Function getSourceFilePathFromPage

packages/next/src/utils.ts:1754–1863

({
  workPath,
  page,
  pageExtensions,
  nextVersion,
}: {
  workPath: string;
  page: string;
  pageExtensions?: ReadonlyArray<string>;
  nextVersion?: string;
})

}

async function getSourceFilePathFromPage({
  workPath,
  page,
  pageExtensions,
  nextVersion,
}: {
  workPath: string;
  page: string;
  pageExtensions?: ReadonlyArray<string>;
  nextVersion?: string;
}) {
  const usesSrcDir = await usesSrcDirectory(workPath);
  const extensionsToTry = pageExtensions || ['js', 'jsx', 'ts', 'tsx'];

  // In Next.js 16+, check for proxy.ts first as it's the recommended replacement for middleware.ts
  const isNextJs16Plus = nextVersion && semver.gte(nextVersion, '16.0.0');
  const pagesToCheck =
    page === 'middleware' && isNextJs16Plus
      ? ['proxy', 'middleware'] // Check proxy.ts first in Next.js 16+
      : [page];

  for (const pageToCheck of pagesToCheck) {
    for (const pageType of [
      // middleware/proxy is not nested in pages/app
      ...(pageToCheck === 'middleware' || pageToCheck === 'proxy'
        ? ['']
        : ['pages', 'app']),
    ]) {
      let fsPath = path.join(workPath, pageType, pageToCheck);
      if (usesSrcDir) {
        fsPath = path.join(workPath, 'src', pageType, pageToCheck);
      }

      if (fs.existsSync(fsPath)) {
        return path.relative(workPath, fsPath);
      }
      const extensionless = fsPath.replace(path.extname(fsPath), '');

      for (const ext of extensionsToTry) {
        fsPath = `${extensionless}.${ext}`;
        // for appDir, we need to treat "index.js" as root-level "page.js"
        if (
          pageType === 'app' &&
          extensionless ===
            path.join(workPath, `${usesSrcDir ? 'src/' : ''}app/index`)
        ) {
          fsPath = `${extensionless.replace(/index$/, 'page')}.${ext}`;
        }
        if (fs.existsSync(fsPath)) {
          return path.relative(workPath, fsPath);
        }
      }

      if (isDirectory(extensionless)) {
        if (pageType === 'pages') {
          for (const ext of extensionsToTry) {
            fsPath = path.join(extensionless, `index.${ext}`);
            if (fs.existsSync(fsPath)) {