Function onerror

lib/internal/streams/readable.js:1037–1050

(er)

  // If the dest has an error, then stop piping into it.
  // However, don't suppress the throwing behavior for this.
  function onerror(er) {
    debug('onerror', er);
    unpipe();
    dest.removeListener('error', onerror);
    if (dest.listenerCount('error') === 0) {
      const s = dest._writableState || dest._readableState;
      if (s && !s.errorEmitted) {
        // User incorrectly emitted 'error' directly on the stream.
        errorOrDestroy(dest, er);
      } else {
        dest.emit('error', er);
      }
    }
  }

  // Make sure our error handler is attached before userland ones.
  prependListener(dest, 'error', onerror);