import {TRANSFORM_TYPES} from '../stdio/type.js'; /* Retrieve the `objectMode`s of a single transform. `objectMode` determines the return value's type, i.e. the `readableObjectMode`. The chunk argument's type is based on the previous generator's return value, i.e. the `writableObjectMode` is based on the previous `readableObjectMode`. The last input's generator is read by `subprocess.stdin` which: - should not be in `objectMode` for performance reasons. - can only be strings, Buffers and Uint8Arrays. Therefore its `readableObjectMode` must be `false`. The same applies to the first output's generator's `writableObjectMode`. */ export const getTransformObjectModes = (objectMode, index, newTransforms, direction) => direction === 'output' ? getOutputObjectModes(objectMode, index, newTransforms) : getInputObjectModes(objectMode, index, newTransforms); const getOutputObjectModes = (objectMode, index, newTransforms) => { const writableObjectMode = index !== 0 && newTransforms[index - 1].value.readableObjectMode; const readableObjectMode = objectMode ?? writableObjectMode; return {writableObjectMode, readableObjectMode}; }; const getInputObjectModes = (objectMode, index, newTransforms) => { const writableObjectMode = index === 0 ? objectMode === true : newTransforms[index - 1].value.readableObjectMode; const readableObjectMode = index !== newTransforms.length - 1 && (objectMode ?? writableObjectMode); return {writableObjectMode, readableObjectMode}; }; // Retrieve the `objectMode` of a file descriptor, e.g. `stdout` or `stderr` export const getFdObjectMode = (stdioItems, direction) => { const lastTransform = stdioItems.findLast(({type}) => TRANSFORM_TYPES.has(type)); if (lastTransform === undefined) { return false; } return direction === 'input' ? lastTransform.value.writableObjectMode : lastTransform.value.readableObjectMode; };