Fix mergesorted bug (#553)

Author: jkrumbiegel

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 - Added ability to return `ProcessedLayers` from transformations, thereby enabling multi-layer transformations, such as scatter plus errorbars [#549](https://github.com/MakieOrg/AlgebraOfGraphics.jl/pull/549).
+- Fixed bug where `mergesorted` applied on string vectors used `isless` instead of natural sort [#553](https://github.com/MakieOrg/AlgebraOfGraphics.jl/pull/553).
 
 ## v0.8.6 - 2024-09-02
 

src/scales.jl

@@ -493,7 +493,7 @@ function mergesorted(v1, v2)
     v = sizehint!(T[], length(v1) + length(v2))
     i1, i2 = 1, 1
     while i2 ≤ length(v2)
-        while i1 ≤ length(v1) && isless(v1[i1], v2[i2])
+        while i1 ≤ length(v1) && natural_lt(v1[i1], v2[i2])
             push_different!(v, v1[i1])
             i1 += 1
         end

test/utils.jl

@@ -11,6 +11,10 @@
     @test AlgebraOfGraphics.extend_extrema(e1, e2) == (-5, 11)
 
     @test AlgebraOfGraphics.midpoints(1:10) == 1.5:9.5
+
+    # issue 552
+    v = ["1", "9", "10"]
+    @test AlgebraOfGraphics.mergesorted(v, v) == v
 end
 
 @testset "arguments" begin