Function findBuildMatch

packages/cli/src/util/dev/server.ts:3232–3270

(
  matches: Map<string, BuildMatch>,
  files: BuilderInputs,
  requestPath: string,
  devServer: DevServer,
  vercelConfig: VercelConfig,
  isFilesystem = false
)

}

async function findBuildMatch(
  matches: Map<string, BuildMatch>,
  files: BuilderInputs,
  requestPath: string,
  devServer: DevServer,
  vercelConfig: VercelConfig,
  isFilesystem = false
): Promise<BuildMatch | null> {
  requestPath = requestPath.replace(/^\//, '');

  let bestIndexMatch: undefined | BuildMatch;
  for (const match of matches.values()) {
    if (
      await shouldServe(
        match,
        files,
        requestPath,
        devServer,
        vercelConfig,
        isFilesystem,
        !!bestIndexMatch
      )
    ) {
      if (!isIndex(match.src)) {
        return match;
      } else {
        // If isIndex === true and ends in `.html`, we're done.
        // Otherwise, keep searching.
        if (extname(match.src) === '.html') {
          return match;
        }
        bestIndexMatch = match;
      }
    }
  }

  // return a non-.html index file or none are found
  return bestIndexMatch || null;
}

async function shouldServe(
  match: BuildMatch,