From 87b1a364fb0b803e4a6ba070e20cce31bae9baf7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bogumi=C5=82=20Kami=C5=84ski?= <bkamins@sgh.waw.pl>
Date: Sat, 17 Aug 2024 07:37:12 +0200
Subject: [PATCH] fix vcat type piracy

---
 src/abstractdataframe/abstractdataframe.jl | 4 ++++
 test/cat.jl                                | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/src/abstractdataframe/abstractdataframe.jl b/src/abstractdataframe/abstractdataframe.jl
index e8f4e32ed0..65635a76bb 100644
--- a/src/abstractdataframe/abstractdataframe.jl
+++ b/src/abstractdataframe/abstractdataframe.jl
@@ -1956,6 +1956,10 @@ Base.reduce(::typeof(vcat),
             init::AbstractDataFrame=DataFrame()) =
     reduce(vcat, collect(AbstractDataFrame, dfs), cols=cols, source=source, init=init)
 
+# definition fixing type piracy
+Base.reduce(op::typeof(vcat), A::AbstractVector{Union{}}; kw...) =
+    mapreduce(identity, op, A; kw...)
+
 function _vcat(dfs::AbstractVector{AbstractDataFrame};
                cols::Union{Symbol, AbstractVector{Symbol},
                            AbstractVector{<:AbstractString}}=:setequal)
diff --git a/test/cat.jl b/test/cat.jl
index b5aa1cfd9b..5f45230e98 100644
--- a/test/cat.jl
+++ b/test/cat.jl
@@ -477,4 +477,9 @@ end
     @test reduce(vcat, (df1, df2)) == DataFrame(a=[1, 1], b=[2, 2])
 end
 
+@testset "vcat type piracy" begin
+    x = Int[]
+    @test reduce(vcat, Union{}[], init=x) === x
+end
+
 end # module