Cannot load data when duplicate variable in output

[jk-rieck]

xmitgcm.open_mdsdataset() fails with ValueError: dimensions ('time', 'j', 'i') must have the same length as the number of data dimensions, ndim=2 if the field to read has a duplicate variable, i.e. the user has defined a variable twice to the same file in data.diagnostics. For example if I define fields(1:2,1) = 'UVEL', 'UVEL',, xmitgcm cannot read the resulting model output.

Admittedly, this is not really a big issue as the case that results in the error is not a useful one. However, an error message could maybe be implemented so the user knows immediately what's wrong. Or would it make more sense to not allow the diagnostics package to write the same variable multiple times to the same file?

[rabernat]

Thanks for the issue. I believe this is very closely related to #286.

[jk-rieck]

A behavior like in #286 would actually be almost a feature for this issue. At least the case in #286 does not raise an error and in the end the variable is in the dataset. The difference between the two issues is that in #286 the variable with the same name/id is present in two separate files, while in #287 it is present twice in the same file.