Separate smaller core

source/context.js

@@ -4,7 +4,6 @@ import {stripVTControlCharacters} from 'node:util';
 export const getContext = raw => ({
 	start: process.hrtime.bigint(),
 	command: raw.map(part => getCommandPart(stripVTControlCharacters(part))).join(' '),
-	state: {stdout: '', stderr: '', output: ''},
 });
 
 const getCommandPart = part => /[^\w./-]/.test(part)

source/index.js

@@ -1,6 +1,7 @@
 import {getContext} from './context.js';
 import {getOptions} from './options.js';
-import {spawnSubprocess} from './spawn.js';
+import {handleArguments} from './spawn.js';
+import picoSpawn from './pico-spawn.js';
 import {getResult} from './result.js';
 import {handlePipe} from './pipe.js';
 import {lineIterator, combineAsyncIterators} from './iterable.js';
@@ -9,8 +10,9 @@ export default function spawn(file, second, third, previous) {
 	const [commandArguments = [], options = {}] = Array.isArray(second) ? [second, third] : [[], second];
 	const context = getContext([file, ...commandArguments]);
 	const spawnOptions = getOptions(options);
-	const nodeChildProcess = spawnSubprocess(file, commandArguments, spawnOptions, context);
-	let subprocess = getResult(nodeChildProcess, spawnOptions, context);
+	const picoPromise = getPicoSubprocess(file, commandArguments, spawnOptions, context);
+	const nodeChildProcess = getNodeChildProcess(picoPromise);
+	let subprocess = getResult(picoPromise, nodeChildProcess, context, spawnOptions);
 	Object.assign(subprocess, {nodeChildProcess});
 	subprocess = previous ? handlePipe([previous, subprocess]) : subprocess;
 
@@ -24,3 +26,14 @@ export default function spawn(file, second, third, previous) {
 		pipe: (file, second, third) => spawn(file, second, third, subprocess),
 	});
 }
+
+const getPicoSubprocess = async (file, commandArguments, spawnOptions, context) => {
+	const spawnArguments = await handleArguments(file, commandArguments, spawnOptions, context);
+	const picoSubprocess = picoSpawn(...spawnArguments);
+	return {picoSubprocess};
+};
+
+const getNodeChildProcess = async picoPromise => {
+	const {picoSubprocess} = await picoPromise;
+	return picoSubprocess.nodeChildProcess;
+};

source/iterable.js

@@ -1,12 +1,12 @@
-export const lineIterator = async function * (subprocess, {state}, streamName) {
+export const lineIterator = async function * (subprocess, context, streamName) {
 	// Prevent buffering when iterating.
 	// This would defeat one of the main goals of iterating: low memory consumption.
-	if (state.isIterating === false) {
+	if (context.isIterating === false) {
 		throw new Error(`The subprocess must be iterated right away, for example:
 	for await (const line of spawn(...)) { ... }`);
 	}
 
-	state.isIterating = true;
+	context.isIterating = true;
 
 	try {
 		const {[streamName]: stream} = await subprocess.nodeChildProcess;

