Support package@version syntax in dotnet new install, partial fix for #45422 (#45545)

Progress towards #45422

This adds support for package@version syntax without removing support for package::version syntax. I'll add a follow-up PR in main to add a warning, and then we can remove support for package::version syntax in .NET 11.

Author: Forgind

src/Cli/Microsoft.TemplateEngine.Cli/TemplatePackageCoordinator.cs

@@ -208,9 +208,9 @@ internal async Task<NewCommandStatus> EnterInstallFlowAsync(InstallCommandArgs a
 
             foreach (string installArg in args.TemplatePackages)
             {
-                string[] splitByColons = installArg.Split(new[] { "::" }, StringSplitOptions.RemoveEmptyEntries);
-                string identifier = splitByColons[0];
-                string? version = splitByColons.Length > 1 ? splitByColons[1] : null;
+                string[] split = installArg.Split(["::"], StringSplitOptions.RemoveEmptyEntries).SelectMany(arg => arg.Split('@', StringSplitOptions.RemoveEmptyEntries)).ToArray();
+                string identifier = split[0];
+                string? version = split.Length > 1 ? split[1] : null;
                 foreach (string expandedIdentifier in InstallRequestPathResolution.ExpandMaskedPath(identifier, _engineEnvironmentSettings))
                 {
                     installRequests.Add(new InstallRequest(expandedIdentifier, version, details: details, force: args.Force));

test/dotnet-new.Tests/DotnetNewInstallTests.cs

@@ -42,21 +42,22 @@ public void CanInstallRemoteNuGetPackage(string commandName)
         }
 
         [Theory]
-        [InlineData("-i")]
-        [InlineData("install")]
-        public void CanInstallRemoteNuGetPackage_LatestVariations(string commandName)
+        [InlineData("::")]
+        [InlineData("@")]
+        public void CanInstallRemoteNuGetPackage_LatestVariations(string separator)
         {
+            var commandName = "install";
             CommandResult command1 = new DotnetNewCommand(_log, commandName, "Microsoft.DotNet.Common.ProjectTemplates.5.0")
                 .WithCustomHive(CreateTemporaryFolder(folderName: "Home"))
                 .WithWorkingDirectory(CreateTemporaryFolder())
                 .Execute();
 
-            CommandResult command2 = new DotnetNewCommand(_log, commandName, "Microsoft.DotNet.Common.ProjectTemplates.5.0::")
+            CommandResult command2 = new DotnetNewCommand(_log, commandName, $"Microsoft.DotNet.Common.ProjectTemplates.5.0{separator}")
                 .WithCustomHive(CreateTemporaryFolder(folderName: "Home"))
                 .WithWorkingDirectory(CreateTemporaryFolder())
                 .Execute();
 
-            CommandResult command3 = new DotnetNewCommand(_log, commandName, "Microsoft.DotNet.Common.ProjectTemplates.5.0::*")
+            CommandResult command3 = new DotnetNewCommand(_log, commandName, $"Microsoft.DotNet.Common.ProjectTemplates.5.0{separator}*")
                 .WithCustomHive(CreateTemporaryFolder(folderName: "Home"))
                 .WithWorkingDirectory(CreateTemporaryFolder())
                 .Execute();