Merge pull request #881 from posit-dev/mm-fallback-handler

Add fallback handler for 404s

internal/services/middleware/404_service.go

@@ -0,0 +1,61 @@
+package middleware
+
+// Copyright (C) 2023 by Posit Software, PBC.
+
+import "net/http"
+
+type notFoundWriter struct {
+	writer     http.ResponseWriter
+	header     http.Header
+	StatusCode int
+}
+
+func newNotFoundWriter(w http.ResponseWriter) *notFoundWriter {
+	return &notFoundWriter{
+		writer: w,
+		header: http.Header{},
+	}
+}
+
+func (w *notFoundWriter) Header() http.Header {
+	// Capture the header sent by the underlying handler,
+	// and decide later whether to send it.
+	return w.header
+}
+
+func (w *notFoundWriter) Write(data []byte) (int, error) {
+	if w.StatusCode != http.StatusNotFound {
+		// We have a valid response, send it.
+		return w.writer.Write(data)
+	} else {
+		// Eat this response and we'll serve up a better one
+		return len(data), nil
+	}
+}
+
+func (w *notFoundWriter) WriteHeader(statusCode int) {
+	w.StatusCode = statusCode
+	if statusCode != http.StatusNotFound {
+		// Valid response from the underlying handler.
+		// Respond with the headers that handler provided.
+		realHeader := w.writer.Header()
+		for k, v := range w.header {
+			realHeader[k] = v
+		}
+		w.writer.WriteHeader(statusCode)
+	}
+}
+
+func ServeIndexOn404(h http.Handler, location string) http.HandlerFunc {
+	return func(w http.ResponseWriter, req *http.Request) {
+		writer := newNotFoundWriter(w)
+		h.ServeHTTP(writer, req)
+
+		if writer.StatusCode == http.StatusNotFound {
+			// Serve the index.html page and let the frontend handle routing
+			req.URL.Path = "/"
+			req.URL.RawPath = "/"
+			h.ServeHTTP(w, req)
+		}
+	}
+}

internal/services/ui/ui_service.go

@@ -103,13 +103,17 @@ func RouterHandlerFunc(base util.Path, lister accounts.AccountList, log logging.
 	r.Handle(ToPath("deployments", "{name}"), api.DeleteDeploymentHandlerFunc(base, log)).
 		Methods(http.MethodDelete)
 
-	// GET /
+	// Handle any frontend paths that leak out (for example, on a refresh)
+	// by redirecting to the SPA at "/".
+
+	// GET /<anything>
+	// Serves static files from /web/dist.
+	fileHandler := middleware.InsertPrefix(web.Handler, web.Prefix)
 	r.PathPrefix("/").
-		Handler(middleware.InsertPrefix(web.Handler, web.Prefix)).
+		Handler(middleware.ServeIndexOn404(fileHandler, "/")).
 		Methods("GET")
 
 	c := cors.AllowAll().Handler(r)
-
 	return c.ServeHTTP
 }
 

web/vite.config.ts

@@ -8,7 +8,7 @@ import { quasar, transformAssetUrls } from '@quasar/vite-plugin';
 // https://vitejs.dev/config/
 // eslint-disable-next-line no-restricted-syntax
 export default defineConfig({
-  base: './',
+  base: '/',
   build: {
     rollupOptions: {
       output: {