From e544c13785a0473789fd8e7a6bbee1ddce7d3e5a Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Thu, 16 Jan 2025 12:47:03 -0500
Subject: [PATCH] Fix zero-dimensional conversion

---
 Project.toml                        |  2 +-
 src/abstractblocksparsearray/map.jl | 19 +++++++++++++++++--
 test/basics/test_basics.jl          |  7 +++++--
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/Project.toml b/Project.toml
index c7a8b187..11d59835 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "BlockSparseArrays"
 uuid = "2c9a651f-6452-4ace-a6ac-809f4280fbb4"
 authors = ["ITensor developers <support@itensor.org> and contributors"]
-version = "0.2.8"
+version = "0.2.9"
 
 [deps]
 Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"
diff --git a/src/abstractblocksparsearray/map.jl b/src/abstractblocksparsearray/map.jl
index 05529447..52aec400 100644
--- a/src/abstractblocksparsearray/map.jl
+++ b/src/abstractblocksparsearray/map.jl
@@ -1,6 +1,6 @@
 using ArrayLayouts: LayoutArray
 using BlockArrays: blockisequal
-using DerivableInterfaces: @interface, interface
+using DerivableInterfaces: @interface, AbstractArrayInterface, interface
 using LinearAlgebra: Adjoint, Transpose
 using SparseArraysBase: SparseArraysBase, SparseArrayStyle
 
@@ -49,15 +49,30 @@ function reblock(
   return @view parent(a)[map(I -> Vector(I.blocks), parentindices(a))...]
 end
 
+# `map!` specialized to zero-dimensional inputs.
+function map_zero_dim! end
+
+@interface ::AbstractArrayInterface function map_zero_dim!(
+  f, a_dest::AbstractArray, a_srcs::AbstractArray...
+)
+  a_dest[] = f.(map(a_src -> a_src[], a_srcs)...)
+  return a_dest
+end
+
 # TODO: Move to `blocksparsearrayinterface/map.jl`.
 # TODO: Rewrite this so that it takes the blocking structure
 # made by combining the blocking of the axes (i.e. the blocking that
 # is used to determine `union_stored_blocked_cartesianindices(...)`).
 # `reblock` is a partial solution to that, but a bit ad-hoc.
 ## TODO: Make this an `@interface AbstractBlockSparseArrayInterface` function.
-@interface ::AbstractBlockSparseArrayInterface function Base.map!(
+@interface interface::AbstractBlockSparseArrayInterface function Base.map!(
   f, a_dest::AbstractArray, a_srcs::AbstractArray...
 )
+  if iszero(ndims(a_dest))
+    @interface interface map_zero_dim!(f, a_dest, a_srcs...)
+    return a_dest
+  end
+
   a_dest, a_srcs = reblock(a_dest), reblock.(a_srcs)
   for I in union_stored_blocked_cartesianindices(a_dest, a_srcs...)
     BI_dest = blockindexrange(a_dest, I)
diff --git a/test/basics/test_basics.jl b/test/basics/test_basics.jl
index afe403fe..12b3f8aa 100644
--- a/test/basics/test_basics.jl
+++ b/test/basics/test_basics.jl
@@ -187,8 +187,9 @@ arrayts = (Array, JLArray)
       @test iszero(@allowscalar(a[CartesianIndex()]))
       @test a[Block()] == dev(fill(0))
       @test iszero(@allowscalar(a[Block()][]))
-      # Broken:
-      ## @test b[Block()[]] == 2
+      @test @allowscalar(a[Block()[]]) == 0
+      @test Array(a) isa Array{elt,0}
+      @test Array(a) == fill(0)
       for b in (
         (b = copy(a); @allowscalar b[] = 2; b),
         (b = copy(a); @allowscalar b[CartesianIndex()] = 2; b),
@@ -206,6 +207,8 @@ arrayts = (Array, JLArray)
         @test b[Block()] == dev(fill(2))
         @test @allowscalar(b[Block()][]) == 2
         @test @allowscalar(b[Block()[]]) == 2
+        @test Array(b) isa Array{elt,0}
+        @test Array(b) == fill(2)
       end
     end