What's wrong with "conflicting" _FillValue and missing_value?

[dopplershift]

So this exception:

ValueError: Conflicting _FillValue and missing_value attrs on a variable 'MergedBaseReflectivityQC_altitude_above_msl': -999.0 vs. -99.0

Consider opening the offending dataset using decode_cf=False, correcting the attrs and decoding explicitly using xarray.decode_cf().

Why is having _FillValue and missing_value different considered an error in decoding CF? It's perfectly CF-compliant, especially since _FillValue is a scalar (used by the netCDF library to initialize an array), and missing_value can be a vector (representing one or more undefined or invalid values).

This happens in this case because the source GRIB file has one value specified for "missing" (maps to missing_value) and another for "no coverage" (which has been mapped to _FillValue).

Is this a technical limitation? Or just something that needs an implementation?

[shoyer]

This is the same issue as #1749. Based on that discussion, I think it just needs a fix.

[dopplershift]

Somehow managed to forget about an issue I was previously involved with. Lovely. Closing in favor of that issue.