Add filter option to getOneMessage()

docs/api.md

@@ -103,8 +103,9 @@ This requires the [`ipc`](#optionsipc) option to be `true`. The [type](ipc.md#me
 
 [More info.](ipc.md#exchanging-messages)
 
-### getOneMessage()
+### getOneMessage(getOneMessageOptions?)
 
+_getOneMessageOptions_: [`GetOneMessageOptions`](#getonemessageoptions)\
 _Returns_: [`Promise<Message>`](ipc.md#message-type)
 
 Receive a single `message` from the parent process.
@@ -113,6 +114,18 @@ This requires the [`ipc`](#optionsipc) option to be `true`. The [type](ipc.md#me
 
 [More info.](ipc.md#exchanging-messages)
 
+#### getOneMessageOptions
+
+_Type_: `object`
+
+#### getOneMessageOptions.filter
+
+_Type_: [`(Message) => boolean`](ipc.md#message-type)
+
+Ignore any `message` that returns `false`.
+
+[More info.](ipc.md#filter-messages)
+
 ### getEachMessage()
 
 _Returns_: [`AsyncIterable<Message>`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#the_async_iterator_and_async_iterable_protocols)
@@ -259,8 +272,9 @@ This requires the [`ipc`](#optionsipc) option to be `true`. The [type](ipc.md#me
 
 [More info.](ipc.md#exchanging-messages)
 
-### subprocess.getOneMessage()
+### subprocess.getOneMessage(getOneMessageOptions?)
 
+_getOneMessageOptions_: [`GetOneMessageOptions`](#getonemessageoptions)\
 _Returns_: [`Promise<Message>`](ipc.md#message-type)
 
 Receive a single `message` from the subprocess.
@@ -900,7 +914,7 @@ By default, this applies to both `stdout` and `stderr`, but [different values ca
 _Type:_ `boolean`\
 _Default:_ `true` if either the [`node`](#optionsnode) option or the [`ipcInput`](#optionsipcinput) is set, `false` otherwise
 
-Enables exchanging messages with the subprocess using [`subprocess.sendMessage(message)`](#subprocesssendmessagemessage), [`subprocess.getOneMessage()`](#subprocessgetonemessage) and [`subprocess.getEachMessage()`](#subprocessgeteachmessage).
+Enables exchanging messages with the subprocess using [`subprocess.sendMessage(message)`](#subprocesssendmessagemessage), [`subprocess.getOneMessage()`](#subprocessgetonemessagegetonemessageoptions) and [`subprocess.getEachMessage()`](#subprocessgeteachmessage).
 
 The subprocess must be a Node.js file.
 

docs/execution.md

@@ -126,7 +126,7 @@ Synchronous execution is generally discouraged as it holds the CPU and prevents
 - Signal termination: [`subprocess.kill()`](api.md#subprocesskillerror), [`subprocess.pid`](api.md#subprocesspid), [`cleanup`](api.md#optionscleanup) option, [`cancelSignal`](api.md#optionscancelsignal) option, [`forceKillAfterDelay`](api.md#optionsforcekillafterdelay) option.
 - Piping multiple subprocesses: [`subprocess.pipe()`](api.md#subprocesspipefile-arguments-options).
 - [`subprocess.iterable()`](lines.md#progressive-splitting).
-- [IPC](ipc.md): [`sendMessage()`](api.md#sendmessagemessage), [`getOneMessage()`](api.md#getonemessage), [`getEachMessage()`](api.md#geteachmessage), [`result.ipcOutput`](output.md#any-output-type), [`ipc`](api.md#optionsipc) option, [`serialization`](api.md#optionsserialization) option, [`ipcInput`](input.md#any-input-type) option.
+- [IPC](ipc.md): [`sendMessage()`](api.md#sendmessagemessage), [`getOneMessage()`](api.md#getonemessagegetonemessageoptions), [`getEachMessage()`](api.md#geteachmessage), [`result.ipcOutput`](output.md#any-output-type), [`ipc`](api.md#optionsipc) option, [`serialization`](api.md#optionsserialization) option, [`ipcInput`](input.md#any-input-type) option.
 - [`result.all`](api.md#resultall) is not interleaved.
 - [`detached`](api.md#optionsdetached) option.
 - The [`maxBuffer`](api.md#optionsmaxbuffer) option is always measured in bytes, not in characters, [lines](api.md#optionslines) nor [objects](transform.md#object-mode). Also, it ignores transforms and the [`encoding`](api.md#optionsencoding) option.

docs/input.md

@@ -92,7 +92,7 @@ await execa({stdin: 'inherit'})`npm run scaffold`;
 
