Polyfill WebSocket on Node

frontend/sync-client/package.json

@@ -23,6 +23,7 @@
 		"@types/jest": "^29.5.14",
 		"@types/node": "^22.13.10",
 		"jest": "^29.7.0",
+		"sync_lib": "file:../../backend/sync_lib/pkg",
 		"ts-jest": "^29.2.6",
 		"ts-loader": "^9.5.2",
 		"tslib": "2.8.1",
@@ -30,6 +31,6 @@
 		"webpack": "^5.98.0",
 		"webpack-cli": "^6.0.1",
 		"webpack-merge": "^6.0.1",
-		"sync_lib": "file:../../backend/sync_lib/pkg"
+		"ws": "^8.18.1"
 	}
-}
+}

frontend/sync-client/src/sync-operations/syncer.ts

@@ -249,6 +249,15 @@ export class Syncer {
 		const wsUri = new URL(settings.remoteUri);
 		wsUri.protocol = wsUri.protocol === "https" ? "wss" : "ws";
 		wsUri.pathname = `/vaults/${settings.vaultName}/ws`;
+
+		if (
+			typeof globalThis !== "undefined" &&
+			typeof globalThis.WebSocket === "undefined"
+		) {
+			// polyfill for WebSocket in Node.js
+			globalThis.WebSocket = require("ws");
+		}
+
 		this.applyRemoteChangesWebSocket = new WebSocket(wsUri);
 
 		this.applyRemoteChangesWebSocket.onmessage = (event): void =>

frontend/sync-client/webpack.config.js

@@ -20,7 +20,7 @@ const common = {
 		minimize: false
 	},
 	resolve: {
-		extensions: [".ts"],
+		extensions: [".ts", ".js"],
 		alias: {
 			root: __dirname,
 			src: path.resolve(__dirname, "src")
@@ -42,6 +42,11 @@ module.exports = [
 				type: "umd"
 			},
 			globalObject: "this"
+		},
+		resolve: {
+			fallback: {
+				ws: false // Exclude `ws` from the browser bundle
+			}
 		}
 	}),
 	merge(common, {
@@ -50,6 +55,10 @@ module.exports = [
 			path: path.resolve(__dirname, "dist"),
 			filename: "sync-client.node.js",
 			libraryTarget: "commonjs2"
+		},
+		externals: {
+			bufferutil: "bufferutil",
+			"utf-8-validate": "utf-8-validate" // required for ws: https://github.com/websockets/ws/issues/2245#issuecomment-2250318733
 		}
 	})
 ];

frontend/test-client/package.json

@@ -18,6 +18,7 @@
 		"typescript": "5.8.2",
 		"uuid": "^11.1.0",
 		"webpack": "^5.98.0",
-		"webpack-cli": "^6.0.1"
+		"webpack-cli": "^6.0.1",
+		"bufferutil": "^4.0.9"
 	}
-}
+}