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node_modules/execa/lib/ipc/outgoing.js

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+import {createDeferred} from '../utils/deferred.js';
+import {getFdSpecificValue} from '../arguments/specific.js';
+import {SUBPROCESS_OPTIONS} from '../arguments/fd-options.js';
+import {validateStrictDeadlock} from './strict.js';
+
+// When `sendMessage()` is ongoing, any `message` being received waits before being emitted.
+// This allows calling one or multiple `await sendMessage()` followed by `await getOneMessage()`/`await getEachMessage()`.
+// Without running into a race condition when the other process sends a response too fast, before the current process set up a listener.
+export const startSendMessage = (anyProcess, wrappedMessage, strict) => {
+	if (!OUTGOING_MESSAGES.has(anyProcess)) {
+		OUTGOING_MESSAGES.set(anyProcess, new Set());
+	}
+
+	const outgoingMessages = OUTGOING_MESSAGES.get(anyProcess);
+	const onMessageSent = createDeferred();
+	const id = strict ? wrappedMessage.id : undefined;
+	const outgoingMessage = {onMessageSent, id};
+	outgoingMessages.add(outgoingMessage);
+	return {outgoingMessages, outgoingMessage};
+};
+
+export const endSendMessage = ({outgoingMessages, outgoingMessage}) => {
+	outgoingMessages.delete(outgoingMessage);
+	outgoingMessage.onMessageSent.resolve();
+};
+
+// Await while `sendMessage()` is ongoing, unless there is already a `message` listener
+export const waitForOutgoingMessages = async (anyProcess, ipcEmitter, wrappedMessage) => {
+	while (!hasMessageListeners(anyProcess, ipcEmitter) && OUTGOING_MESSAGES.get(anyProcess)?.size > 0) {
+		const outgoingMessages = [...OUTGOING_MESSAGES.get(anyProcess)];
+		validateStrictDeadlock(outgoingMessages, wrappedMessage);
+		// eslint-disable-next-line no-await-in-loop
+		await Promise.all(outgoingMessages.map(({onMessageSent}) => onMessageSent));
+	}
+};
+
+const OUTGOING_MESSAGES = new WeakMap();
+
+// Whether any `message` listener is setup
+export const hasMessageListeners = (anyProcess, ipcEmitter) => ipcEmitter.listenerCount('message') > getMinListenerCount(anyProcess);
+
+// When `buffer` is `false`, we set up a `message` listener that should be ignored.
+// That listener is only meant to intercept `strict` acknowledgement responses.
+const getMinListenerCount = anyProcess => SUBPROCESS_OPTIONS.has(anyProcess)
+	&& !getFdSpecificValue(SUBPROCESS_OPTIONS.get(anyProcess).options.buffer, 'ipc')
+	? 1
+	: 0;