fix(arrow/scalar): handle zero-length scalar arrays

arrow/scalar/scalar.go

@@ -771,6 +771,26 @@ func MakeArrayFromScalar(sc Scalar, length int, mem memory.Allocator) (arrow.Arr
 		return nil, fmt.Errorf("%w: array length must be non-negative, got %d", arrow.ErrInvalid, length)
 	}
 
+	if length == 0 {
+		if dt, ok := sc.DataType().(*arrow.RunEndEncodedType); ok {
+			runEndsBuilder := array.NewBuilder(mem, dt.RunEnds())
+			defer runEndsBuilder.Release()
+			runEnds := runEndsBuilder.NewArray()
+			defer runEnds.Release()
+
+			valuesBuilder := array.NewBuilder(mem, dt.Encoded())
+			defer valuesBuilder.Release()
+			values := valuesBuilder.NewArray()
+			defer values.Release()
+
+			return array.NewRunEndEncodedArray(runEnds, values, 0, 0), nil
+		}
+
+		builder := array.NewBuilder(mem, sc.DataType())
+		defer builder.Release()
+		return builder.NewArray(), nil
+	}
+
 	if !sc.IsValid() {
 		return MakeArrayOfNull(sc.DataType(), length, mem), nil
 	}

arrow/scalar/scalar_test.go

@@ -1349,6 +1349,33 @@ func TestMakeArrayFromScalarUsesCorrectBinaryOffsetWidthForNulls(t *testing.T) {
 	}
 }
 
+func TestMakeArrayFromScalarSupportsZeroLength(t *testing.T) {
+	mem := memory.NewCheckedAllocator(memory.NewGoAllocator())
+	defer mem.AssertSize(t, 0)
+
+	for _, s := range getScalars(mem) {
+		t.Run(s.DataType().Name(), func(t *testing.T) {
+			if releasable, ok := s.(scalar.Releasable); ok {
+				defer releasable.Release()
+			}
+
+			arr, err := scalar.MakeArrayFromScalar(s, 0, mem)
+			require.NoError(t, err)
+			defer arr.Release()
+			assert.Equal(t, 0, arr.Len())
+			assert.Equal(t, 0, arr.NullN())
+			require.NoError(t, array.ValidateFull(arr))
+		})
+	}
+
+	nullArr, err := scalar.MakeArrayFromScalar(scalar.ScalarNull, 0, mem)
+	require.NoError(t, err)
+	defer nullArr.Release()
+	assert.Equal(t, 0, nullArr.Len())
+	assert.Equal(t, 0, nullArr.NullN())
+	require.NoError(t, array.ValidateFull(nullArr))
+}
+
 func TestMakeArrayFromScalarRejectsNegativeLength(t *testing.T) {
 	mem := memory.NewCheckedAllocator(memory.NewGoAllocator())
 	defer mem.AssertSize(t, 0)