Add accepted_field_type for Unions with Missing (#96)

PR #89 fixed compatibility with Arrow v2.6 except when the schema
field's declared type is e.g. `Union{Vector{T},Missing}` and what's
passed for validation is some `AbstractVector`. This adds a method to
`accepted_field_type` that recurses on the non-`Missing` type in a
`Union` with `Missing`. Note that this also necessitated adding an
explicit `accepted_field_type` method for `Any` to avoid infinite
recursion with the fallback definition, since `(Union{T,Missing} where
{T}) == Any`.

Project.toml

@@ -1,7 +1,7 @@
 name = "Legolas"
 uuid = "741b9549-f6ed-4911-9fbf-4a1c0c97f0cd"
 authors = ["Beacon Biosignals, Inc."]
-version = "0.5.11"
+version = "0.5.12"
 
 [deps]
 Arrow = "69666777-d1a9-59fb-9406-91d4454c9d45"

src/schemas.jl

@@ -240,22 +240,26 @@ record type.
 Legolas itself defines the following default overloads:
 
     accepted_field_type(::SchemaVersion, T::Type) = T
+    accepted_field_type(::SchemaVersion, ::Type{Any}) = Any
     accepted_field_type(::SchemaVersion, ::Type{UUID}) = Union{UUID,UInt128}
     accepted_field_type(::SchemaVersion, ::Type{Symbol}) = Union{Symbol,AbstractString}
     accepted_field_type(::SchemaVersion, ::Type{String}) = AbstractString
     accepted_field_type(sv::SchemaVersion, ::Type{<:Vector{T}}) where T = AbstractVector{<:(accepted_field_type(sv, T))}
     accepted_field_type(::SchemaVersion, ::Type{Vector}) = AbstractVector
+    accepted_field_type(sv::SchemaVersion, ::Type{Union{T,Missing}}) where {T} = Union{accepted_field_type(sv, T),Missing}
 
 Outside of these default overloads, this function should only be overloaded against specific
 `SchemaVersion`s that are authored within the same module as the overload definition; to do
 otherwise constitutes type piracy and should be avoided.
 """
 @inline accepted_field_type(::SchemaVersion, T::Type) = T
+accepted_field_type(::SchemaVersion, ::Type{Any}) = Any
 accepted_field_type(::SchemaVersion, ::Type{UUID}) = Union{UUID,UInt128}
 accepted_field_type(::SchemaVersion, ::Type{Symbol}) = Union{Symbol,AbstractString}
 accepted_field_type(::SchemaVersion, ::Type{String}) = AbstractString
 accepted_field_type(sv::SchemaVersion, ::Type{<:Vector{T}}) where T = AbstractVector{<:(accepted_field_type(sv, T))}
 accepted_field_type(::SchemaVersion, ::Type{Vector}) = AbstractVector
+accepted_field_type(sv::SchemaVersion, ::Type{Union{T,Missing}}) where {T} = Union{accepted_field_type(sv, T),Missing}
 
 """
     Legolas.find_violation(ts::Tables.Schema, sv::Legolas.SchemaVersion)

test/runtests.jl

@@ -276,6 +276,12 @@ end
     i::(<:Integer)
 end
 
+@schema "test.union-with-param" UnionWithParam
+
+@version UnionWithParamV1 begin
+    xs::Union{Vector{String},Missing}
+end
+
 @testset "`Legolas.@version` and associated utilities for declared `Legolas.SchemaVersion`s" begin
     @testset "Legolas.SchemaVersionDeclarationError" begin
         @test_throws SchemaVersionDeclarationError("malformed or missing declaration of required fields") eval(:(@version(NewV1, $(Expr(:block, LineNumberNode(1, :test))))))
@@ -401,6 +407,14 @@ end
         for T in (UUID, UInt128), S in (Symbol, String)
             @test Legolas.complies_with(Tables.Schema((:id, :sym), (T, S)), AcceptedV1SchemaVersion())
         end
+
+        t = Tables.Schema((:xs,), (SubArray{String,1,Arrow.List{String,Int32,Vector{UInt8}},
+                                            Tuple{UnitRange{Int64}},true},))
+        s = UnionWithParamV1SchemaVersion()
+        @test isnothing(Legolas.validate(t, s))
+        @test Legolas.complies_with(t, s)
+        @test isnothing(Legolas.find_violation(t, s))
+        @test isempty(Legolas.find_violations(t, s))
     end
 
     @testset "Legolas.declaration" begin