function initFeatureFlags() {
    let needWarn = false;
    if (typeof __VUE_I18N_FULL_INSTALL__ !== 'boolean') {
        needWarn = true;
        getGlobalThis().__VUE_I18N_FULL_INSTALL__ = true;
    }
    if (typeof __VUE_I18N_LEGACY_API__ !== 'boolean') {
        needWarn = true;
        getGlobalThis().__VUE_I18N_LEGACY_API__ = true;
    }
    if (typeof __VUE_I18N_PROD_DEVTOOLS__ !== 'boolean') {
        needWarn = true;
        getGlobalThis().__VUE_I18N_PROD_DEVTOOLS__ = false;
    }
    if (typeof __INTLIFY_PROD_DEVTOOLS__ !== 'boolean') {
        getGlobalThis().__INTLIFY_PROD_DEVTOOLS__ = false;
    }
    if ((process.env.NODE_ENV !== 'production') && typeof true === 'boolean') {
        needWarn = true;
    }
    if ((process.env.NODE_ENV !== 'production') && needWarn) {
        console.warn(`You are running the esm-bundler build of vue-i18n. It is recommended to ` +
            `configure your bundler to explicitly replace feature flag globals ` +
            `with boolean literals to get proper tree-shaking in the final bundle.`);
    }
}
This is only called in esm-bundler builds.
istanbul-ignore-next