Fix edge subgraph

Project.toml

@@ -1,6 +1,6 @@
 name = "NamedGraphs"
 uuid = "678767b0-92e7-4007-89e4-4527a8725b19"
-version = "0.12.1"
+version = "0.12.2"
 authors = ["Matthew Fishman <mfishman@flatironinstitute.org>, Joseph Tindall <jtindall@flatironinstitute.org> and contributors"]
 
 [workspace]

src/abstractnamedgraph.jl

@@ -573,6 +573,11 @@ end
 function edge_subgraph_namedgraph(graph, edgelist)
     vs = unique(vcat(src.(edgelist), dst.(edgelist)))
     g = subgraph(graph, vs)
-    g = rem_edges!(g, setdiff(edges(g), edgelist))
+    edgeset = Set(edgelist)
+    for e in edges(g)
+        if !(e ∈ edgeset || reverse(e) ∈ edgeset)
+            rem_edge!(g, e)
+        end
+    end
     return g
 end

src/namedgraph.jl

@@ -225,3 +225,10 @@ end
 function GraphsExtensions.similar_graph(T::Type{<:GenericNamedGraph}, vertices)
     return T(vertices)
 end
+
+function edge_subgraph_namedgraph(graph::NamedDiGraph, edgelist)
+    vs = unique(vcat(src.(edgelist), dst.(edgelist)))
+    g = subgraph(graph, vs)
+    g = rem_edges!(g, setdiff(edges(g), edgelist))
+    return g
+end

test/test_namedgraph.jl

@@ -14,10 +14,11 @@ using Graphs: Edge, a_star, add_edge!, add_vertex!, adjacency_matrix,
 using GraphsFlows: GraphsFlows
 using NamedGraphs.GraphsExtensions: GraphsExtensions, boundary_edges, boundary_vertices,
     convert_vertextype, degrees, dijkstra_mst, dijkstra_parents, dijkstra_tree,
-    eccentricities, has_vertices, incident_edges, indegrees, inner_boundary_vertices,
-    mincut_partitions, outdegrees, outer_boundary_vertices, permute_vertices,
-    rename_vertices, subgraph, symrcm_perm, symrcm_permute, vertextype, ⊔
-using NamedGraphs.NamedGraphGenerators: named_binary_tree, named_grid, named_path_graph
+    eccentricities, edge_subgraph, has_vertices, incident_edges, indegrees,
+    inner_boundary_vertices, mincut_partitions, outdegrees, outer_boundary_vertices,
+    permute_vertices, rename_vertices, subgraph, symrcm_perm, symrcm_permute, vertextype, ⊔
+using NamedGraphs.NamedGraphGenerators:
+    named_binary_tree, named_grid, named_hexagonal_lattice_graph, named_path_graph
 using NamedGraphs: AbstractNamedEdge, NamedDiGraph, NamedEdge, NamedGraph, Vertices
 using SymRCM: SymRCM
 using Test: @test, @test_broken, @testset
@@ -118,6 +119,30 @@ end
         # Test Graphs.jl `getindex` syntax.
         @test g_sub == g[Vertices(["A", "B"])]
 
+        g_sub = edge_subgraph(g, NamedEdge.(["A" => "B"]))
+        @test has_vertex(g_sub, "A")
+        @test has_vertex(g_sub, "B")
+        @test !has_vertex(g_sub, "C")
+        @test !has_vertex(g_sub, "D")
+        @test has_edge(g_sub, "A" => "B")
+        # Test Graphs.jl `getindex` syntax.
+        @test g_sub == g[Vertices(["A", "B"])]
+
+        g = named_hexagonal_lattice_graph(3, 3)
+        es = NamedEdge.(
+            [
+                (1, 1) => (2, 1),
+                (2, 1) => (3, 1),
+                (3, 1) => (3, 2),
+                (2, 2) => (3, 2),
+                (1, 2) => (2, 2),
+                (1, 1) => (1, 2),
+            ]
+        )
+        @test all([e in edges(g) for e in es])
+        eg = edge_subgraph(g, es)
+        @test length(edges(eg)) == length(es)
+
         g = NamedGraph(["A", "B", "C", "D", "E"])
         add_edge!(g, "A" => "B")
         add_edge!(g, "B" => "C")