Function canUseSyncIterablePipeToFastPath

lib/internal/streams/iter/pull.js:132–146

(source, transforms, signal)

}

function canUseSyncIterablePipeToFastPath(source, transforms, signal) {
  if (signal !== undefined ||
      transforms.length !== 0 ||
      isPrimitiveChunk(source) ||
      ArrayIsArray(source) ||
      source?.[kValidatedSource] ||
      !isSyncIterable(source) ||
      isAsyncIterable(source)) {
    return false;
  }

  // Preserve from()'s top-level protocol precedence for custom iterables.
  return typeof source[toAsyncStreamable] !== 'function' &&
    typeof source[toStreamable] !== 'function';
}

// =============================================================================
// Transform Output Flattening