From 9c5d0912ec3e8c2689e1ab23d4be4fdd0e03a9cc Mon Sep 17 00:00:00 2001
From: Jeb Rosen <jeb@jebrosen.com>
Date: Thu, 22 Aug 2019 14:18:44 -0700
Subject: [PATCH] Explain how to resolve the One-At-A-Time Cookies problem when
 using FlashMessage.

Fixes #1090.
---
 site/guide/4-requests.md | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/site/guide/4-requests.md b/site/guide/4-requests.md
index 3338292e..f26fd3d8 100644
--- a/site/guide/4-requests.md
+++ b/site/guide/4-requests.md
@@ -623,6 +623,25 @@ guards:
 fn good(custom: Custom, cookies: Cookies) { .. }
 ```
 
+When using request guards that modify cookies on-demand, such as
+`FlashMessage`, a similar problem occurs. The fix in this case is to `drop` the
+`Cookies` instance before accessing the `FlashMessage`.
+
+```rust
+#[get("/")]
+fn bad(cookies: Cookies, flash: FlashMessage) {
+    let msg = flash.msg();
+}
+```
+
+```rust
+#[get("/")]
+fn good(cookies: Cookies, flash: FlashMessage) {
+    std::mem::drop(cookies);
+    let msg = flash.msg();
+}
+```
+
 ## Format
 
 A route can specify the data format it is willing to accept or respond with by