Serve Ember bootstrap HTML for all non-api requests

The backend no longer checks for an "html" in the `Accept` header.
With the exception of 3 session related routes, all paths not starting
with "/api" will be redirected to the static Ember bootstrap page.

As a result of this change all non-api requests that don't contain
"html" in the `Accept` header will now unconditionally return `200`,
rather than `404`.  In a sense, this expands the scope of rust-lang#556 to all
requests, not just those that set the header.  It also inverts the
problem described in rust-lang#788, effectively turning it into a duplicate
of rust-lang#556.

Fixes: rust-lang#163

Author: jtgeibel

src/middleware/ember_index_rewrite.rs

@@ -25,21 +25,20 @@ impl AroundMiddleware for EmberIndexRewrite {
 
 impl Handler for EmberIndexRewrite {
     fn call(&self, req: &mut dyn Request) -> Result<Response, Box<dyn Error + Send>> {
-        // If the client is requesting html, then we've only got one page so
-        // rewrite the request.
-        let wants_html = req
-            .headers()
-            .find("Accept")
-            .map(|accept| accept.iter().any(|s| s.contains("html")))
-            .unwrap_or(false);
-        // If the route starts with /api, just assume they want the API
-        // response and fall through.
-        let is_api_path = req.path().starts_with("/api");
         let handler = self.handler.as_ref().unwrap();
-        if wants_html && !is_api_path {
-            handler.call(&mut RequestProxy::rewrite_path(req, "/index.html"))
-        } else {
+        let is_backend_path = match req.path() {
+            // Special case routes used for authentication
+            "/authorize" | "/authorize_url" | "/logout" => true,
+            // Paths starting with `/api` are intended for the backend
+            path if path.starts_with("/api") => true,
+            _ => false,
+        };
+
+        if is_backend_path {
             handler.call(req)
+        } else {
+            // Serve static Ember page to bootstrap the frontend
+            handler.call(&mut RequestProxy::rewrite_path(req, "/index.html"))
         }
     }
 }

src/router.rs

@@ -108,6 +108,8 @@ pub fn build_router(app: &App) -> R404 {
     router.head("/api/v1/*path", R(Arc::clone(&api_router)));
     router.delete("/api/v1/*path", R(api_router));
 
+    // These routes are special cased in the EmberIndexRewrite middleware.
+    // Avoid adding new ones and keep in sync with the list there!
     router.get("/authorize_url", C(user::session::github_authorize));
     router.get("/authorize", C(user::session::github_access_token));
     router.delete("/logout", C(user::session::logout));