Lock file on save and read (#824)

Fix #794

src/Utils/use-multi-file-auth-state.ts

@@ -1,3 +1,4 @@
+import AsyncLock from 'async-lock'
 import { mkdir, readFile, stat, unlink, writeFile } from 'fs/promises'
 import { join } from 'path'
 import { proto } from '../../WAProto'
@@ -5,6 +6,13 @@ import { AuthenticationCreds, AuthenticationState, SignalDataTypeMap } from '../
 import { initAuthCreds } from './auth-utils'
 import { BufferJSON } from './generics'
 
+// We need to lock files due to the fact that we are using async functions to read and write files
+// https://github.com/WhiskeySockets/Baileys/issues/794
+// https://github.com/nodejs/node/issues/26338
+// Default pending is 1000, set it to infinity
+// https://github.com/rogierschouten/async-lock/issues/63
+const fileLock = new AsyncLock({ maxPending: Infinity })
+
 /**
  * stores the full authentication state in a single folder.
  * Far more efficient than singlefileauthstate
@@ -15,12 +23,20 @@ import { BufferJSON } from './generics'
 export const useMultiFileAuthState = async(folder: string): Promise<{ state: AuthenticationState, saveCreds: () => Promise<void> }> => {
 
 	const writeData = (data: any, file: string) => {
-		return writeFile(join(folder, fixFileName(file)!), JSON.stringify(data, BufferJSON.replacer))
+		const filePath = join(folder, fixFileName(file)!)
+		return fileLock.acquire(
+			filePath,
+			() => writeFile(join(filePath), JSON.stringify(data, BufferJSON.replacer))
+		)
 	}
 
 	const readData = async(file: string) => {
 		try {
-			const data = await readFile(join(folder, fixFileName(file)!), { encoding: 'utf-8' })
+			const filePath = join(folder, fixFileName(file)!)
+			const data = await fileLock.acquire(
+				filePath,
+				() => readFile(filePath, { encoding: 'utf-8' })
+			)
 			return JSON.parse(data, BufferJSON.reviver)
 		} catch(error) {
 			return null
@@ -29,7 +45,11 @@ export const useMultiFileAuthState = async(folder: string): Promise<{ state: Aut
 
 	const removeData = async(file: string) => {
 		try {
-			await unlink(join(folder, fixFileName(file)!))
+			const filePath = join(folder, fixFileName(file)!)
+			await fileLock.acquire(
+				filePath,
+				() => unlink(filePath)
+			)
 		} catch{
 
 		}
@@ -87,4 +107,4 @@ export const useMultiFileAuthState = async(folder: string): Promise<{ state: Aut
 			return writeData(creds, 'creds.json')
 		}
 	}
-}
+}