Function getFormat

src/esm.ts:290–371

(
    url: string,
    context: {},
    defaultGetFormat: typeof getFormat
  )

  }

  async function getFormat(
    url: string,
    context: {},
    defaultGetFormat: typeof getFormat
  ): Promise<{ format: NodeLoaderHooksFormat }> {
    const defer = (overrideUrl: string = url) =>
      defaultGetFormat(overrideUrl, context, defaultGetFormat);

    // See: https://github.com/nodejs/node/discussions/41711
    // nodejs will likely implement a similar fallback.  Till then, we can do our users a favor and fallback today.
    async function entrypointFallback(
      cb: () => ReturnType<typeof getFormat>
    ): ReturnType<typeof getFormat> {
      try {
        return await cb();
      } catch (getFormatError) {
        if (!rememberIsProbablyEntrypoint.has(url)) throw getFormatError;
        return { format: 'commonjs' };
      }
    }

    const parsed = parseUrl(url);

    if (!isFileUrlOrNodeStyleSpecifier(parsed)) {
      return entrypointFallback(defer);
    }

    const { pathname } = parsed;
    assert(
      pathname !== null,
      'ESM getFormat() hook: URL should never have null pathname'
    );

    const nativePath = fileURLToPath(url);

    let nodeSays: { format: NodeLoaderHooksFormat };

    // If file has extension not understood by node, then ask node how it would treat the emitted extension.
    // E.g. .mts compiles to .mjs, so ask node how to classify an .mjs file.
    const ext = extname(nativePath);
    const tsNodeIgnored = tsNodeService.ignored(nativePath);
    const nodeEquivalentExt = extensions.nodeEquivalents.get(ext);
    if (nodeEquivalentExt && !tsNodeIgnored) {
      nodeSays = await entrypointFallback(() =>
        defer(formatUrl(pathToFileURL(nativePath + nodeEquivalentExt)))
      );
    } else {
      try {
        nodeSays = await entrypointFallback(defer);
      } catch (e) {
        if (
          e instanceof Error &&
          tsNodeIgnored &&
          extensions.nodeDoesNotUnderstand.includes(ext)
        ) {
          e.message +=
            `\n\n` +
            `Hint:\n` +