fix: avoid cloning if there is one reference to the content

Signed-off-by: Amin Yahyaabadi <[email protected]>

src/engine/dag.rs

@@ -354,17 +354,9 @@ impl Dag {
 
     /// Get the final execution result.
     ///
-    /// Note: This method will clone the value. To avoid cloning, use [`Dag::into_result`].
+    /// Note: This method might clone the value if there are references to the value. To avoid cloning, use [`Dag::into_result`].
     pub fn get_result<T: Send + Sync + Clone + 'static>(&self) -> Option<T> {
-        if self.exe_sequence.is_empty() {
-            None
-        } else {
-            let last_id = self.exe_sequence.last().unwrap();
-            match self.execute_states[last_id].get_output() {
-                Some(ref content) => content.get().cloned(),
-                None => None,
-            }
-        }
+        self.into_result::<T>().map(unwrap_or_clone)
     }
 
     /// Get the output of all tasks.
@@ -382,12 +374,12 @@ impl Dag {
 
     /// Get the output of all tasks.
     ///
-    /// Note: This method will clone the value. To avoid cloning, use [`Dag::into_results`].
+    /// Note: This method might clone the value if there are references to the value. To avoid cloning, use [`Dag::into_results`].
     pub fn get_results<T: Send + Sync + Clone + 'static>(&self) -> HashMap<usize, Option<T>> {
         let mut hm = HashMap::new();
         for (id, state) in &self.execute_states {
             let output = match state.get_output() {
-                Some(ref content) => content.get().cloned(),
+                Some(content) => content.into_inner().map(unwrap_or_clone),
                 None => None,
             };
             hm.insert(*id, output);
@@ -400,3 +392,9 @@ impl Dag {
         self.env = Arc::new(env);
     }
 }
+
+/// Unwrap an Arc<T> to T if possible, otherwise clone the value.
+// This can be removed when Arc::unwrap_or_clone is stabilized.
+fn unwrap_or_clone<T: Send + Sync + Clone + 'static>(arc: Arc<T>) -> T {
+    Arc::try_unwrap(arc).unwrap_or_else(|arc| (*arc).clone())
+}