/**
     * Gets the user Toolchains source.
     *
     * @return the user Toolchains source or {@code null} if none
     */
    @Nonnull
    Optional<Source> getUserToolchainsSource();

    @Nonnull
    static ToolchainsBuilderRequest build(
            @Nonnull ProtoSession session,
            @Nullable Source installationToolchainsFile,
            @Nullable Source userToolchainsSource) {

        this.globalToolchainsSource = globalToolchainsSource;
        return this;
    }

    @Override
    public Source getUserToolchainsSource() {
        return userToolchainsSource;
    }

    @Override
    public ToolchainsBuildingRequest setUserToolchainsSource(Source userToolchainsSource) {
        this.userToolchainsSource = userToolchainsSource;

    /**
     * Gets the user toolchains source.
     *
     * @return The user toolchains source or {@code null} if none.
     */
    Source getUserToolchainsSource();

    /**
     * Sets the user toolchains source. If both user toolchains and a global toolchains are given, the user toolchains
     * take precedence.
     *

        PersistedToolchains globalToolchains = readToolchains(request.getGlobalToolchainsSource(), request, problems);

        PersistedToolchains userToolchains = readToolchains(request.getUserToolchainsSource(), request, problems);

        toolchainsMerger.merge(userToolchains, globalToolchains, TrackableBase.GLOBAL_LEVEL);

        problems.setSource("");

        slf4jLogger.debug(
                "Reading user toolchains from '{}'",
                getLocation(toolchainsRequest.getUserToolchainsSource(), userToolchainsFile));

        ToolchainsBuildingResult toolchainsResult = toolchainsBuilder.build(toolchainsRequest);

        eventSpyDispatcher.onEvent(toolchainsResult);