Fix zero-dim view! (ITensor#149)

Author: mtfishman

Project.toml

@@ -1,7 +1,7 @@
 name = "BlockSparseArrays"
 uuid = "2c9a651f-6452-4ace-a6ac-809f4280fbb4"
 authors = ["ITensor developers <[email protected]> and contributors"]
-version = "0.7.13"
+version = "0.7.14"
 
 [deps]
 Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"

src/BlockArraysExtensions/BlockArraysExtensions.jl

@@ -561,6 +561,11 @@ function view!(a::AbstractArray{<:Any,N}, index::Vararg{Block{1},N}) where {N}
   blocks(a)[Int.(index)...] = blocks(a)[Int.(index)...]
   return blocks(a)[Int.(index)...]
 end
+# Fix ambiguity error.
+function view!(a::AbstractArray{<:Any,0})
+  blocks(a)[] = blocks(a)[]
+  return blocks(a)[]
+end
 
 function view!(a::AbstractArray{<:Any,N}, index::BlockIndexRange{N}) where {N}
   # TODO: Is there a better code pattern for this?

test/test_basics.jl

@@ -39,7 +39,8 @@ using BlockSparseArrays:
 using GPUArraysCore: @allowscalar
 using JLArrays: JLArray, JLMatrix
 using LinearAlgebra: Adjoint, Transpose, dot, norm, tr
-using SparseArraysBase: SparseArrayDOK, SparseMatrixDOK, SparseVectorDOK, storedlength
+using SparseArraysBase:
+  SparseArrayDOK, SparseMatrixDOK, SparseVectorDOK, isstored, storedlength
 using Test: @test, @test_broken, @test_throws, @testset, @inferred
 using TestExtras: @constinferred
 using TypeParameterAccessors: TypeParameterAccessors, Position
@@ -1159,6 +1160,24 @@ arrayts = (Array, JLArray)
       @test view!(a, blk...) == x
       @test @view!(a[blk...]) == x
     end
+    # 0-dim case
+    # Regression test for https://github.com/ITensor/BlockSparseArrays.jl/issues/148
+    for I in ((), (Block(),))
+      a = dev(BlockSparseArray{elt}(undef))
+      @test !isstored(a)
+      @test iszero(blockstoredlength(a))
+      @test isempty(eachblockstoredindex(a))
+      @test iszero(a)
+      b = @view! a[I...]
+      @test isstored(a)
+      @test isone(blockstoredlength(a))
+      @test issetequal(eachblockstoredindex(a), [Block()])
+      @test iszero(adapt(Array)(a))
+      @test b isa arrayt{elt,0}
+      @test size(b) == ()
+      # Converting to `Array` works around a bug in `iszero(JLArray{Float64}(undef))`.
+      @test iszero(adapt(Array)(b))
+    end
   end
   @testset "LinearAlgebra" begin
     a1 = dev(BlockSparseArray{elt}(undef, [2, 3], [2, 3]))