Support cloning an execution context

Cargo.toml

@@ -20,6 +20,7 @@ backtrace = "0.3"
 cfg-if = "1"
 cidr = { version = "0.2", features = ["serde"] }
 criterion = "0.5"
+dyn-clone = "1.0.20"
 fnv = "1.0.6"
 getrandom = { version = "0.3" }
 indoc = "2"

engine/Cargo.toml

@@ -23,6 +23,7 @@ harness = false
 backtrace.workspace = true
 cfg-if.workspace = true
 cidr.workspace = true
+dyn-clone.workspace = true
 fnv.workspace = true
 memmem.workspace = true
 rand.workspace = true

engine/src/execution_context.rs

@@ -224,6 +224,17 @@ impl<'e, U> ExecutionContext<'e, U> {
         ExecutionContextGuard::new(self, user_data)
     }
 
+    /// Clone the current [`ExecutionContext`] into a new one.
+    #[inline]
+    pub fn clone_with<T>(&self, user_data: T) -> ExecutionContext<'e, T> {
+        ExecutionContext {
+            scheme: self.scheme.clone(),
+            values: self.values.clone(),
+            list_matchers: self.list_matchers.clone(),
+            user_data,
+        }
+    }
+
     /// Clears the execution context, removing all values and lists
     /// while retaining the allocated memory.
     #[inline]

engine/src/list_matcher.rs

@@ -1,5 +1,6 @@
 use crate::LhsValue;
 use crate::Type;
+use dyn_clone::DynClone;
 use serde_json::Value;
 use std::any::Any;
 use std::fmt::Debug;
@@ -58,7 +59,7 @@ impl<T: PartialEq + Any> DynPartialEq for T {
 }
 
 /// Implement this Trait to match a given `LhsValue` against a list.
-pub trait ListMatcher: AsAny + Debug + DynPartialEq + Send + Sync + 'static {
+pub trait ListMatcher: AsAny + Debug + DynClone + DynPartialEq + Send + Sync + 'static {
     /// Returns true if `val` is in the given list.
     fn match_value(&self, list_name: &str, val: &LhsValue<'_>) -> bool;
 
@@ -69,6 +70,8 @@ pub trait ListMatcher: AsAny + Debug + DynPartialEq + Send + Sync + 'static {
     fn clear(&mut self);
 }
 
+dyn_clone::clone_trait_object!(ListMatcher);
+
 impl PartialEq for dyn ListMatcher {
     #[inline]
     fn eq(&self, other: &dyn ListMatcher) -> bool {