NuGet Package being marked as prerelease - nuget

Question

I have built a NuGet Package and uploaded it to a locally hosted Sonatype Nexus repository.
I have given it the version 0.1.1+251019-020007-e3baff. My understanding of sem-ver 2.0 is this should be treated as a stable/release version (because the data after the + should only be treated as metadata), but nuget seems to be getting confused and showing it only if I include prerelease versions in the search.
For example in the cli if I run Find-package <my-package-name> I get no results. But if I run Find-Package -prerelease <my-package-name> I get
Id Versions Description
-- -------- -----------
<my-package> {0.1.1} <description>
Likewise if I use the GUI in Visual Studio I have to check the "include prerelease" option, but then the version that is available is marked as "latest stable"...
In Nexus there is a flag "is_prerelease" that is being set to true by something, not sure what, Is that flag being incorrectly set and then being used in the search?
Is there something else I am doing wrong? Is my understanding of the + character in sem-ver 2.0 not correct?
I am using NuGet version 4.9.3, and nexus is version 3.19.0-01

Answer 1

NuGet's logic is available as packages, the versioning logic in the NuGet.Versioning package. Using this little program:
static void Main(string[] args)
{
var version = NuGetVersion.Parse("0.1.1+251019-020007-e3baff");
Console.WriteLine($"Version is prerelease: {version.IsPrerelease}");
}
I get the output
Version is prerelease: False
I tried many versions of the NuGet.Versioning package, from the latest 5.3.1, to 4.9.4, 4.3.0, 3.5.0, 3.2.0 and even the oldest release version of the package, 1.0.1. All of them say that your version is not prerelease.
Therefore, it's not NuGet that thinks your package is prerelease. Given that - is the separator for prerelease labels, my guess is that Nexus is incorrectly doing a simple check similar to version.Contains('-') to determine if it's pre-release. This is a shame, as semver.org has two regex expressions on their website which do not have this behaviour (example, I have no idea how long this link will be valid). If your Nexus installation isn't running the latest version, I suggest trying to update if you can. If it's still a problem, you could try contacting the software vendor to report a bug.
As a work around, you could try avoid using the - character in the build metadata as long as you keep using Nexus. SemVer2 is quite restricted in the characters it lets you use, so I suggest using . instead (0.1.1+251019.020007.e3baff).