enforce that levels are unique for ContrastsMatrix (#231)

* enforce that levels are unique for ContrastsMatrix

* add test + bump patch version

Author: kleinschmidt

Project.toml

@@ -1,6 +1,6 @@
 name = "StatsModels"
 uuid = "3eaba693-59b7-5ba5-a881-562e759f1c8d"
-version = "0.6.23"
+version = "0.6.24"
 
 [deps]
 DataAPI = "9a962f9c-6df0-11e9-0e5d-c546b8b5ee8a"

src/contrasts.jl

@@ -111,6 +111,7 @@ struct ContrastsMatrix{C <: AbstractContrasts, T, U}
                              termnames::Vector{U},
                              levels::Vector{T},
                              contrasts::C) where {U,T,C <: AbstractContrasts}
+        allunique(levels) || throw(ArgumentError("levels must be all unique, got $(levels)"))
         invindex = Dict{T,Int}(x=>i for (i,x) in enumerate(levels))
         new{C,T,U}(matrix, termnames, levels, contrasts, invindex)
     end

test/contrasts.jl

@@ -332,4 +332,9 @@
         @test_throws MethodError ContrastsCoding(rand(4,3), base=base)
 
     end
+
+    @testset "Non-unique levels" begin
+        @test_throws ArgumentError ContrastsMatrix(DummyCoding(), ["a", "a", "b"])
+    end
+    
 end