 ## Any input type
 
-If the subprocess [uses Node.js](node.md), [almost any type](ipc.md#message-type) can be passed to the subprocess using the [`ipcInput`](ipc.md#send-an-initial-message) option. The subprocess retrieves that input using [`getOneMessage()`](api.md#getonemessage).
+If the subprocess [uses Node.js](node.md), [almost any type](ipc.md#message-type) can be passed to the subprocess using the [`ipcInput`](ipc.md#send-an-initial-message) option. The subprocess retrieves that input using [`getOneMessage()`](api.md#getonemessagegetonemessageoptions).
 
 ```js
 // main.js

docs/ipc.md

@@ -12,7 +12,7 @@ When the [`ipc`](api.md#optionsipc) option is `true`, the current process and su
 
 The `ipc` option defaults to `true` when using [`execaNode()`](node.md#run-nodejs-files) or the [`node`](node.md#run-nodejs-files) option.
 
-The current process sends messages with [`subprocess.sendMessage(message)`](api.md#subprocesssendmessagemessage) and receives them with [`subprocess.getOneMessage()`](api.md#subprocessgetonemessage). The subprocess uses [`sendMessage(message)`](api.md#sendmessagemessage) and [`getOneMessage()`](api.md#getonemessage) instead.
+The current process sends messages with [`subprocess.sendMessage(message)`](api.md#subprocesssendmessagemessage) and receives them with [`subprocess.getOneMessage()`](api.md#subprocessgetonemessagegetonemessageoptions). The subprocess uses [`sendMessage(message)`](api.md#sendmessagemessage) and [`getOneMessage()`](api.md#getonemessagegetonemessageoptions) instead.
 
 ```js
 // parent.js
@@ -33,7 +33,7 @@ console.log(await getOneMessage()); // 'Hello from parent'
 
 ## Listening to messages
 
-[`subprocess.getOneMessage()`](api.md#subprocessgetonemessage) and [`getOneMessage()`](api.md#getonemessage) read a single message. To listen to multiple messages in a row, [`subprocess.getEachMessage()`](api.md#subprocessgeteachmessage) and [`getEachMessage()`](api.md#geteachmessage) should be used instead.
+[`subprocess.getOneMessage()`](api.md#subprocessgetonemessagegetonemessageoptions) and [`getOneMessage()`](api.md#getonemessagegetonemessageoptions) read a single message. To listen to multiple messages in a row, [`subprocess.getEachMessage()`](api.md#subprocessgeteachmessage) and [`getEachMessage()`](api.md#geteachmessage) should be used instead.
 
 [`subprocess.getEachMessage()`](api.md#subprocessgeteachmessage) waits for the subprocess to end (even when using [`break`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/break) or [`return`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/return)). It throws if the subprocess [fails](api.md#result). This means you do not need to `await` the subprocess' [promise](execution.md#result).
 
@@ -67,9 +67,29 @@ for await (const message of getEachMessage()) {
 }
 ```
 
+## Filter messages
+
+```js
+import {getOneMessage} from 'execa';
+
+const startMessage = await getOneMessage({
+	filter: message => message.type === 'start',
+});
+```
+
+```js
+import {getEachMessage} from 'execa';
+
+for await (const message of getEachMessage()) {
+	if (message.type === 'start') {
+		// ...
+	}
+}
+```
+
 ## Retrieve all messages
 
-The [`result.ipcOutput`](api.md#resultipcoutput) array contains all the messages sent by the subprocess. In many situations, this is simpler than using [`subprocess.getOneMessage()`](api.md#subprocessgetonemessage) and [`subprocess.getEachMessage()`](api.md#subprocessgeteachmessage).
+The [`result.ipcOutput`](api.md#resultipcoutput) array contains all the messages sent by the subprocess. In many situations, this is simpler than using [`subprocess.getOneMessage()`](api.md#subprocessgetonemessagegetonemessageoptions) and [`subprocess.getEachMessage()`](api.md#subprocessgeteachmessage).
 
 ```js
 // main.js
@@ -118,6 +138,8 @@ By default, messages are serialized using [`structuredClone()`](https://develope
 To limit messages to JSON instead, the [`serialization`](api.md#optionsserialization) option can be set to `'json'`.
 
 ```js
+import {execaNode} from 'execa';
+
 const subprocess = execaNode({serialization: 'json'})`child.js`;
 ```
 

lib/ipc/get-one.js

@@ -1,4 +1,4 @@
-import {once} from 'node:events';
+import {once, on} from 'node:events';
 import {
 	validateIpcOption,
 	validateConnection,
@@ -7,27 +7,31 @@ import {
 } from './validation.js';
 
