Add serde support for graphmap (#496)

* Add from_graph function for graphmap

* Add serde support for graphmap

README.md

@@ -11,7 +11,7 @@ Crate feature flags:
 -   `graphmap` (default) enable `GraphMap`.
 -   `stable_graph` (default) enable `StableGraph`.
 -   `matrix_graph` (default) enable `MatrixGraph`.
--   `serde-1` (optional) enable serialization for `Graph, StableGraph`
+-   `serde-1` (optional) enable serialization for `Graph, StableGraph, GraphMap`
     using serde 1.0. Requires Rust version as required by serde.
 
 ## Recent Changes

serialization-tests/Cargo.toml

@@ -10,15 +10,17 @@ authors = [
 
 description = ""
 documentation = ""
-repository = "https://github.com/bluss/petgraph"
+repository = "https://github.com/petgraph/petgraph"
 
 
 [dependencies]
 petgraph = { path = "..", features = ["serde-1", "quickcheck"] }
 itertools = { version = "0.10.1" }
 
 [dev-dependencies]
+serde = "1.0"
 serde_json = "1.0"
+serde_derive = "1.0"
 quickcheck = { version = "0.8", default-features = false }
 bincode = "1.3.3"
 defmac = "0.2.1"

serialization-tests/tests/serialization.rs

@@ -3,6 +3,7 @@ extern crate petgraph;
 extern crate quickcheck;
 extern crate bincode;
 extern crate itertools;
+extern crate serde_derive;
 extern crate serde_json;
 #[macro_use]
 extern crate defmac;
@@ -486,4 +487,80 @@ quickcheck! {
         let g2: StableGraph<i32, i32> = recode!(&g1);
         assert_stable_graph_eq(&g1, &g2);
     }
+
+    fn json_graphmap_to_graphmap(g1: DiGraphMap<i32, i32>) -> () {
+        let g2: DiGraphMap<i32, i32> = rejson!(&g1);
+        assert!(petgraph::algo::is_isomorphic(&g1, &g2));
+    }
+
+    fn bincode_graphmap_to_graphmap(g1: DiGraphMap<i8, ()>) -> () {
+        let g2: DiGraphMap<i8, ()> = recode!(&g1);
+        assert!(petgraph::algo::is_isomorphic(&g1, &g2));
+    }
+
+    fn bincode_graphmap_to_graph(g1: DiGraphMap<i8, i8>) -> () {
+        let g2: DiGraph<i8, i8> = recode!(&g1);
+        assert!(petgraph::algo::is_isomorphic(&g1, &g2));
+    }
+
+    // graph to graphmap is not always possible because of parallel edges
+}
+
+#[test]
+fn json_graphmap_integer() {
+    let mut gr: GraphMap<i32, u32, Directed> = GraphMap::from_edges(&[
+        (6, 0, 0),
+        (0, 3, 1),
+        (3, 6, 2),
+        (8, 6, 3),
+        (8, 2, 4),
+        (2, 5, 5),
+        (5, 8, 6),
+        (7, 5, 7),
+        (1, 7, 8),
+        (7, 4, 9),
+        (4, 1, 10),
+    ]);
+    // unconnected node
+    gr.add_node(42);
+
+    let gr_deser: GraphMap<i32, u32, Directed> = rejson!(&gr);
+    assert!(petgraph::algo::is_isomorphic(&gr, &gr_deser));
+    assert_eq!(gr_deser[(4, 1)], 10);
+}
+
+#[test]
+fn json_graphmap_struct() {
+    use serde_derive::{Deserialize, Serialize};
+
+    #[derive(Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
+    struct TestingNode {
+        pub a: u32,
+        pub b: i32,
+    }
+    let mut gr: GraphMap<TestingNode, (u8, f32), Undirected> = GraphMap::from_edges(&[
+        (
+            TestingNode { a: 42, b: -1 },
+            TestingNode { a: 12, b: -2 },
+            (1, 2.),
+        ),
+        (
+            TestingNode { a: 12, b: -2 },
+            TestingNode { a: 13, b: -3 },
+            (99, 99.),
+        ),
+        (
+            TestingNode { a: 13, b: -3 },
+            TestingNode { a: 42, b: -1 },
+            (99, 98.),
+        ),
+    ]);
+    gr.add_node(TestingNode { a: 0, b: 0 });
+
+    let gr_deser: GraphMap<TestingNode, (u8, f32), Undirected> = rejson!(&gr);
+    assert!(petgraph::algo::is_isomorphic(&gr, &gr_deser));
+    assert_eq!(
+        gr_deser[(TestingNode { a: 42, b: -1 }, TestingNode { a: 12, b: -2 })],
+        (1, 2.)
+    );
 }

