How to use namespace in vite

//Test.ts
namespace Test {
  export const a = 123;
}

//main.ts
/// <reference path="./Test.ts" />
console.log(Test.a);

vite run build:

(function polyfill() {
  const relList = document.createElement("link").relList;
  if (relList && relList.supports && relList.supports("modulepreload")) {
    return;
  }
  for (const link of document.querySelectorAll('link[rel="modulepreload"]')) {
    processPreload(link);
  }
  new MutationObserver((mutations) => {
    for (const mutation of mutations) {
      if (mutation.type !== "childList") {
        continue;
      }
      for (const node of mutation.addedNodes) {
        if (node.tagName === "LINK" && node.rel === "modulepreload")
          processPreload(node);
      }
    }
  }).observe(document, { childList: true, subtree: true });
  function getFetchOpts(script) {
    const fetchOpts = {};
    if (script.integrity)
      fetchOpts.integrity = script.integrity;
    if (script.referrerpolicy)
      fetchOpts.referrerPolicy = script.referrerpolicy;
    if (script.crossorigin === "use-credentials")
      fetchOpts.credentials = "include";
    else if (script.crossorigin === "anonymous")
      fetchOpts.credentials = "omit";
    else
      fetchOpts.credentials = "same-origin";
    return fetchOpts;
  }
  function processPreload(link) {
    if (link.ep)
      return;
    link.ep = true;
    const fetchOpts = getFetchOpts(link);
    fetch(link.href, fetchOpts);
  }
})();
console.log(Test.a);

Obviously the bundle has no reference to Test which will introduce a runtime error

How to tell vite to include the namespace in the bundle output？