feat(gax): add mutable extension accessors to RequestOptions

Cargo.toml

@@ -511,7 +511,7 @@ tokio-stream      = { default-features = false, version = "0.1.16" }
 
 # Local packages used as dependencies.
 google-cloud-auth        = { default-features = false, version = "1.15.0", path = "src/auth" }
-google-cloud-gax         = { default-features = false, version = "1.13.0", path = "src/gax" }
+google-cloud-gax         = { default-features = false, version = "1.14.0", path = "src/gax" }
 gaxi                     = { default-features = false, version = "0.7.16", path = "src/gax-internal", package = "google-cloud-gax-internal" }
 wkt                      = { default-features = false, version = "1.7.0", path = "src/wkt", package = "google-cloud-wkt" }
 google-cloud-wkt         = { default-features = false, version = "1.7.0", path = "src/wkt", package = "google-cloud-wkt" }

librarian.yaml

@@ -889,7 +889,7 @@ libraries:
     version: 1.13.0
     copyright_year: "2025"
   - name: google-cloud-gax
-    version: 1.13.0
+    version: 1.14.0
     copyright_year: "2025"
     output: src/gax
   - name: google-cloud-gax-internal

src/gax/Cargo.toml

@@ -18,7 +18,7 @@ name = "google-cloud-gax"
 #     version of all downstream dependencies. For details see:
 #         https://github.com/googleapis/google-cloud-rust/issues/3237
 #         https://github.com/googleapis/google-cloud-rust/issues/3265
-version     = "1.13.0"
+version     = "1.14.0"
 description = "Google Cloud Client Libraries for Rust"
 # Inherit other attributes from the workspace.
 authors.workspace      = true

src/gax/src/options.rs

@@ -265,6 +265,16 @@ pub mod internal {
         where
             T: Send + Sync + 'static;
 
+        /// Gets a mutable reference to an extension value.
+        fn get_extension_mut<T>(&mut self) -> Option<&mut T>
+        where
+            T: Send + Sync + 'static;
+
+        /// Gets a mutable reference to an extension value, inserting the default if it does not exist.
+        fn get_extension_or_default_mut<T>(&mut self) -> &mut T
+        where
+            T: Default + Clone + Send + Sync + 'static;
+
         /// Sets an extension value.
         fn insert_extension<T>(self, value: T) -> Self
         where
@@ -280,6 +290,25 @@ pub mod internal {
             self.extensions.get::<T>()
         }
 
+        fn get_extension_mut<T>(&mut self) -> Option<&mut T>
+        where
+            T: Send + Sync + 'static,
+        {
+            self.extensions.get_mut::<T>()
+        }
+
+        fn get_extension_or_default_mut<T>(&mut self) -> &mut T
+        where
+            T: Default + Clone + Send + Sync + 'static,
+        {
+            if self.extensions.get::<T>().is_none() {
+                let _ = self.extensions.insert(T::default());
+            }
+            self.extensions
+                .get_mut::<T>()
+                .expect("value was just inserted if missing")
+        }
+
         fn insert_extension<T>(mut self, value: T) -> Self
         where
             T: Clone + Send + Sync + 'static,
@@ -466,6 +495,36 @@ mod tests {
         assert_eq!(opts.get_extension::<TestB>(), Some(&TestB(42)), "{opts:?}");
     }
 
+    #[test]
+    fn request_options_ext_mut() {
+        #[derive(Debug, Clone, Default, PartialEq)]
+        struct TestCounter(u32);
+
+        let mut opts = RequestOptions::default();
+
+        // 1. get_extension_mut returns None when not present.
+        assert!(opts.get_extension_mut::<TestCounter>().is_none());
+
+        // 2. get_extension_or_default_mut inserts default TestCounter(0) and returns mutable reference.
+        let counter = opts.get_extension_or_default_mut::<TestCounter>();
+        assert_eq!(counter, &mut TestCounter(0));
+        counter.0 += 10;
+
+        // 3. get_extension_mut returns Some(&mut TestCounter(10)) when present.
+        let counter = opts
+            .get_extension_mut::<TestCounter>()
+            .expect("counter extension should be present after insertion");
+        assert_eq!(counter, &mut TestCounter(10));
+        counter.0 += 10;
+
+        // 4. Second call to get_extension_or_default_mut returns existing reference without resetting.
+        let counter2 = opts.get_extension_or_default_mut::<TestCounter>();
+        assert_eq!(counter2, &mut TestCounter(20));
+        counter2.0 += 5;
+
+        assert_eq!(opts.get_extension::<TestCounter>(), Some(&TestCounter(25)));
+    }
+
     #[test]
     fn request_options_builder() -> anyhow::Result<()> {
         const USER_AGENT: &str = "test-only";