source/pico-spawn.js

@@ -0,0 +1,90 @@
+import {spawn} from 'node:child_process';
+import {once, on} from 'node:events';
+
+export default function picoSpawn(file, second, third) {
+	const [commandArguments = [], options = {}] = Array.isArray(second) ? [second, third] : [[], second];
+	const state = {
+		stdout: '',
+		stderr: '',
+		output: '',
+		command: [file, ...commandArguments].join(' '),
+	};
+	const nodeChildProcess = spawnSubprocess(file, commandArguments, options, state);
+	return Object.assign(getResult(nodeChildProcess, state), {nodeChildProcess});
+}
+
+const spawnSubprocess = async (file, commandArguments, options, state) => {
+	try {
+		const instance = spawn(file, commandArguments, options);
+		bufferOutput(instance.stdout, 'stdout', options, state);
+		bufferOutput(instance.stderr, 'stderr', options, state);
+
+		// The `error` event is caught by `once(instance, 'spawn')` and `once(instance, 'close')`.
+		// But it creates an uncaught exception if it happens exactly one tick after 'spawn'.
+		// This prevents that.
+		instance.once('error', () => {});
+
+		await once(instance, 'spawn');
+		return instance;
+	} catch (error) {
+		throw getSubprocessError(error, {}, state);
+	}
+};
+
+const bufferOutput = (stream, streamName, {buffer = true}, state) => {
+	if (stream) {
+		stream.setEncoding('utf8');
+		if (buffer) {
+			stream.on('data', chunk => {
+				state[streamName] += chunk;
+				state.output += chunk;
+			});
+		}
+	}
+};
+
+const getResult = async (nodeChildProcess, state) => {
+	const instance = await nodeChildProcess;
+	const onClose = once(instance, 'close');
+
+	try {
+		await Promise.race([
+			onClose,
+			...instance.stdio.filter(Boolean).map(stream => onStreamError(stream)),
+		]);
+		checkFailure(instance, state);
+		return state;
+	} catch (error) {
+		await Promise.allSettled([onClose]);
+		throw getSubprocessError(error, instance, state);
+	}
+};
+
+const onStreamError = async stream => {
+	for await (const [error] of on(stream, 'error')) {
+		// Ignore errors that are due to closing errors when the subprocesses exit normally, or due to piping
+		if (!['ERR_STREAM_PREMATURE_CLOSE', 'EPIPE'].includes(error?.code)) {
+			throw error;
+		}
+	}
+};
+
+const checkFailure = ({exitCode, signalCode}, {command}) => {
+	if (signalCode) {
+		throw new Error(`Command was terminated with ${signalCode}: ${command}`);
+	}
+
+	if (exitCode >= 1) {
+		throw new Error(`Command failed with exit code ${exitCode}: ${command}`);
+	}
+};
+
+const getSubprocessError = (error, {exitCode, signalCode}, state) => Object.assign(
+	error?.message?.startsWith('Command ')
+		? error
+		: new Error(`Command failed: ${state.command}`, {cause: error}),
+	// `exitCode` can be a negative number (`errno`) when the `error` event is emitted on the `instance`
+	exitCode >= 1 ? {exitCode} : {},
+	signalCode ? {signalName: signalCode} : {},
+	state,
+);

source/result.js

@@ -1,66 +1,27 @@
-import {once, on} from 'node:events';
 import process from 'node:process';
 
-export const getResult = async (nodeChildProcess, {input}, context) => {
-	const instance = await nodeChildProcess;
-	if (input !== undefined) {
-		instance.stdin.end(input);
-	}
-
-	const onClose = once(instance, 'close');
-
+export const getResult = async (picoPromise, nodeChildProcess, context, options) => {
 	try {
-		await Promise.race([
-			onClose,
-			...instance.stdio.filter(Boolean).map(stream => onStreamError(stream)),
-		]);
-		checkFailure(context, getErrorOutput(instance));
-		return getOutputs(context);
+		const {picoSubprocess} = await picoPromise;
+		const [result] = await Promise.all([picoSubprocess, nodeChildProcess, handleInput(picoSubprocess, options)]);
+		return updateResult(result, context);
 	} catch (error) {
-		await Promise.allSettled([onClose]);
-		throw getResultError(error, instance, context);
-	}
-};
-
-const onStreamError = async stream => {
-	for await (const [error] of on(stream, 'error')) {
-		// Ignore errors that are due to closing errors when the subprocesses exit normally, or due to piping
-		if (!['ERR_STREAM_PREMATURE_CLOSE', 'EPIPE'].includes(error?.code)) {
-			throw error;
-		}
+		error.message = error.message.replaceAll(error.command, context.command);
+		throw updateResult(error, context);
 	}
 };
 