src/graphmap.rs

@@ -116,6 +116,51 @@ impl PartialEq<Direction> for CompactDirection {
     }
 }
 
+#[cfg(feature = "serde-1")]
+impl<N, E, Ty> serde::Serialize for GraphMap<N, E, Ty>
+where
+    Ty: EdgeType,
+    N: NodeTrait + serde::Serialize,
+    E: serde::Serialize,
+    GraphMap<N, E, Ty>: Clone,
+{
+    /// Serializes the given `GraphMap` into the same format as the standard
+    /// `Graph`. Needs feature `serde-1`.
+    ///
+    /// Note: the graph has to be `Clone` for this to work.
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        let cloned_graph: GraphMap<N, E, Ty> = GraphMap::clone(self);
+        let equivalent_graph: Graph<N, E, Ty, u32> = cloned_graph.into_graph();
+        equivalent_graph.serialize(serializer)
+    }
+}
+
+#[cfg(feature = "serde-1")]
+impl<'de, N, E, Ty> serde::Deserialize<'de> for GraphMap<N, E, Ty>
+where
+    Ty: EdgeType,
+    N: NodeTrait + serde::Deserialize<'de>,
+    E: Clone + serde::Deserialize<'de>,
+{
+    /// Deserializes into a new `GraphMap` from the same format as the standard
+    /// `Graph`. Needs feature `serde-1`.
+    ///
+    /// **Warning**: When deseralizing a graph that was not originally a `GraphMap`,
+    /// the restrictions from [`from_graph`](#method.from_graph) apply.
+    ///
+    /// Note: The edge weights have to be `Clone` for this to work.
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let equivalent_graph: Graph<N, E, Ty, u32> = Graph::deserialize(deserializer)?;
+        Ok(GraphMap::from_graph(equivalent_graph))
+    }
+}
+
 impl<N, E, Ty> GraphMap<N, E, Ty>
 where
     N: NodeTrait,
@@ -477,6 +522,37 @@ where
         }
         gr
     }
+
+    /// Creates a `GraphMap` that corresponds to the given `Graph`.
+    ///
+    /// **Warning**: Nodes with the same weight are merged and only the last parallel edge
+    /// is kept. Node and edge indices of the `Graph` are lost. Only use this function
+    /// if the node weights are distinct and there are no parallel edges.
+    ///
+    /// Computes in **O(|V| + |E|)** time (average).
+    pub fn from_graph<Ix>(graph: Graph<N, E, Ty, Ix>) -> Self
+    where
+        Ix: crate::graph::IndexType,
+        E: Clone,
+    {
+        let mut new_graph: GraphMap<N, E, Ty> =
+            GraphMap::with_capacity(graph.node_count(), graph.edge_count());
+
+        for node in graph.raw_nodes() {
+            new_graph.add_node(node.weight);
+        }
+
+        for edge in graph.edge_indices() {
+            let (a, b) = graph.edge_endpoints(edge).unwrap();
+            new_graph.add_edge(
+                *graph.node_weight(a).unwrap(),
+                *graph.node_weight(b).unwrap(),
+                graph.edge_weight(edge).unwrap().clone(),
+            );
+        }
+
+        new_graph
+    }
 }
 
 /// Create a new `GraphMap` from an iterable of edges.

src/lib.rs

@@ -93,7 +93,7 @@
 //! # Crate features
 //!
 //! * **serde-1** -
-//!   Defaults off. Enables serialization for ``Graph, StableGraph`` using
+//!   Defaults off. Enables serialization for ``Graph, StableGraph, GraphMap`` using
 //!   [`serde 1.0`](https://crates.io/crates/serde). May require a more recent version
 //!   of Rust than petgraph alone.
 //! * **graphmap** -

tests/graphmap.rs

@@ -325,6 +325,26 @@ fn test_into_graph() {
     }
 }
 
+#[test]
+fn test_from_graph() {
+    let mut gr: Graph<u32, u32, Directed> = Graph::new();
+    let node_a = gr.add_node(12);
+    let node_b = gr.add_node(13);
+    let node_c = gr.add_node(14);
+    gr.add_edge(node_a, node_b, 1000);
+    gr.add_edge(node_b, node_c, 999);
+    gr.add_edge(node_c, node_a, 1111);
+    gr.add_node(42);
+    let gr = gr;
+
+    let graph: GraphMap<u32, u32, Directed> = GraphMap::from_graph(gr.clone());
+    println!("{}", Dot::new(&gr));
+    println!("{}", Dot::new(&graph));
+
+    assert!(petgraph::algo::is_isomorphic(&gr, &graph));
+    assert_eq!(graph[(12, 13)], 1000);
+}
+
 #[test]
 fn test_all_edges_mut() {
     // graph with edge weights equal to in+out