Add prerelease string when NormalizedVersion doesn't exist (but prelease string does) (#1681)

Author: sean-r-williams

src/code/InstallHelper.cs

@@ -803,7 +803,12 @@ private Hashtable BeginPackageInstall(
             pkgToInstall.RepositorySourceLocation = repository.Uri.ToString();
             pkgToInstall.AdditionalMetadata.TryGetValue("NormalizedVersion", out string pkgVersion);
             if (pkgVersion == null) {
+                // Not all NuGet providers (e.g. Artifactory, possibly others) send NormalizedVersion in NuGet package responses.
+                // If they don't, we need to manually construct the combined version+prerelease from pkgToInstall.Version and the prerelease string.
                 pkgVersion = pkgToInstall.Version.ToString();
+                if (!String.IsNullOrEmpty(pkgToInstall.Prerelease)) {
+                    pkgVersion += $"-{pkgToInstall.Prerelease}";
+                }
             }
             // Check to see if the pkg is already installed (ie the pkg is installed and the version satisfies the version range provided via param)
             if (!_reinstall)