cmd/tsconnect: output errors to the JS console too

We were just outputting them to the terminal, but that's hard to debug
because we immediately tear down the terminal when getting an error.

Signed-off-by: Mihai Parparita <mihai@tailscale.com>

cmd/tsconnect/src/lib/ssh.ts

@@ -27,26 +27,39 @@ export function runSSHSession(
 
   term.focus()
 
-  const sshSession = ipn.ssh(def.hostname, def.username, {
+  let resizeObserver: ResizeObserver | undefined
-    writeFn: (input) => term.write(input),
+  let handleBeforeUnload: ((e: BeforeUnloadEvent) => void) | undefined
-    setReadFn: (hook) => (onDataHook = hook),
+
+  const sshSession = ipn.ssh(def.hostname + "2", def.username, {
+    writeFn(input) {
+      term.write(input)
+    },
+    writeErrorFn(err) {
+      console.error(err)
+      term.write(err)
+    },
+    setReadFn(hook) {
+      onDataHook = hook
+    },
     rows: term.rows,
     cols: term.cols,
-    onDone: () => {
+    onDone() {
-      resizeObserver.disconnect()
+      resizeObserver?.disconnect()
       term.dispose()
-      window.removeEventListener("beforeunload", handleBeforeUnload)
+      if (handleBeforeUnload) {
+        window.removeEventListener("beforeunload", handleBeforeUnload)
+      }
       onDone()
     },
   })
 
   // Make terminal and SSH session track the size of the containing DOM node.
-  const resizeObserver = new ResizeObserver(() => fitAddon.fit())
+  resizeObserver = new ResizeObserver(() => fitAddon.fit())
   resizeObserver.observe(termContainerNode)
   term.onResize(({ rows, cols }) => sshSession.resize(rows, cols))
 
   // Close the session if the user closes the window without an explicit
   // exit.
-  const handleBeforeUnload = () => sshSession.close()
+  handleBeforeUnload = () => sshSession.close()
   window.addEventListener("beforeunload", handleBeforeUnload)
 }

cmd/tsconnect/src/types/wasm_js.d.ts

@@ -19,6 +19,7 @@ declare global {
       username: string,
       termConfig: {
         writeFn: (data: string) => void
+        writeErrorFn: (err: string) => void
         setReadFn: (readFn: (data: string) => void) => void
         rows: number
         cols: number

cmd/tsconnect/wasm/wasm_js.go

@@ -347,6 +347,7 @@ type jsSSHSession struct {
 
 func (s *jsSSHSession) Run() {
 	writeFn := s.termConfig.Get("writeFn")
+	writeErrorFn := s.termConfig.Get("writeErrorFn")
 	setReadFn := s.termConfig.Get("setReadFn")
 	rows := s.termConfig.Get("rows").Int()
 	cols := s.termConfig.Get("cols").Int()
@@ -357,7 +358,7 @@ func (s *jsSSHSession) Run() {
 		writeFn.Invoke(s)
 	}
 	writeError := func(label string, err error) {
-		write(fmt.Sprintf("%s Error: %v\r\n", label, err))
+		writeErrorFn.Invoke(fmt.Sprintf("%s Error: %v\r\n", label, err))
 	}
 
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)