Support reshaping custom 0-dimensional arrays (#26870)

Fixes #26163.

base/reshapedarray.jl

@@ -168,6 +168,11 @@ function __reshape(p::Tuple{AbstractArray,IndexCartesian}, dims::Dims)
     ReshapedArray(parent, dims, reverse(mi))
 end
 
+function __reshape(p::Tuple{AbstractArray{<:Any,0},IndexCartesian}, dims::Dims)
+    parent = p[1]
+    ReshapedArray(parent, dims, ())
+end
+
 function __reshape(p::Tuple{AbstractArray,IndexLinear}, dims::Dims)
     parent = p[1]
     ReshapedArray(parent, dims, ())

test/arrayops.jl

@@ -189,6 +189,22 @@ end
     end
 end
 
+struct Z26163 <: AbstractArray{Int,0}; end
+Base.size(::Z26163) = ()
+Base.getindex(::Z26163) = 0
+struct V26163 <: AbstractArray{Int,1}; end
+Base.size(::V26163) = (1,)
+Base.getindex(::V26163, ::Int) = 0
+@testset "reshape of custom zero- and one-dimensional arrays" begin
+    z = Z26163()
+    v = V26163()
+    @test z == reshape(v, ()) == fill(0, ())
+    @test reshape(z, 1) == v == [0]
+    @test reshape(z, 1, 1) == reshape(v, 1, 1) == fill(0, 1, 1)
+    @test occursin("1-element reshape", summary(reshape(z, 1)))
+    @test_broken occursin("0-dimensional reshape", summary(reshape(v, ())))
+end
+
 @test reshape(1:5, (5,)) === 1:5
 @test reshape(1:5, 5) === 1:5
 

test/strings/io.jl

@@ -144,7 +144,8 @@
     end
 end
 @testset "join()" begin
-    @test join([]) == ""
+    @test join([]) == join([],",") == ""
+    @test_broken join(()) == join((),",") == ""
     @test join(["a"],"?") == "a"
     @test join("HELLO",'-') == "H-E-L-L-O"
     @test join(1:5, ", ", " and ") == "1, 2, 3, 4 and 5"