Add fill! method for CategoricalArray views to fix .=

src/subarray.jl

@@ -27,3 +27,12 @@ else
 end
 
 pool(A::SubArray{<:Any, <:Any, <:CategoricalArray}) = A.parent.pool
+
+function Base.fill!(A::SubArray{<:Any, <:Any, <:CategoricalArray}, v::Any)
+    r = get!(A.parent.pool, convert(leveltype(A.parent), v))
+    fill!(refs(A), r)
+    A
+end
+
+Base.fill!(A::SubArray{<:Any, <:Any, <:CategoricalArray{>:Missing}}, ::Missing) =
+    (fill!(refs(A), 0); A)

test/14_view.jl

@@ -3,6 +3,8 @@ using Compat
 using Compat.Test
 using CategoricalArrays
 
+const ≅ = isequal
+
 @testset "view($(CategoricalArray{Union{T, eltype(a)}}), $inds), ordered=$order construction" for
     T in (Union{}, Missing), order in (true, false),
     a in (1:10, 10:-1:1, ["a", "c", "b", "b", "a"]),
@@ -30,4 +32,17 @@ end
     @test view(ca1, 1:2) != view(ca5, 1:2, 1:1)
 end
 
+@testset "fill! on view" for
+    a in (categorical(["c", "a", "b"]), categorical(["c", "a", missing]))
+    v = view(a, 1:2)
+    @test fill!(v, a[1]) == ["c", "c"]
+    @test fill!(v, "a") == ["a", "a"]
+    @test fill!(v, "d") == ["d", "d"]
+    if eltype(a) >: Missing
+        @test fill!(v, missing) ≅ [missing, missing]
+    else
+        @test_throws MethodError fill!(v, missing)
+    end
+end
+
 end