simple assignment gives MergeError

[jklymak]

On xarray 0.20.1

If I make a simple Dataset and try to assign to a variable I now get an error:

dat = xr.Dataset(coords=dict(x=np.linspace(0,10., 100)),
                 data_vars=dict(thedata=('x', np.zeros(100))))
dat['thedata'] = np.arange(100)

MergeError: unable to determine if these variables should be coordinates or not in the merged result: {'thedata'}

Of course I can do:

dat['thedata'] = ('x', np.arange(100))

or

dat['thedata'].values = np.arange(100)

or

dat['thedata'][:] = np.arange(100)

all work fine. However, I do not remember this as being necessary, nor do I think they should be if the RHS has the right dimensions and is a bare numpy array...

[jklymak]

OK, I take it back, I guess the simple assignment never worked, or at least not as far back as I'd care to check (0.10.3).

I guess I understand why this happens - xarray doesn't know if I want dat['thedata'] to be a new variable or to fill the old one. However, I'm not sure what harm would be done by letting the assignment work without indexing if the alternative is a failed merge.