Use levels from DataAPI (#216)

Author: nalimilan

Project.toml

@@ -14,7 +14,8 @@ Unicode = "4ec0a83e-493e-50e2-b9ac-8f72acf5a8f5"
 
 [compat]
 julia = "1"
-Missings = ">= 0.4.2"
+DataAPI = "1.1"
+Missings = ">= 0.4.3"
 
 [extras]
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"

src/array.jl

@@ -561,7 +561,7 @@ leveltype(::Type{T}) where {T <: CategoricalArray} = leveltype(catvaluetype(T))
 Return the levels of categorical array `A`. This may include levels which do not actually appear
 in the data (see [`droplevels!`](@ref)).
 """
-Missings.levels(A::CategoricalArray) = levels(A.pool)
+DataAPI.levels(A::CategoricalArray) = levels(A.pool)
 
 """
     levels!(A::CategoricalArray, newlevels::Vector; allow_missing::Bool=false)

src/pool.jl

@@ -280,7 +280,7 @@ function levels!(pool::CategoricalPool{S, R}, newlevels::Vector) where {S, R}
 end
 
 index(pool::CategoricalPool) = pool.index
-Missings.levels(pool::CategoricalPool) = pool.levels
+DataAPI.levels(pool::CategoricalPool) = pool.levels
 order(pool::CategoricalPool) = pool.order
 
 isordered(pool::CategoricalPool) = pool.ordered

src/subarray.jl

@@ -1,6 +1,6 @@
 # delegate methods for SubArrays to support view
 
-Missings.levels(sa::SubArray{T,N,P}) where {T,N,P<:CategoricalArray} = levels(parent(sa))
+DataAPI.levels(sa::SubArray{T,N,P}) where {T,N,P<:CategoricalArray} = levels(parent(sa))
 isordered(sa::SubArray{T,N,P}) where {T,N,P<:CategoricalArray} = isordered(parent(sa))
 # This method cannot support allow_missing=true since that would modify the parent
 levels!(sa::SubArray{T,N,P}, newlevels::Vector) where {T,N,P<:CategoricalArray} =