Fix Vector-of-Integers bug (#33)

* Flatten Vector{<:Integer} is empty

* Bump patch version

* Fix method specificity problem

* Apply suggestions from code review

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Project.toml

@@ -1,7 +1,7 @@
 name = "ParameterHandling"
 uuid = "2412ca09-6db7-441c-8e3a-88d5709968c5"
 authors = ["Invenia Technical Computing Corporation"]
-version = "0.3.3"
+version = "0.3.4"
 
 [deps]
 Bijectors = "76274a88-744f-5084-9051-94815aaf08c4"

src/flatten.jl

@@ -31,9 +31,20 @@ function flatten(::Type{T}, x::R) where {T<:Real, R<:Real}
     return v, unflatten_to_Real
 end
 
-flatten(::Type{T}, x::Vector{R}) where {T<:Real, R<:Real} = (Vector{T}(x), Vector{R})
+flatten(::Type{T}, x::Vector{R}) where {T<:Real,R<:Real} = (Vector{T}(x), Vector{R})
 
-function flatten(::Type{T}, x::AbstractVector) where T<:Real
+function _flatten_vector_integer(::Type{T}, x::AbstractVector{<:Integer}) where {T<:Real}
+    unflatten_to_Vector_Integer(x_vec) = x
+    return T[], unflatten_to_Vector_Integer
+end
+
+flatten(::Type{T}, x::Vector{<:Integer}) where {T<:Real} = _flatten_vector_integer(T, x)
+
+function flatten(::Type{T}, x::AbstractVector{<:Integer}) where {T<:Real}
+    return _flatten_vector_integer(T, x)
+end
+
+function flatten(::Type{T}, x::AbstractVector) where {T<:Real}
     x_vecs_and_backs = map(val -> flatten(T, val), x)
     x_vecs, backs = first.(x_vecs_and_backs), last.(x_vecs_and_backs)
     function Vector_from_vec(x_vec)

test/flatten.jl

@@ -13,6 +13,12 @@
         test_flatten_interface(randn(10))
         test_flatten_interface(randn(5, 4))
         test_flatten_interface([randn(5) for _ in 1:3])
+
+        # Prevent regression of https://github.com/invenia/ParameterHandling.jl/issues/31
+        @testset for v in [[1, 2, 3], sparse([1, 0, 3])]
+            test_flatten_interface(v)
+            @test length(first(flatten(v))) == 0
+        end
     end
 
     @testset "SparseMatrixCSC" begin