 // Like `[sub]process.once('message')` but promise-based
-export const getOneMessage = ({anyProcess, isSubprocess, ipc}) => {
+export const getOneMessage = ({anyProcess, isSubprocess, ipc}, {filter} = {}) => {
 	const methodName = 'getOneMessage';
 	validateIpcOption(methodName, isSubprocess, ipc);
 	validateConnection(methodName, isSubprocess, anyProcess.channel !== null);
 
-	return onceMessage(anyProcess, isSubprocess, methodName);
+	return onceMessage({
+		anyProcess,
+		isSubprocess,
+		methodName,
+		filter,
+	});
 };
 
-const onceMessage = async (anyProcess, isSubprocess, methodName) => {
+const onceMessage = async ({anyProcess, isSubprocess, methodName, filter}) => {
 	const controller = new AbortController();
 	try {
-		const [message] = await Promise.race([
-			once(anyProcess, 'message', {signal: controller.signal}),
+		return await Promise.race([
+			getMessage(anyProcess, filter, controller),
 			throwOnDisconnect({
 				anyProcess,
 				isSubprocess,
 				methodName,
 				controller,
 			}),
 		]);
-		return message;
 	} catch (error) {
 		disconnect(anyProcess);
 		throw error;
@@ -36,6 +40,19 @@ const onceMessage = async (anyProcess, isSubprocess, methodName) => {
 	}
 };
 
+const getMessage = async (anyProcess, filter, {signal}) => {
+	if (filter === undefined) {
+		const [message] = await once(anyProcess, 'message', {signal});
+		return message;
+	}
+
+	for await (const [message] of on(anyProcess, 'message', {signal})) {
+		if (filter(message)) {
+			return message;
+		}
+	}
+};
+
 const throwOnDisconnect = async ({anyProcess, isSubprocess, methodName, controller: {signal}}) => {
 	await once(anyProcess, 'disconnect', {signal});
 	throwOnEarlyDisconnect(methodName, isSubprocess);

test-d/ipc/get-each.test-d.ts

@@ -6,12 +6,6 @@ import {
 	type Options,
 } from '../../index.js';
 
-for await (const message of getEachMessage()) {
-	expectType<Message>(message);
-}
-
-expectError(getEachMessage(''));
-
 const subprocess = execa('test', {ipc: true});
 
 for await (const message of subprocess.getEachMessage()) {
@@ -22,7 +16,12 @@ for await (const message of execa('test', {ipc: true, serialization: 'json'}).ge
 	expectType<Message<'json'>>(message);
 }
 
+for await (const message of getEachMessage()) {
+	expectType<Message>(message);
+}
+
 expectError(subprocess.getEachMessage(''));
+expectError(getEachMessage(''));
 
 execa('test', {ipcInput: ''}).getEachMessage();
 execa('test', {ipcInput: '' as Message}).getEachMessage();

test-d/ipc/get-one.test-d.ts

@@ -6,14 +6,14 @@ import {
 	type Options,
 } from '../../index.js';
 
-expectType<Promise<Message>>(getOneMessage());
-expectError(await getOneMessage(''));
-
 const subprocess = execa('test', {ipc: true});
-expectType<Message<'advanced'>>(await subprocess.getOneMessage());
-expectType<Message<'json'>>(await execa('test', {ipc: true, serialization: 'json'}).getOneMessage());
+expectType<Promise<Message<'advanced'>>>(subprocess.getOneMessage());
+const jsonSubprocess = execa('test', {ipc: true, serialization: 'json'});
+expectType<Promise<Message<'json'>>>(jsonSubprocess.getOneMessage());
+expectType<Promise<Message>>(getOneMessage());
 
 expectError(await subprocess.getOneMessage(''));
+expectError(await getOneMessage(''));
 
