lsp: Fix handling of binary websocket messages

lib/esbonio/changes/665.fix.md

@@ -0,0 +1 @@
+Fix handling of binary websocket messages in documentation previews

lib/esbonio/esbonio/sphinx_agent/static/webview.js

@@ -221,7 +221,10 @@ const showMarkers = queryParams.has("show-markers")
 const wsUrl = queryParams.get("ws");
 
 console.debug(`Connecting to '${wsUrl}'...`)
+const textDecoder = new TextDecoder()
 const socket = new WebSocket(wsUrl);
+socket.binaryType = 'arraybuffer'
+
 let connected = false
 
 function sendMessage(data) {
@@ -279,7 +282,16 @@ socket.addEventListener("open", (event) => {
 
 // Listen for messages
 socket.addEventListener("message", (event) => {
-    handle(JSON.parse(event.data))
+    let message
+
+    if (event.data instanceof ArrayBuffer) {
+        let buf = new Uint8Array(event.data)
+        message = JSON.parse(textDecoder.decode(buf))
+    } else {
+        message = JSON.parse(event.data)
+    }
+
+    handle(message)
 });
 
 function main() {