piecrust: add Session::set_meta

See also dusk-network/rusk#3341

piecrust/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Add `Session::set_meta` [#rusk_3341]
+
 ## [0.27.0] - 2024-12-18
 
 ### Added
@@ -485,6 +489,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 <!-- ISSUES -->
 
+[#rusk_3341]: https://github.com/dusk-network/rusk/issues/3341
 [#410]: https://github.com/dusk-network/piecrust/issues/410
 [#405]: https://github.com/dusk-network/piecrust/issues/405
 [#396]: https://github.com/dusk-network/piecrust/issues/396

piecrust/src/session.rs

@@ -748,6 +748,22 @@ impl Session {
         self.inner.data.get(name)
     }
 
+    /// Set the value of a metadata item.
+    ///
+    /// Returns the previous value of the metadata item.
+    pub fn set_meta<S, V>(
+        &mut self,
+        name: S,
+        value: V,
+    ) -> Result<Option<Vec<u8>>, Error>
+    where
+        S: Into<Cow<'static, str>>,
+        V: for<'a> Serialize<StandardBufSerializer<'a>>,
+    {
+        let data = Self::serialize_data(&value)?;
+        Ok(self.inner.data.set(name, data))
+    }
+
     pub fn serialize_data<V>(value: &V) -> Result<Vec<u8>, Error>
     where
         V: for<'a> Serialize<StandardBufSerializer<'a>>,
@@ -893,6 +909,13 @@ impl SessionData {
     fn get(&self, name: &str) -> Option<Vec<u8>> {
         self.data.get(name).cloned()
     }
+
+    fn set<S>(&mut self, name: S, data: Vec<u8>) -> Option<Vec<u8>>
+    where
+        S: Into<Cow<'static, str>>,
+    {
+        self.data.insert(name.into(), data)
+    }
 }
 
 impl From<SessionDataBuilder> for SessionData {