Installing three-letter ISO localized packages are not compatible.

[JonDouglas]

Details about Problem

When installing any package that has been localized with resource assemblies & contains a three-letter ISO name, it will fail to install.

https://docs.microsoft.com/en-us/nuget/create-packages/creating-localized-packages

NuGet product used (NuGet.exe | Visual Studio | MSBuild.exe | dotnet.exe):

16.9, dotnet SDK 5.0.202

Worked before? If so, with which NuGet version:

N/A, but does work with 2 letter locale packages such as zh-CN (i.e. https://www.nuget.org/packages/Humanizer.Core.zh-CN/2.9.7)

Repro steps and/or sample project

1. Create a .NET 5 console application
2. Install https://www.nuget.org/packages/Humanizer.Core.fil-PH/2.9.7
3. Error

Running restore with 8 concurrent jobs.
Reading project file C:\Users\Jon-Personal\source\repos\ConsoleApp12\ConsoleApp12\ConsoleApp12.csproj.
Restoring packages for C:\Users\Jon-Personal\source\repos\ConsoleApp12\ConsoleApp12\ConsoleApp12.csproj...
Restoring packages for .NETCoreApp,Version=v5.0...
Resolving conflicts for net5.0...
Checking compatibility of packages on net5.0.
Checking compatibility for ConsoleApp12 1.0.0 with net5.0.
Checking compatibility for Newtonsoft.Json 13.0.1 with net5.0.
Checking compatibility for System.Linq.Dynamic 1.0.8 with net5.0.
Checking compatibility for Humanizer.Core.fil-PH 2.9.7 with net5.0.
Checking compatibility for Humanizer.Core 2.9.7 with net5.0.
Incompatible packages: 1
NU1701: Package 'System.Linq.Dynamic 1.0.8' was restored using '.NETFramework,Version=v4.6.1, .NETFramework,Version=v4.6.2, .NETFramework,Version=v4.7, .NETFramework,Version=v4.7.1, .NETFramework,Version=v4.7.2, .NETFramework,Version=v4.8' instead of the project target framework 'net5.0'. This package may not be fully compatible with your project.
NU1202: Package Humanizer.Core.fil-PH 2.9.7 is not compatible with net5.0 (.NETCoreApp,Version=v5.0). Package Humanizer.Core.fil-PH 2.9.7 does not support any target frameworks.
Package restore failed. Rolling back package changes for 'ConsoleApp12'.
Time Elapsed: 00:00:00.0547089
========== Finished ==========

1. Create a dotnet new .NET 5 console application
2. Install https://www.nuget.org/packages/Humanizer.Core.fil-PH/2.9.7
3. Error:

dotnet add package Humanizer.Core.fil-PH
  Determining projects to restore...
  Writing C:\Users\Jon-Personal\AppData\Local\Temp\tmpF27F.tmp
info : Adding PackageReference for package 'Humanizer.Core.fil-PH' into project 'C:\Users\Jon-Personal\source\repos\ConsoleApp12\ConsoleApp12\ConsoleApp12.csproj'.
info :   CACHE https://api.nuget.org/v3/registration5-gz-semver2/humanizer.core.fil-ph/index.json
info : Restoring packages for C:\Users\Jon-Personal\source\repos\ConsoleApp12\ConsoleApp12\ConsoleApp12.csproj...
warn : NU1701: Package 'System.Linq.Dynamic 1.0.8' was restored using '.NETFramework,Version=v4.6.1, .NETFramework,Version=v4.6.2, .NETFramework,Version=v4.7, .NETFramework,Version=v4.7.1, .NETFramework,Version=v4.7.2, .NETFramework,Version=v4.8' instead of the project target framework 'net5.0'. This package may not be fully compatible with your project.
error: NU1202: Package Humanizer.Core.fil-PH 2.9.7 is not compatible with net5.0 (.NETCoreApp,Version=v5.0). Package Humanizer.Core.fil-PH 2.9.7 does not support any target frameworks.
error: Package 'Humanizer.Core.fil-PH' is incompatible with 'all' frameworks in project 'C:\Users\Jon-Personal\source\repos\ConsoleApp12\ConsoleApp12\ConsoleApp12.csproj'.

Investigation

https://docs.microsoft.com/en-us/dotnet/api/system.globalization.cultureinfo?view=net-5.0#culture-names-and-identifiers has some interesting cases around availability of two-letter vs. three-letter.

https://stackoverflow.com/a/21042311/1048571 seems to suggest that CultureInfo limitations too. The list https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes doesn’t include fil in it. However 639-2 & 639-3 do include it.

The format for the culture name based on RFC 4646 is languagecode2>-country/regioncode2, where languagecode2 is the two-letter language code and country/regioncode2 is the two-letter subculture code. Examples include ja-JP for Japanese (Japan) and en-US for English (United States). In cases where a two-letter language code is not available, a three-letter code derived from ISO 639-2 is used.

InvariantCulture should handle this however? I’m not aware of any specific code in NuGet that limits as this fails in both VS & dotnet CLI which have different compat code for installing.

[nkolev92]

I think there's a dup in #2245.

@kartheekp-ms can you please verify.

[nkolev92]

Triage: @jebriede can you please take a look.

[aortiz-msft]

@v-luzh - does this work on NuGet 5.8 or earlier?

[v-luzh]

@aortiz-msft it repro on VS D16.8\30420.98 with implicit NuGet 5.8.0.6776 as below screenshot, but the difference is it didn't show error NU1701.

[nkolev92]

Closing as dup of #2245

[clairernovotny]

Why was this closed as a dup? Seems like a different issue with three letter locales? This is preventing certain locales from working:

Humanizr/Humanizer#1057

[MarkIvanDev]

This is still a problem today. I hope there is a fix to support three-letter locales.

[ChandraTang]

@JonDouglas can this be re-opened? This still a problem after three years. @nkolev92 had pointed out the issue in another issue (I missed the link) is here
https://github.com/NuGet/NuGet.Client/blob/84d99ce064a5f70628c89af9f30693581e84dc37/src/NuGet.Core/NuGet.Packaging/ContentModel/ManagedCodeConventions.cs#L143-L164