toolchainModels.put("unknown", Collections.singletonList(new ToolchainModel()));
        executionRequest.setToolchains(toolchainModels);
        when(session.getRequest()).thenReturn(executionRequest);

        List<Toolchain> toolchains = toolchainManager.getToolchains(session, "unknown", null);

        assertEquals(0, toolchains.size());

     */
    @Nonnull
    String getSource();

    /**
     * Gets the one-based index of the line containing the problem. The line number should refer to some text file that
     * is given by {@link #getSource()}.
     *
     * @return the one-based index of the line containing the problem or a non-positive value if unknown
     */
    int getLineNumber();

@Deprecated
public interface ArtifactTransferResource {

    /**
     * The base URL of the repository, e.g. "http://repo1.maven.org/maven2/". Unless the URL is unknown, it will be
     * terminated by a trailing slash.
     *
     * @return The base URL of the repository or an empty string if unknown, never {@code null}.
     */
    String getRepositoryUrl();

    /**
     * The path of the artifact relative to the repository's base URL.
     *

     * @param message The detail message of the problem, may be {@code null}.
     * @param line The one-based index of the line containing the problem or {@code -1} if unknown.
     * @param column The one-based index of the column containing the problem or {@code -1} if unknown.
     * @param cause The cause of the problem, may be {@code null}.
     */
    void add(Problem.Severity severity, String message, int line, int column, Exception cause);

     */
    String getSource();

    /**
     * Gets the one-based index of the line containing the problem. The line number should refer to some text file that
     * is given by {@link #getSource()}.
     *
     * @return The one-based index of the line containing the problem or a non-positive value if unknown.
     */
    int getLineNumber();

    /**

        // execute
        ToolchainPrivate[] toolchains = toolchainManager.getToolchainsForType("unknown", session);

        // verify
        verify(logger).error("Missing toolchain factory for type: unknown. Possibly caused by misconfigured project.");
        assertEquals(0, toolchains.length);
    }

    @Test

     * <groupId>:<artifactId>:<version>} but some of these coordinates may still be unknown at the point the exception
     * is thrown so this information is merely meant to assist the user.
     *
     * @return The identifier of the project or an empty string if not known, never {@code null}.
     */
    String getProjectId();

    /**
     * Gets the POM file from which the project was built.

        boolean modules = false;
        boolean unknown = false;
        for (PathType type : types) {
            if (filter.test(type)) {
                if (JavaPathType.CLASSES.equals(type)) {
                    classes = true;
                } else if (JavaPathType.MODULES.equals(type)) {
                    modules = true;
                } else {
                    unknown = true;
                }

     * If no type is known for {@code id}, the registry will
     * create a custom {@code Type} for it.
     *
     * @param id the id of the type to retrieve
     * @return the type
     */
    @Nonnull
    @Override
    default Type require(@Nonnull String id) {
        return lookup(id).orElseThrow(() -> new IllegalArgumentException("Unknown extensible enum value '" + id + "'"));
    }

        boolean modules = false;
        boolean unknown = false;
        for (PathType type : types) {
            if (filter.test(type)) {
                if (JavaPathType.CLASSES.equals(type)) {
                    classes = true;
                } else if (JavaPathType.MODULES.equals(type)) {
                    modules = true;
                } else {
                    unknown = true;
                }