Function processMessage

packages/cli/src/util/dev/builder-worker.cjs:37–108

(message)

}

async function processMessage(message) {
  const { requirePath, buildOptions } = message;
  const builder = require(requirePath);

  // Convert the `files` to back into `FileFsRef` instances
  for (const name of Object.keys(buildOptions.files)) {
    const ref = Object.assign(
      Object.create(FileFsRef.prototype),
      buildOptions.files[name]
    );
    buildOptions.files[name] = ref;
  }

  let result = await builder.build(buildOptions);

  // `@vercel/next` sets this, but it causes "Converting circular
  // structure to JSON" errors, so delete the property...
  delete result.childProcesses;

  // Unwrap BuildResultVX (builder.version === -1) to the actual V2 or V3 result.
  // effectiveVersion reflects the actual result version for downstream checks.
  let effectiveVersion = builder.version;
  if (builder.version === -1) {
    effectiveVersion = result.resultVersion;
    result = result.result;
  }

  // Helper to handle zipBuffer - writes to temp file if too large for IPC
  async function processLambdaOutput(output) {
    const zipBuffer = await output.createZip();
    // Delete files after creating zip to avoid OOM when serializing via IPC.
    // The zipBuffer contains all file data, so files is no longer needed.
    delete output.files;

    // For large zip buffers, write to a temp file instead of sending via IPC.
    // JSON serialization of large Buffers causes OOM because each byte becomes
    // a separate array element (e.g., {"type":"Buffer","data":[1,2,3,...]}).
    if (zipBuffer.length > ZIP_BUFFER_FILE_THRESHOLD) {
      const tempDir = os.tmpdir();
      const randomId = crypto.randomBytes(8).toString('hex');
      const zipFilePath = path.join(
        tempDir,
        `vercel-dev-lambda-${randomId}.zip`
      );
      fs.writeFileSync(zipFilePath, zipBuffer);
      output.zipBufferPath = zipFilePath;
    } else {
      output.zipBuffer = zipBuffer;
    }
  }

  // Container Lambdas carry an OCI image reference in `handler`, not a code
  // bundle, so there is nothing to zip. They are built and run locally by the
  // builder's `startDevServer`; calling `createZip()` on them would throw since
  // the output is a plain image-reference object.
  const isZippableLambda = output =>
    output.type === 'Lambda' && output.runtime !== 'container';