`DotNetClassicTool` incompatible with central package management

[bgrainger]

Switch a project using Faithlife.Build to central package management.

After you do, DotNetClassicTool.TryCreateFrom fails, because the <PackageReference> element no longer has a @Version attribute. Failing code is:

FaithlifeBuild/src/Faithlife.Build/DotNetClassicTool.cs

Lines 53 to 57 in f61b0b0

	var packageVersion = ((IEnumerable) XDocument.Load(projectPath).XPathEvaluate("//PackageReference"))
	.OfType<XElement>()
	.Where(x => string.Equals(x.Attribute("Include")?.Value, packageName, StringComparison.OrdinalIgnoreCase))
	.Select(x => x.Attribute("Version")?.Value)
	.FirstOrDefault();

An example project that repros the bug is https://github.com/bgrainger/CentrallyManagedTool.

One solution would be to hard-code checks for Directory.Packages.props and look there for the version, but also respect @VersionOverride etc. However, it seems less brittle to use MSBuild to parse the project file and resolve the version to use.

Based on dotnet outdated, one way to do this is to shell out to MSBuild, then parse the JSON it produces: https://github.com/dotnet-outdated/dotnet-outdated/blob/782521a01639e4387dd6b3fa36f8e25cd279f137/src/DotNetOutdated.Core/Services/DependencyGraphService.cs#L28

Here's sample output from msbuild CentrallyManagedTool.csproj /t:Restore,GenerateRestoreGraphFile /p:RestoreGraphOutputPath=X:\Temp\graph.json. Note that it appears that one would need to parse version ranges that look like "NUnit.ConsoleRunner": "[3.15.2, )" in order to find a range of versions that might be installed. I don't know if there's a way to resolve it to the version that actually would get restored?

{
  "format": 1,
  "restore": {
    "X:\\CentrallyManagedTool\\CentrallyManagedTool.csproj": {}
  },
  "projects": {
    "X:\\CentrallyManagedTool\\CentrallyManagedTool.csproj": {
      "version": "1.0.0",
      "restore": {
        "projectUniqueName": "X:\\CentrallyManagedTool\\CentrallyManagedTool.csproj",
        "projectName": "CentrallyManagedTool",
        "projectPath": "X:\\CentrallyManagedTool\\CentrallyManagedTool.csproj",
        "packagesPath": "X:\\Users\\me\\.nuget\\packages\\",
        "outputPath": "X:\\CentrallyManagedTool\\obj\\",
        "projectStyle": "PackageReference",
        "centralPackageVersionsManagementEnabled": true,
        "fallbackFolders": [
          "C:\\Program Files\\dotnet\\sdk\\NuGetFallbackFolder"
        ],
        "configFilePaths": [
          "X:\\CentrallyManagedTool\\NuGet.Config",
          "X:\\Users\\me\\AppData\\Roaming\\NuGet\\NuGet.Config",
          "C:\\Program Files (x86)\\NuGet\\Config\\Microsoft.VisualStudio.Offline.config"
        ],
        "originalTargetFrameworks": [
          "net6.0"
        ],
        "sources": {
          "C:\\Program Files (x86)\\Microsoft SDKs\\NuGetPackages\\": {},
          "F:\\Packages": {},
          "https://api.nuget.org/v3/index.json": {},
          "https://pkgs.dev.azure.com/Faithlife/Packages/_packaging/main/nuget/v2": {}
        },
        "frameworks": {
          "net6.0": {
            "targetAlias": "net6.0",
            "projectReferences": {}
          }
        },
        "warningProperties": {
          "warnAsError": [
            "NU1605"
          ]
        }
      },
      "frameworks": {
        "net6.0": {
          "targetAlias": "net6.0",
          "dependencies": {
            "Faithlife.Build": {
              "target": "Package",
              "version": "[5.14.7, )",
              "versionCentrallyManaged": true
            },
            "NUnit.ConsoleRunner": {
              "target": "Package",
              "version": "[3.15.2, )",
              "versionCentrallyManaged": true
            }
          },
          "centralPackageVersions": {
            "Faithlife.Build": "[5.14.7, )",
            "NUnit.ConsoleRunner": "[3.15.2, )"
          },
          "imports": [
            "net461",
            "net462",
            "net47",
            "net471",
            "net472",
            "net48",
            "net481"
          ],
          "assetTargetFallback": true,
          "warn": true,
          "frameworkReferences": {
            "Microsoft.NETCore.App": {
              "privateAssets": "all"
            }
          },
          "runtimeIdentifierGraphPath": "C:\\Program Files\\dotnet\\sdk\\6.0.402\\RuntimeIdentifierGraph.json"
        }
      }
    }
  }
}

[ejball]

It's definitely a hack. I'd like to think DotNetClassicTool would be rarely used, given that .NET tools are the new hotness. Adding another hack to support "normal" central package management might be simplest, but I have no objection to something more complex and correct if it's non-breaking.