execa/lib/stdio/handle.js

Process execution for humans

import {getStreamName, isStandardStream} from '../utils/standard-stream.js';
import {normalizeTransforms} from '../transform/normalize.js';
import {getFdObjectMode} from '../transform/object-mode.js';
import {
	getStdioItemType,
	isRegularUrl,
	isUnknownStdioString,
	isStdioValueObject,
	checkBooleanOption,
	FILE_TYPES,
} from './type.js';
import {getStreamDirection} from './direction.js';
import {normalizeStdioOption} from './stdio-option.js';
import {handleNativeStream} from './native.js';
import {handleInputOptions} from './input-option.js';
import {filterDuplicates, getDuplicateStream} from './duplicate.js';

// Handle `input`, `inputFile`, `stdin`, `stdout` and `stderr` options, before spawning, in async/sync mode
// They are converted into an array of `fileDescriptors`.
// Each `fileDescriptor` is normalized, validated and contains all information necessary for further handling.
export const handleStdio = (addProperties, options, verboseInfo, isSync) => {
	const stdio = normalizeStdioOption(options, verboseInfo, isSync);
	const initialFileDescriptors = stdio.map((stdioOption, fdNumber) => getFileDescriptor({
		stdioOption,
		fdNumber,
		options,
		isSync,
	}));
	const fileDescriptors = getFinalFileDescriptors({
		initialFileDescriptors,
		addProperties,
		options,
		isSync,
	});
	options.stdio = fileDescriptors.map(({stdioItems}) => forwardStdio(stdioItems));
	return fileDescriptors;
};

const getFileDescriptor = ({stdioOption, fdNumber, options, isSync}) => {
	const optionName = getStreamName(fdNumber);
	const {stdioItems: initialStdioItems, isStdioArray} = initializeStdioItems({
		stdioOption,
		fdNumber,
		options,
		optionName,
	});
	const direction = getStreamDirection({
		stdioItems: initialStdioItems,
		isStdioArray,
		fdNumber,
		optionName,
	});
	const stdioItems = initialStdioItems.map(stdioItem => handleNativeStream({
		stdioItem,
		isStdioArray,
		fdNumber,
		direction,
		isSync,
	}));
	const normalizedStdioItems = normalizeTransforms(stdioItems, optionName, direction, options);
	const objectMode = getFdObjectMode(normalizedStdioItems, direction);
	validateFileObjectMode(normalizedStdioItems, objectMode);
	return {direction, objectMode, stdioItems: normalizedStdioItems};
};

// We make sure passing an array with a single item behaves the same as passing that item without an array.
// This is what users would expect.
// For example, `stdout: ['ignore']` behaves the same as `stdout: 'ignore'`.
const initializeStdioItems = ({stdioOption, fdNumber, options, optionName}) => {
	const values = Array.isArray(stdioOption) ? stdioOption : [stdioOption];
	const inputStdioItems = handleInputOptions(options, fdNumber);
	const initialStdioItems = [
		...omitInheritedStdin(values.map(value => initializeStdioItem(value, optionName)), inputStdioItems),
		...inputStdioItems,
	];

	const stdioItems = filterDuplicates(initialStdioItems);
	const isStdioArray = stdioItems.length > 1;
	validateStdioArray(stdioItems, isStdioArray, optionName);
	validateStreams(stdioItems);
	return {stdioItems, isStdioArray};
};

const omitInheritedStdin = (stdioItems, inputStdioItems) => inputStdioItems.length > 0 && isInheritedStdinOnly(stdioItems)
	? []
	: stdioItems;

const isInheritedStdinOnly = stdioItems => stdioItems.length === 1
	&& stdioItems[0].type === 'native'
	&& stdioItems[0].value === 'inherit';

const initializeStdioItem = (value, optionName) => {
	if (isStdioValueObject(value)) {
		return initializeStdioValueObject(value, optionName);
	}

	return {
		type: getStdioItemType(value, optionName),
		value,
		optionName,
	};
};

// The `{value, input}` object form wraps any stdio value with an explicit direction.
const initializeStdioValueObject = ({value, input}, optionName) => {
	checkBooleanOption(input, `${optionName}.input`);

	return {
		type: getStdioItemType(value, optionName),
		value,
		direction: input ? 'input' : undefined,
		optionName,
	};
};

const validateStdioArray = (stdioItems, isStdioArray, optionName) => {
	if (stdioItems.length === 0) {
		throw new TypeError(`The \`${optionName}\` option must not be an empty array.`);
	}

	if (!isStdioArray) {
		return;
	}

	for (const {value, optionName} of stdioItems) {
		if (INVALID_STDIO_ARRAY_OPTIONS.has(value)) {
			throw new Error(`The \`${optionName}\` option must not include \`${value}\`.`);
		}
	}
};

// Using the `ignore` value together with others for the same stream does not make sense, so we make it fail.
// However, we do allow it if the array has a single item.
const INVALID_STDIO_ARRAY_OPTIONS = new Set(['ignore']);

const validateStreams = stdioItems => {
	for (const stdioItem of stdioItems) {
		validateFileStdio(stdioItem);
		validateFileDescriptorStdio(stdioItem);
	}
};

