Function startDevServer

packages/container/src/dev.ts:438–466

(
  options: StartDevServerOptions
)

 * the app can honor, and returns the host port for the dev proxy to target.
 */
export async function startDevServer(
  options: StartDevServerOptions
): Promise<StartDevServerResult> {
  // Reuse a live container for this service instead of rebuilding/running on
  // every request. The dev server calls `startDevServer` per request; a
  // container is a persistent server, so we hand back the running one.
  const reuseKey = containerReuseKey(options);
  const existing = runningContainers.get(reuseKey);
  if (existing && existing.isRunning()) {
    return existing.result;
  }
  if (existing) {
    // Stale (exited) entry — clear it before starting a replacement.
    runningContainers.delete(reuseKey);
  }

  // Coalesce concurrent cold starts: if a start for this service is already in
  // flight, wait on it rather than spawning a second container.
  const inFlight = pendingContainers.get(reuseKey);
  if (inFlight) {
    return inFlight;
  }

  const startPromise = startContainer(options, reuseKey).finally(() => {
    pendingContainers.delete(reuseKey);
  });
  pendingContainers.set(reuseKey, startPromise);
  return startPromise;
}

async function startContainer(
  options: StartDevServerOptions,