fix: can't assume that time/baseline ordering means rectangularity

Author: steven-murray

src/pyuvdata/utils/bltaxis.py

@@ -193,6 +193,12 @@ def determine_rectangularity(
     or Nbls will give you either all the same time and all different baselines, or
     vice versa. This does NOT require that the baselines and times are sorted within
     that structure.
+
+    Note that blt_order being (time, baseline) or vice versa does *not* guarantee
+    rectangularity, even when Nblts == Nbls * Ntimes, since if `autos_first = True` is
+    set on `reorder_blts`, then it will still set the blt_order attribute to
+    (time, baseline), but they will not strictly be in that order (since it will
+    actually be in autos first order).
     """
     # check if the data is rectangular
     time_first = True
@@ -204,10 +210,13 @@ def determine_rectangularity(
         return True, True
     elif ntimes == 1:
         return True, False
+    # Note that the opposite isn't true: time/baseline ordering does not always mean
+    # that we have rectangularity, because of the autos_first keyword to reorder_blts.
     elif blt_order == ("baseline", "time"):
         return True, True
-    elif blt_order == ("time", "baseline"):
-        return True, False
+
+    # elif blt_order == ("time", "baseline"):
+    #     return True, False
 
     # That's all the easiest checks.
     if time_array[1] == time_array[0]:

src/pyuvdata/uvdata/uvdata.py

@@ -4083,6 +4083,15 @@ def reorder_blts(
 
         self.set_rectangularity(force=True)
 
+        print(
+            "blt_ordEr",
+            self.blt_order,
+            self.time_array,
+            self.Ntimes,
+            self.Nbls,
+            self.Nblts,
+            self.blts_are_rectangular,
+        )
         # check if object is self-consistent
         if run_check:
             self.check(