fixed binary ops between LArray and scalar Groups which silently gave wrong results (closes #797)

Author: gdementen

doc/source/changes/version_0_31.rst.inc

@@ -33,6 +33,9 @@ Miscellaneous improvements
 Fixes
 ^^^^^
 
+* fixed binary operations (+, -, *, etc.) between an LArray and a (scalar) Group which silently gave a wrong
+  result (closes :issue:`797`).
+
 * fixed taking a subset of an array with boolean labels for an axis if the user explicitly specify the axis
   (closes :issue:`735`). When the user does not specify the axis, it currently fails but it is unclear what to do in
   that case (see :issue:`794`).

larray/core/array.py

@@ -5476,6 +5476,13 @@ def opmethod(self, other):
             if isinstance(other, ExprNode):
                 other = other.evaluate(self.axes)
 
+            # XXX: unsure what happens for non scalar Groups.
+            #      we might want to be more general than this and .eval all Groups?
+            #      or (and I think it's better) define __larray__ on Group
+            #      so that a non scalar Group acts like an Axis in this situation.
+            if isinstance(other, Group) and np.isscalar(other.key):
+                other = other.eval()
+
             # we could pass scalars through aslarray too but it is too costly performance-wise for only suppressing one
             # isscalar test and an if statement.
             # TODO: ndarray should probably be converted to larrays because that would harmonize broadcasting rules, but

larray/tests/test_array.py

@@ -2733,6 +2733,14 @@ def test_broadcasting_no_name():
         np.asarray(a) * np.asarray(c)
 
 
+def test_binary_ops_with_scalar_group():
+    time = Axis('time=2015..2019')
+    arr = ndtest(3)
+    expected = arr + 2015
+    assert_larray_equal(time.i[0] + arr, expected)
+    assert_larray_equal(arr + time.i[0], expected)
+
+
 def test_unary_ops(small_array):
     raw = small_array.data