-const checkFailure = ({command}, {exitCode, signalName}) => {
-	if (signalName !== undefined) {
-		throw new Error(`Command was terminated with ${signalName}: ${command}`);
-	}
-
-	if (exitCode !== undefined) {
-		throw new Error(`Command failed with exit code ${exitCode}: ${command}`);
+const handleInput = async ({nodeChildProcess}, {input}) => {
+	if (input !== undefined) {
+		const {stdin} = await nodeChildProcess;
+		stdin.end(input);
 	}
 };
 
-export const getResultError = (error, instance, context) => Object.assign(
-	getErrorInstance(error, context),
-	getErrorOutput(instance),
-	getOutputs(context),
-);
-
-const getErrorInstance = (error, {command}) => error?.message.startsWith('Command ')
-	? error
-	: new Error(`Command failed: ${command}`, {cause: error});
-
-const getErrorOutput = ({exitCode, signalCode}) => ({
-	// `exitCode` can be a negative number (`errno`) when the `error` event is emitted on the `instance`
-	...(exitCode < 1 ? {} : {exitCode}),
-	...(signalCode === null ? {} : {signalName: signalCode}),
-});
-
-const getOutputs = ({state: {stdout, stderr, output}, command, start}) => ({
-	stdout: getOutput(stdout),
-	stderr: getOutput(stderr),
-	output: getOutput(output),
+const updateResult = (result, {command, start}) => Object.assign(result, {
+	stdout: getOutput(result.stdout),
+	stderr: getOutput(result.stderr),
+	output: getOutput(result.output),
 	command,
 	durationMs: Number(process.hrtime.bigint() - start) / 1e6,
 });

source/spawn.js

@@ -1,43 +1,16 @@
-import {spawn} from 'node:child_process';
-import {once} from 'node:events';
 import process from 'node:process';
 import {applyForceShell} from './windows.js';
-import {getResultError} from './result.js';
 
-export const spawnSubprocess = async (file, commandArguments, options, context) => {
-	try {
-		// When running `node`, keep the current Node version and CLI flags.
-		// Not applied with file paths to `.../node` since those indicate a clear intent to use a specific Node version.
-		// Does not work with shebangs, but those don't work cross-platform anyway.
-		[file, commandArguments] = ['node', 'node.exe'].includes(file.toLowerCase())
-			? [process.execPath, [...process.execArgv.filter(flag => !flag.startsWith('--inspect')), ...commandArguments]]
-			: [file, commandArguments];
+export const handleArguments = async (file, commandArguments, options, context) => {
+	// When running `node`, keep the current Node version and CLI flags.
+	// Not applied with file paths to `.../node` since those indicate a clear intent to use a specific Node version.
+	// This also provides a way to opting out, e.g. using `process.execPath` instead of `node` to discard current CLI flags.
+	// Does not work with shebangs, but those don't work cross-platform anyway.
+	[file, commandArguments] = ['node', 'node.exe'].includes(file.toLowerCase())
+		? [process.execPath, [...process.execArgv.filter(flag => !flag.startsWith('--inspect')), ...commandArguments]]
+		: [file, commandArguments];
 
-		const instance = spawn(...await applyForceShell(file, commandArguments, options));
-		bufferOutput(instance.stdout, context, 'stdout');
-		bufferOutput(instance.stderr, context, 'stderr');
-
-		// The `error` event is caught by `once(instance, 'spawn')` and `once(instance, 'close')`.
-		// But it creates an uncaught exception if it happens exactly one tick after 'spawn'.
-		// This prevents that.
-		instance.once('error', () => {});
-
-		await once(instance, 'spawn');
-		return instance;
-	} catch (error) {
-		throw getResultError(error, {}, context);
-	}
-};
-
-const bufferOutput = (stream, {state}, streamName) => {
-	if (stream) {
-		stream.setEncoding('utf8');
-		if (!state.isIterating) {
-			state.isIterating = false;
-			stream.on('data', chunk => {
-				state[streamName] += chunk;
-				state.output += chunk;
-			});
-		}
-	}
+	[file, commandArguments, options] = await applyForceShell(file, commandArguments, options);
+	context.isIterating ??= false;
+	return [file, commandArguments, {...options, buffer: !context.isIterating}];
 };