Function resolveEsmEntry

test/implementation-option.test.js:33–66

* Resolve the absolute `file:` URL that `await import(specifier)` from inside * `src/` would land on. Walks the package's `exports` field preferring the * `node` / `import` / `default` conditions, falling back to `module` / `main`. * Used to key `mock.module` so the loader's dynamic `import("sass

(specifier)

 * @returns {string} `file:` URL of the package's ESM entry
 */
function resolveEsmEntry(specifier) {
  const pkgPath = findPackageJSON(
    specifier,
    new URL("../src/utils.js", import.meta.url),
  );
  const pkg = JSON.parse(readFileSync(pkgPath, "utf8"));

  const walk = (node) => {
    if (typeof node === "string") return node;
    if (Array.isArray(node)) {
      for (const item of node) {
        const r = walk(item);
        if (r) return r;
      }
    }
    if (node && typeof node === "object") {
      for (const key of ["node", "import", "default"]) {
        if (key in node) {
          const r = walk(node[key]);
          if (r) return r;
        }
      }
    }
    return null;
  };

  const entry =
    (pkg.exports && walk(pkg.exports["."] ?? pkg.exports)) ??
    pkg.module ??
    pkg.main ??
    "index.js";

  return pathToFileURL(path.join(path.dirname(pkgPath), entry)).href;
}

const sassEsmURL = resolveEsmEntry("sass");
const sassEmbeddedEsmURL = resolveEsmEntry("sass-embedded");