public List<Artifact> getMissingArtifacts() {
        return missingArtifacts == null ? Collections.emptyList() : Collections.unmodifiableList(missingArtifacts);
    }

    public MetadataResolutionResult addMissingArtifact(Artifact artifact) {
        missingArtifacts = initList(missingArtifacts);

        missingArtifacts.add(artifact);

        return this;
    }

    public List<Artifact> getMissingArtifacts() {
        return missingArtifacts == null ? Collections.emptyList() : Collections.unmodifiableList(missingArtifacts);
    }

    public ArtifactResolutionResult addMissingArtifact(Artifact artifact) {
        missingArtifacts = initList(missingArtifacts);

        missingArtifacts.add(artifact);

        return this;
    }

            } catch (ArtifactResolutionException e) {
                result.addErrorArtifactException(e);
                return result;
            } catch (ArtifactNotFoundException e) {
                result.addMissingArtifact(request.getArtifact());
                return result;
            }
        }

        ArtifactResolutionRequest collectionRequest = request;

        if (request.isResolveTransitively()) {