Update dependencies, Julia compat, and add weak dependencies

Project.toml

@@ -1,27 +1,34 @@
 name = "NetworkLayout"
 uuid = "46757867-2c16-5918-afeb-47bfcb05e46a"
-version = "0.4.6"
+version = "0.4.7"
 
 [deps]
 GeometryBasics = "5c1252a2-5f33-56bf-86c9-59e7332b4326"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 Requires = "ae029012-a4dd-5104-9daa-d747884805df"
-SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
 
 [compat]
 GeometryBasics = "0.4"
+Graphs = "1"
 Requires = "1"
 StaticArrays = "1"
-julia = "1"
+julia = "1.6"
+
+[extensions]
+NetworkLayoutGraphsExt = "Graphs"
 
 [extras]
 DelimitedFiles = "8bb1440f-4735-579b-a4ab-409b98df4dab"
 GeometryTypes = "4d00f742-c7ba-57c2-abde-4428a4b178cb"
 Graphs = "86223c79-3864-5bf0-83f7-82e725a168b6"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
+SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Graphs", "Test", "DelimitedFiles", "GeometryTypes"]
+test = ["Graphs", "Test", "DelimitedFiles", "GeometryTypes", "SparseArrays"]
+
+[weakdeps]
+Graphs = "86223c79-3864-5bf0-83f7-82e725a168b6"

ext/NetworkLayoutGraphsExt.jl

@@ -0,0 +1,18 @@
+module NetworkLayoutGraphsExt
+
+if isdefined(Base, :get_extension)
+    import NetworkLayout
+    import Graphs
+else
+    import ..NetworkLayout
+    import ..Graphs
+end
+
+function NetworkLayout.layout(l::NetworkLayout.AbstractLayout, g::Graphs.AbstractGraph)
+    NetworkLayout.layout(l, Graphs.adjacency_matrix(g))
+end
+function NetworkLayout.LayoutIterator(l::NetworkLayout.IterativeLayout, g::Graphs.AbstractGraph)
+    NetworkLayout.LayoutIterator(l, Graphs.adjacency_matrix(g))
+end
+
+end # module

src/NetworkLayout.jl

@@ -1,7 +1,6 @@
 module NetworkLayout
 
 using GeometryBasics
-using Requires
 using LinearAlgebra: norm
 using Random
 using StaticArrays
@@ -86,21 +85,13 @@ function layout(alg::IterativeLayout, adj_matrix::AbstractMatrix)
     return pos
 end
 
-function __init__()
-    @require LightGraphs = "093fc24a-ae57-5d10-9952-331d41423f4d" begin
-        function layout(l::AbstractLayout, g::LightGraphs.AbstractGraph)
-            layout(l, LightGraphs.adjacency_matrix(g))
-        end
-        function LayoutIterator(l::IterativeLayout, g::LightGraphs.AbstractGraph)
-            LayoutIterator(l, LightGraphs.adjacency_matrix(g))
-        end
-    end
-    @require Graphs = "86223c79-3864-5bf0-83f7-82e725a168b6" begin
-        function layout(l::AbstractLayout, g::Graphs.AbstractGraph)
-            layout(l, Graphs.adjacency_matrix(g))
-        end
-        function LayoutIterator(l::IterativeLayout, g::Graphs.AbstractGraph)
-            LayoutIterator(l, Graphs.adjacency_matrix(g))
+if !isdefined(Base, :get_extension)
+    using Requires
+end
+@static if !isdefined(Base, :get_extension)
+    function __init__()
+        @require Graphs = "86223c79-3864-5bf0-83f7-82e725a168b6" begin
+            include("../ext/NetworkLayoutGraphsExt.jl")
         end
     end
 end

src/stress.jl

@@ -1,5 +1,4 @@
 using LinearAlgebra: checksquare, norm, pinv, mul!
-using SparseArrays: SparseMatrixCSC
 
 export Stress, stress