 await execa('test', {ipcInput: ''}).getOneMessage();
 await execa('test', {ipcInput: '' as Message}).getOneMessage();
@@ -26,3 +26,30 @@ expectType<undefined>(execa('test', {}).getOneMessage);
 expectType<undefined>(execa('test', {ipc: false}).getOneMessage);
 expectType<undefined>(execa('test', {ipcInput: undefined}).getOneMessage);
 expectType<undefined>(execa('test', {ipc: false, ipcInput: ''}).getOneMessage);
+
+await subprocess.getOneMessage({filter: undefined} as const);
+await subprocess.getOneMessage({filter: (message: Message<'advanced'>) => true} as const);
+await jsonSubprocess.getOneMessage({filter: (message: Message<'json'>) => true} as const);
+await jsonSubprocess.getOneMessage({filter: (message: Message<'advanced'>) => true} as const);
+await subprocess.getOneMessage({filter: (message: Message<'advanced'> | bigint) => true} as const);
+await subprocess.getOneMessage({filter: () => true} as const);
+expectError(await subprocess.getOneMessage({filter: (message: Message<'advanced'>) => ''} as const));
+// eslint-disable-next-line @typescript-eslint/no-empty-function
+expectError(await subprocess.getOneMessage({filter(message: Message<'advanced'>) {}} as const));
+expectError(await subprocess.getOneMessage({filter: (message: Message<'json'>) => true} as const));
+expectError(await subprocess.getOneMessage({filter: (message: '') => true} as const));
+expectError(await subprocess.getOneMessage({filter: true} as const));
+expectError(await subprocess.getOneMessage({unknownOption: true} as const));
+
+await getOneMessage({filter: undefined} as const);
+await getOneMessage({filter: (message: Message) => true} as const);
+await getOneMessage({filter: (message: Message<'advanced'>) => true} as const);
+await getOneMessage({filter: (message: Message | bigint) => true} as const);
+await getOneMessage({filter: () => true} as const);
+expectError(await getOneMessage({filter: (message: Message) => ''} as const));
+// eslint-disable-next-line @typescript-eslint/no-empty-function
+expectError(await getOneMessage({filter(message: Message) {}} as const));
+expectError(await getOneMessage({filter: (message: Message<'json'>) => true} as const));
+expectError(await getOneMessage({filter: (message: '') => true} as const));
+expectError(await getOneMessage({filter: true} as const));
+expectError(await getOneMessage({unknownOption: true} as const));

test-d/ipc/send.test-d.ts

@@ -6,18 +6,19 @@ import {
 	type Options,
 } from '../../index.js';
 
+const subprocess = execa('test', {ipc: true});
+expectType<void>(await subprocess.sendMessage(''));
 expectType<Promise<void>>(sendMessage(''));
 
+expectError(await subprocess.sendMessage());
 expectError(await sendMessage());
+expectError(await subprocess.sendMessage(undefined));
 expectError(await sendMessage(undefined));
+expectError(await subprocess.sendMessage(0n));
 expectError(await sendMessage(0n));
+expectError(await subprocess.sendMessage(Symbol('test')));
 expectError(await sendMessage(Symbol('test')));
 
-const subprocess = execa('test', {ipc: true});
-expectType<void>(await subprocess.sendMessage(''));
-
-expectError(await subprocess.sendMessage());
-
 await execa('test', {ipcInput: ''}).sendMessage('');
 await execa('test', {ipcInput: '' as Message}).sendMessage('');
 await execa('test', {} as Options).sendMessage?.('');

test/fixtures/ipc-echo-filter.js

@@ -0,0 +1,5 @@
+#!/usr/bin/env node
+import {sendMessage, getOneMessage} from '../../index.js';
+import {foobarArray} from '../helpers/input.js';
+
+await sendMessage(await getOneMessage(({filter: message => message === foobarArray[1]})));

test/fixtures/ipc-echo-twice-filter.js

@@ -0,0 +1,8 @@
+#!/usr/bin/env node
+import {sendMessage, getOneMessage} from '../../index.js';
+import {alwaysPass} from '../helpers/ipc.js';
+
+const message = await getOneMessage({filter: alwaysPass});
+const secondMessagePromise = getOneMessage({filter: alwaysPass});
+await sendMessage(message);
+await sendMessage(await secondMessagePromise);

test/fixtures/ipc-process-error-filter.js

@@ -0,0 +1,11 @@
+#!/usr/bin/env node
+import process from 'node:process';
+import {getOneMessage} from '../../index.js';
+import {foobarString} from '../helpers/input.js';
+import {alwaysPass} from '../helpers/ipc.js';
+
+const cause = new Error(foobarString);
+await Promise.all([
+	getOneMessage({filter: alwaysPass}),
+	process.emit('error', cause),
+]);

test/helpers/ipc.js

@@ -7,3 +7,5 @@ export const iterateAllMessages = async subprocess => {
 
 	return messages;
 };
+
+export const alwaysPass = () => true;

test/ipc/buffer-messages.js

@@ -56,3 +56,14 @@ test('Sets empty error.ipcOutput, sync', t => {
 	const {ipcOutput} = t.throws(() => execaSync('fail.js'));
 	t.deepEqual(ipcOutput, []);
 });
+
+test('"error" event interrupts result.ipcOutput', async t => {
+	const subprocess = execa('ipc-echo-twice.js', {ipcInput: foobarString});
+	t.is(await subprocess.getOneMessage(), foobarString);
+
+	const cause = new Error(foobarString);
+	subprocess.emit('error', cause);
+	const error = await t.throwsAsync(subprocess);
+	t.is(error.cause, cause);
+	t.deepEqual(error.ipcOutput, [foobarString]);
+});