From 04533a15fa1652e047f51d439aa2fe7be8ccc1de Mon Sep 17 00:00:00 2001
From: Akos Vandra-Meyer <axos88@users.noreply.github.com>
Date: Sun, 9 Feb 2025 23:04:21 +0100
Subject: [PATCH] Add `Extensions::get_or_insert[_with]()` methods (#3561)

* add get_or_insert and get_or_insert_with for Extensions

* add docs

* fix doctest

* docs: update changelog

* chore: simplify get_or_insert

---------

Co-authored-by: Rob Ede <robjtede@icloud.com>
---
 actix-http/CHANGES.md        |  1 +
 actix-http/src/extensions.rs | 40 ++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/actix-http/CHANGES.md b/actix-http/CHANGES.md
index 982add26a..23ebe43e1 100644
--- a/actix-http/CHANGES.md
+++ b/actix-http/CHANGES.md
@@ -5,6 +5,7 @@
 ### Added
 
 - Add `header::CLEAR_SITE_DATA` constant.
+- Add `Extensions::get_or_insert[_with]()` methods.
 
 ### Changed
 
diff --git a/actix-http/src/extensions.rs b/actix-http/src/extensions.rs
index 2ed3973bf..9c85caf37 100644
--- a/actix-http/src/extensions.rs
+++ b/actix-http/src/extensions.rs
@@ -104,6 +104,46 @@ impl Extensions {
             .and_then(|boxed| boxed.downcast_mut())
     }
 
+    /// Inserts the given `value` into the extensions if it is not present, then returns a reference
+    /// to the value in the extensions.
+    ///
+    /// ```
+    /// # use actix_http::Extensions;
+    /// let mut map = Extensions::new();
+    /// assert_eq!(map.get::<Vec<u32>>(), None);
+    ///
+    /// map.get_or_insert(Vec::<u32>::new()).push(1);
+    /// assert_eq!(map.get::<Vec<u32>>(), Some(&vec![1]));
+    ///
+    /// map.get_or_insert(Vec::<u32>::new()).push(2);
+    /// assert_eq!(map.get::<Vec<u32>>(), Some(&vec![1,2]));
+    /// ```
+    pub fn get_or_insert<T: 'static>(&mut self, value: T) -> &mut T {
+        self.get_or_insert_with(|| value)
+    }
+
+    /// Inserts a value computed from `f` into the extensions if the given `value` is not present,
+    /// then returns a reference to the value in the extensions.
+    ///
+    /// ```
+    /// # use actix_http::Extensions;
+    /// let mut map = Extensions::new();
+    /// assert_eq!(map.get::<Vec<u32>>(), None);
+    ///
+    /// map.get_or_insert_with(Vec::<u32>::new).push(1);
+    /// assert_eq!(map.get::<Vec<u32>>(), Some(&vec![1]));
+    ///
+    /// map.get_or_insert_with(Vec::<u32>::new).push(2);
+    /// assert_eq!(map.get::<Vec<u32>>(), Some(&vec![1,2]));
+    /// ```
+    pub fn get_or_insert_with<T: 'static, F: FnOnce() -> T>(&mut self, default: F) -> &mut T {
+        self.map
+            .entry(TypeId::of::<T>())
+            .or_insert_with(|| Box::new(default()))
+            .downcast_mut()
+            .expect("extensions map should now contain a T value")
+    }
+
     /// Remove an item from the map of a given type.
     ///
     /// If an item of this type was already stored, it will be returned.