Fix union{} (#534)

* Union{} is weird * add test * version and changelog
JuliaIO · Jan 16, 2024 · 15eaa50 · 15eaa50 · JonasIsensee · Jan 16, 2024
1 parent 3e14317
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,3 +1,6 @@
+## 0.4.44
+ - fix dispatch around `Union{}` as type parameter
+
 ## 0.4.43
  - do not try to `rconvert` `#undef` array elements (#529)
 

diff --git a/Project.toml b/Project.toml
@@ -1,6 +1,6 @@
 name = "JLD2"
 uuid = "033835bb-8acc-5ee8-8aae-3f567f8a3819"
-version = "0.4.43"
+version = "0.4.44"
 
 [deps]
 FileIO = "5789e2e9-d7fb-5bc7-8068-2c6fae9b9549"

diff --git a/src/data/reconstructing_datatypes.jl b/src/data/reconstructing_datatypes.jl
@@ -330,6 +330,7 @@ end
 
 isunknowntype(x::Type{<:UnknownType}) = true
 isunknowntype(x) = false
+isunknowntype(::Type{Union{}}) = false
 
 function _resolve_type(rr::ReadRepresentation{T,DataTypeODR()},
                        f::JLDFile,
@@ -475,6 +476,7 @@ end
 isreconstructed(x) = isreconstructed(typeof(x))
 isreconstructed(x::Type{<:AbstractReconstructedType}) = true
 isreconstructed(x::Type) = false
+isreconstructed(x::Type{Union{}}) = false
 
 function reconstruct_bitstype(name::Union{Symbol,String}, size::Integer, empty::Bool)
     if empty

diff --git a/test/loadsave.jl b/test/loadsave.jl
@@ -731,4 +731,12 @@ end
         @test load(fn, "b/d/f", "a") == (Dict("g" => 4), 1)
         @test load(fn, "b/d") == Dict("e" => 3, "f" => Dict("g"=> 4))
     end
+end
+
+@testset "Union{} in type signature Issue #532" begin
+    cd(mktempdir()) do 
+        op = (1, pairs((;)))
+        jldsave("testopempty.jld2"; op)
+        @test op == load("testopempty.jld2", "op")
+    end
 end