grib2: "Grib2_Statistical_Process_Type" attribute has "UnknownStatType--1" for non-interval products

[cambecc]

Versions impacted by the bug

5.10.0
5.11.0 SNAPSHOT

What went wrong?

A GRIB2 Variable with no time intervals always has a Grib2_Statistical_Process_Type attribute with the value UnknownStatType--1. (This happens because the string format is "UnknownStatType-%d" and the substitution is -1).

Although a minor issue, it's annoying and can cause confusion. I first thought this was out of date lookup tables, then concluded UnknownStatType--1 is (unintentionally) a special string which means "no intervals".

The description of unrelated issue #730 shows exactly this happening.

Relevant log messages

No response

If you have an example file that you can share, please attach it to this issue.

If so, may we include it in our test datasets to help ensure the bug does not return once fixed?
Note: the test datasets are publicly accessible without restriction.

No

Code of Conduct

• I agree to follow the UCAR/Unidata Code of Conduct

[cambecc]

I have a fix for this, but wondering if there are any compatibility concerns.

[lesserwhirls]

Yep, that's a bit annoying and confusing. I think it makes sense to exclude the Grib2_Statistical_Process_Type attribute in these cases, and I think that's the intent with the if statement here:

netcdf-java/grib/src/main/java/ucar/nc2/grib/collection/Grib2Collection.java

Lines 276 to 279 in a4c25ab

	String statType = cust2.getStatisticName(vindex.getIntvType());
	if (statType != null) {
	v.addAttribute(new Attribute("Grib2_Statistical_Process_Type", statType));
	}

I don't foresee its removal in these cases causing any compatibility concerns.