// A number is a file descriptor. Anything else is not a valid one, and passing it to `node:child_process` aborts the current process with a fatal assertion instead of throwing.
const validateFileDescriptorStdio = ({type, value, optionName}) => {
	if (type === 'native' && typeof value === 'number' && (!Number.isInteger(value) || value < 0 || value > MAX_FILE_DESCRIPTOR)) {
		throw new TypeError(`The \`${optionName}\` option must be a non-negative 32-bit integer: got ${value}.`);
	}
};

// `node:child_process` converts file descriptors to a 32-bit signed integer, and aborts the process when it cannot
const MAX_FILE_DESCRIPTOR = (2 ** 31) - 1;

const validateFileStdio = ({type, value, optionName}) => {
	if (isRegularUrl(value)) {
		throw new TypeError(`The \`${optionName}: URL\` option must use the \`file:\` scheme.
For example, you can use the \`pathToFileURL()\` method of the \`url\` core module.`);
	}

	if (isUnknownStdioString(type, value)) {
		throw new TypeError(`The \`${optionName}: { file: '...' }\` option must be used instead of \`${optionName}: '...'\`.`);
	}
};

const validateFileObjectMode = (stdioItems, objectMode) => {
	if (!objectMode) {
		return;
	}

	const fileStdioItem = stdioItems.find(({type}) => FILE_TYPES.has(type));
	if (fileStdioItem !== undefined) {
		throw new TypeError(`The \`${fileStdioItem.optionName}\` option cannot use both files and transforms in objectMode.`);
	}
};

// Some `stdio` values require Execa to create streams.
// For example, file paths create file read/write streams.
// Those transformations are specified in `addProperties`, which is both direction-specific and type-specific.
const getFinalFileDescriptors = ({initialFileDescriptors, addProperties, options, isSync}) => {
	const fileDescriptors = [];

	try {
		for (const fileDescriptor of initialFileDescriptors) {
			addFinalFileDescriptor({
				fileDescriptor,
				fileDescriptors,
				addProperties,
				options,
				isSync,
			});
		}

		return fileDescriptors;
	} catch (error) {
		cleanupCustomStreams(fileDescriptors);
		throw error;
	}
};

/*
The file descriptor is added to `fileDescriptors` before its items are, for two reasons:
  - its items are added one at a time, so that each one knows about the previous ones, to detect duplicates within the same file descriptor
  - if an item throws, the streams created by the previous ones are cleaned up too
*/
const addFinalFileDescriptor = ({fileDescriptor, fileDescriptors, addProperties, options, isSync}) => {
	const {direction, objectMode, stdioItems} = fileDescriptor;
	const finalFileDescriptor = {direction, objectMode, stdioItems: []};
	fileDescriptors.push(finalFileDescriptor);

	for (const stdioItem of stdioItems) {
		finalFileDescriptor.stdioItems.push(addStreamProperties({
			stdioItem,
			addProperties,
			direction,
			options,
			fileDescriptors,
			isSync,
		}));
	}
};

const addStreamProperties = ({stdioItem, addProperties, direction, options, fileDescriptors, isSync}) => {
	const duplicateStream = getDuplicateStream({
		stdioItem,
		direction,
		fileDescriptors,
		isSync,
	});

	if (duplicateStream !== undefined) {
		return {...stdioItem, stream: duplicateStream};
	}

	return {
		...stdioItem,
		...addProperties[direction][stdioItem.type](stdioItem, options),
	};
};

// The stream error handling is performed by the piping logic above, which cannot be performed before subprocess spawning.
// If the subprocess spawning fails (e.g. due to an invalid command), the streams need to be manually destroyed.
// We need to create those streams before subprocess spawning, in case their creation fails, e.g. when passing an invalid generator as argument.
// Like this, an exception would be thrown, which would prevent spawning a subprocess.
export const cleanupCustomStreams = fileDescriptors => {
	for (const {stream} of fileDescriptors.flatMap(({stdioItems}) => stdioItems)) {
		if (stream === undefined || isStandardStream(stream)) {
			continue;
		}

		// The stream can still error after being destroyed, e.g. when its file cannot be opened.
		// That error would be uncaught and crash the current process, although it is irrelevant since execa already fails with its own error.
		stream.on('error', () => {});
		stream.destroy();
	}
};

// When the `std*: Iterable | WebStream | URL | filePath`, `input` or `inputFile` option is used, we pipe to `subprocess.std*`.
// When the `std*: Array` option is used, we emulate some of the native values ('inherit', Node.js stream and file descriptor integer). To do so, we also need to pipe to `subprocess.std*`.
// Therefore the `std*` options must be either `pipe` or `overlapped`. Other values do not set `subprocess.std*`.
const forwardStdio = stdioItems => {
	if (stdioItems.length > 1) {
		return stdioItems.some(({value}) => value === 'overlapped') ? 'overlapped' : 'pipe';
	}

	const [{type, value}] = stdioItems;
	return type === 'native' ? value : 'pipe';
};