index
		resIndex := &manifestlist.DeserializedManifestList{}
		if err := resIndex.UnmarshalJSON(dbm.Payload); err != nil {
			return nil, err
		}
		if resIndex.Manifests != nil {
			return resIndex, nil
		}

		// Otherwise, assume it must be an image manifest
		m := &ocischema.DeserializedManifest{}
		if err := m.UnmarshalJSON(dbm.Payload); err != nil {
			return nil, err
		}

		return m, nil
	default:
		return nil, distribution.ErrManifestVerification{fmt.Errorf("unrecognized manifest content type %s", dbm.MediaType)}
	}
}