Add Clone to graph models, and tests

src/models/append_graph.rs

@@ -43,6 +43,7 @@ pub type AppendGraphEdgeMap<T> = ElementMap<Edge, T>;
 /// An [`Incidence`] for [`AppendGraph`].
 pub type AppendGraphIncidence = Incidence<Vertex, Edge>;
 
+#[derive(Clone)]
 struct VertexIncidenceHeader {
     incidence_count: usize,
     first_incidence: Option<Edge>,
@@ -101,11 +102,18 @@ impl IncidenceCursor<AppendGraph> for AppendGraphIncidenceCursor {
 /// Both [`add_vertex`] and [`add_edge`] run in amortised *O(1)* time. [`degree`] runs in *O(1)*
 /// time since vertex degrees are stored. Space complexity is *O(|V| + |E|)*.
 ///
+/// # Cloning
+///
+/// [`Vertex`] and [`Edge`] handles obtained from a clone are valid, and refer to the same vertex or
+/// edge in the original, and vice versa. However, once cloned, the two instances no longer affect
+/// each other.
+///
 /// [`add_vertex`]: Self::add_vertex
 /// [`add_edge`]: Self::add_edge
 /// [`degree`]: Self::degree
 /// [`FrozenGraph`]: crate::models::FrozenGraph
 /// [`Graph`]: crate::models::Graph
+#[derive(Clone)]
 pub struct AppendGraph {
     vertices: Vec<VertexIncidenceHeader>,
     incidences: Vec<IncidenceEntry>,
@@ -257,6 +265,8 @@ mod trait_tests {
 
     crate::graph_topology_tests!(AppendGraph);
     crate::graph_topology_addition_tests!(AppendGraph);
+    crate::graph_topology_clone_tests!(AppendGraph);
+    crate::graph_topology_addition_clone_tests!(AppendGraph);
 }
 
 #[cfg(test)]

src/models/frozen_graph.rs

@@ -87,9 +87,16 @@ impl IncidenceCursor<FrozenGraph> for FrozenGraphIncidenceCursor {
 ///
 /// [`degree`] runs in *O(1)* time. Space complexity is *O(|V| + |E|)*.
 ///
+/// # Cloning
+///
+/// [`Vertex`] and [`Edge`] handles obtained from a clone are valid, and refer to the same vertex or
+/// edge in the original, and vice versa. However, once cloned, the two instances no longer affect
+/// each other.
+///
 /// [`degree`]: Self::degree
 /// [`AppendGraph`]: crate::models::AppendGraph
 /// [`Graph`]: crate::models::Graph
+#[derive(Clone)]
 pub struct FrozenGraph {
     vertices: Vec<usize>,
     incidences: Vec<IncidenceEntry>,
@@ -255,6 +262,7 @@ mod trait_tests {
     use super::FrozenGraph;
 
     crate::graph_topology_tests!(FrozenGraph);
+    crate::graph_topology_clone_tests!(FrozenGraph);
 }
 
 #[cfg(test)]

src/models/graph.rs

@@ -49,6 +49,7 @@ impl IncidenceSlot {
 /// Referenced by [`Vertex`] as a type parameter of the underlying arena. Not intended for direct
 /// external use.
 #[doc(hidden)]
+#[derive(Clone)]
 pub struct VertexIncidenceHeader {
     incidence_count: usize,
     first_incidence: Option<IncidenceSlot>,
@@ -129,12 +130,19 @@ impl IncidenceCursor<Graph> for GraphIncidenceCursor {
 /// planned, performing deletions first allows freed slots to be reused by subsequent additions,
 /// potentially avoiding reallocation.
 ///
+/// # Cloning
+///
+/// [`Vertex`] and [`Edge`] handles obtained from a clone are valid, and refer to the same vertex or
+/// edge in the original, and vice versa. However, once cloned, the two instances no longer affect
+/// each other.
+///
 /// [`add_vertex`]: Self::add_vertex
 /// [`add_edge`]: Self::add_edge
 /// [`degree`]: Self::degree
 /// [`delete_vertex`]: Self::delete_vertex
 /// [`delete_edge`]: Self::delete_edge
 /// [`AppendGraph`]: crate::models::AppendGraph
+#[derive(Clone)]
 pub struct Graph {
     // TODO: Arena index and generation types could be externalized to Graph.
     vertices: Arena<VertexIncidenceHeader, usize, usize>,
@@ -398,6 +406,8 @@ mod trait_tests {
     crate::graph_topology_addition_tests!(Graph);
     crate::graph_topology_deletion_tests!(Graph);
     crate::graph_topology_addition_deletion_tests!(Graph);
+    crate::graph_topology_clone_tests!(Graph);
+    crate::graph_topology_addition_clone_tests!(Graph);
 }
 
 #[cfg(test)]