commit 3f0a2e0b5bfa15936d21748459570cab782ed0ed
Author: Nhân <hi@imnhan.com>
Date:   Sun Jul 16 23:49:54 2023 +0700

    support showing arbitrary errors in html

diff --git a/livereload/error.go b/livereload/error.go
index b8ed95d..ac650db 100644
--- a/livereload/error.go
+++ b/livereload/error.go
@@ -18,9 +18,21 @@ type htmlErr interface {
 	Html() template.HTML
 }
 
-func serveError(w http.ResponseWriter, r *http.Request, err htmlErr) {
+func serveError(w http.ResponseWriter, r *http.Request, err error) {
 	var buf bytes.Buffer
-	errTmpl.Execute(&buf, err)
+	_, ok := err.(htmlErr)
+	if ok {
+		errTmpl.Execute(&buf, err)
+	} else {
+		// Shim for errors that don't support HTML output
+		errTmpl.Execute(&buf, struct {
+			Error string
+			Html  template.HTML
+		}{
+			Error: err.Error(),
+			Html:  template.HTML(err.Error()),
+		})
+	}
 	body := withLiveReload(buf.Bytes())
 	w.Write(body)
 }
diff --git a/livereload/livereload.go b/livereload/livereload.go
index b51105a..4eb7615 100644
--- a/livereload/livereload.go
+++ b/livereload/livereload.go
@@ -86,7 +86,7 @@ func Middleware(mux *http.ServeMux, root string, fsys writablefs.FS, f http.Hand
 		err = state.err
 		state.errMut.RUnlock()
 		if err != nil {
-			serveError(w, r, err.(htmlErr))
+			serveError(w, r, err)
 			return
 		}