Use traits for (un)directed types

Project.toml

@@ -5,6 +5,7 @@ version = "0.4.0"
 [deps]
 Graphs = "86223c79-3864-5bf0-83f7-82e725a168b6"
 JLD2 = "033835bb-8acc-5ee8-8aae-3f567f8a3819"
+SimpleTraits = "699a6c99-e7fa-54fc-8d76-47d257e15c1d"
 
 [compat]
 Graphs = "1.4.1"

src/MetaGraphsNext.jl

@@ -2,6 +2,7 @@ module MetaGraphsNext
 
 using JLD2
 using Graphs
+using SimpleTraits
 
 export MetaGraph, MetaDiGraph, MetaUndirectedGraph
 export label_for, code_for, set_data

src/graphs.jl

@@ -41,6 +41,14 @@ function Base.issubset(meta_graph::MetaGraph, h::MetaGraph)
     issubset(meta_graph.graph, h.graph)
 end
 
+function Graphs.is_directed(meta_graph::MetaGraph)
+    Graphs.is_directed(meta_graph.graph)
+end
+
+function Graphs.is_directed(::Type{<:MetaGraph{Code, Label, Graph}}) where {Code,Label,Graph<:AbstractGraph}
+    Graphs.is_directed(Graph)
+end
+
 ## Link between graph codes and metagraph labels
 
 """
@@ -205,7 +213,7 @@ function Graphs.induced_subgraph(
     new_graph, code_map
 end
 
-function Graphs.reverse(meta_graph::MetaDiGraph)
+@traitfn function Graphs.reverse(meta_graph::MetaGraph::IsDirected)
     edge_data = meta_graph.edge_data
     reverse_edge_data = empty(edge_data)
     for (label_1, label_2) in keys(edge_data)

src/metadigraph.jl

@@ -1,26 +1,5 @@
-"""
-    MetaDiGraph
+@traitfn Graphs.SimpleDiGraph(meta_graph::MetaGraph::(IsDirected)) = meta_graph.graph
 
-A `MetaGraph` whose underlying graph is of type `Graphs.SimpleDiGraph`.
-"""
-const MetaDiGraph = MetaGraph{<:Any, <:Any, <:SimpleDiGraph}
-
-function Graphs.SimpleDiGraph(meta_graph::MetaDiGraph)
-    meta_graph.graph
-end
-
-function Graphs.is_directed(::Type{<:MetaDiGraph})
-    true
-end
-function Graphs.is_directed(::MetaDiGraph)
-    true
-end
-
-function arrange(
-    ::MetaDiGraph,
-    label_1,
-    label_2,
-    _...,
-)
+@traitfn function arrange(::AG::IsDirected, label_1, label_2, _drop...) where {T, AG <: AbstractGraph{T}}
     label_1, label_2
 end

src/metaundigraph.jl

@@ -1,33 +1,13 @@
-"""
-    MetaUndirectedGraph
+@traitfn Graphs.SimpleGraph(meta_graph::MetaGraph::(!IsDirected)) = meta_graph.graph
 
-A `MetaGraph` whose underlying graph is of type `Graphs.SimpleGraph`.
-"""
-const MetaUndirectedGraph = MetaGraph{<:Any, <:Any, <:SimpleGraph}
-
-Graphs.SimpleGraph(meta_graph::MetaUndirectedGraph) = meta_graph.graph
-
-Graphs.is_directed(::Type{<:MetaUndirectedGraph}) = false
-Graphs.is_directed(::MetaUndirectedGraph) = false
-
-function arrange(
-    ::MetaUndirectedGraph,
-    label_1,
-    label_2,
-    code_1,
-    code_2,
-)
+@traitfn function arrange(::AG::(!IsDirected), label_1, label_2, code_1, code_2) where {T, AG <: AbstractGraph{T}}
     if code_1 < code_2
         (label_1, label_2)
     else
         (label_2, label_1)
     end
 end
 
-function arrange(
-    meta_graph::MetaUndirectedGraph,
-    label_1,
-    label_2,
-)
+@traitfn function arrange(meta_graph::AG::(!IsDirected), label_1, label_2) where {T, AG <: AbstractGraph{T}}
     arrange(meta_graph, label_1, label_2, code_for(meta_graph, label_1), code_for(meta_graph, label_2))
 end

test/runtests.jl

@@ -2,11 +2,15 @@ using Documenter
 using MetaGraphsNext
 using Test
 using Graphs
+using SimpleTraits
 
 @testset "MetaGraphsNext" begin
     doctest(MetaGraphsNext)
 
     colors = MetaGraph( Graph(), VertexData = String, EdgeData = Symbol, graph_data = "graph_of_colors")
+    @test istrait(IsDirected{typeof(colors)}) == is_directed(colors) == false
+    @test SimpleGraph(colors) isa SimpleGraph
+    @test_throws MethodError SimpleDiGraph(colors)
 
     labels = [:red, :yellow, :blue]
     values = ["warm", "warm", "cool"]
@@ -23,4 +27,19 @@ using Graphs
     for label in labels
         @test label_for(colors, code_for(colors, label)) == label
     end
+    @test MetaGraphsNext.arrange(colors, :yellow, :blue) == (:blue, :yellow)
+
+
+    # directed MetaGraph
+    dcolors = MetaGraph( SimpleDiGraph(), VertexData = String, EdgeData = Symbol, graph_data = "graph_of_colors")
+    @test istrait(IsDirected{typeof(dcolors)}) == is_directed(dcolors) == true
+    @test SimpleDiGraph(dcolors) isa SimpleDiGraph
+    @test_throws MethodError SimpleGraph(dcolors)
+    labels = [:red, :yellow, :blue]
+    values = ["warm", "warm", "cool"]
+    for (label, value) in zip(labels, values)
+        dcolors[label] = value
+    end
+    dcolors[:red, :yellow] = :redyellow
+    @test MetaGraphsNext.arrange(dcolors, :yellow, :blue) == (:yellow, :blue)
 end