Add resize!()

Also fix too broad signature for append!() and push!(), and introduce a new
CatVector alias.

src/array.jl

@@ -607,13 +607,22 @@ using the ordering of levels. Return the modified `A`.
 """
 ordered!(A::CatArray, ordered) = (ordered!(A.pool, ordered); return A)
 
-function Base.push!(A::CatArray, item)
+function Base.resize!(A::CatVector, n::Integer)
+    n_orig = length(A)
+    resize!(A.refs, n)
+    if n > n_orig
+        A.refs[n_orig+1:end] = 0
+    end
+    A
+end
+
+function Base.push!(A::CatVector, item)
     resize!(A.refs, length(A.refs) + 1)
     A[end] = item
     return A
 end
 
-function Base.append!(A::CatArray, B::CatArray)
+function Base.append!(A::CatVector, B::CatArray)
     levels!(A, union(levels(A), levels(B)))
     len = length(A.refs)
     len2 = length(B.refs)

src/typedefs.jl

@@ -87,3 +87,4 @@ end
 ## Type Aliases
 
 @compat CatArray{T, N, R} = Union{CategoricalArray{T, N, R}, NullableCategoricalArray{T, N, R}}
+@compat CatVector{T, R} = Union{CategoricalVector{T, R}, NullableCategoricalVector{T, R}}

test/13_arraycommon.jl

@@ -189,6 +189,18 @@ for (CA, A) in ((CategoricalArray, Array), (NullableCategoricalArray, NullableAr
     @test_throws BoundsError copy!(x, 1, y, 4, 2)
     @test x == a
 
+    # Test resize!()
+    x = CA(["Old", "Young", "Middle", "Young"])
+    @test resize!(x, 3) === x
+    @test x == A(["Old", "Young", "Middle"])
+    @test resize!(x, 4) === x
+    if CA === NullableCategoricalArray
+        @test x == A(["Old", "Young", "Middle", Nullable()])
+    else
+        @test x[1:3] == A(["Old", "Young", "Middle"])
+        @test !isassigned(x, 4)
+    end
+
     for (sstart, dstart, n) in ((1, 1, 4), (1, 2, 3))
         # Conflicting orders: check that the destination wins and that result is not ordered
         x = CA(["Old", "Young", "Middle", "Young"])