Support loading workload sets from different feature bands

Author: dsplaisted

src/Cli/dotnet/commands/dotnet-workload/install/WorkloadManifestUpdater.cs

@@ -264,7 +264,7 @@ private IEnumerable<ManifestVersionUpdate> CalculateManifestRollbacks(IEnumerabl
                 var (id, (version, band)) = manifest;
                 var (installedVersion, installedBand) = GetInstalledManifestVersion(id);
                 return new ManifestVersionUpdate(id, installedVersion, installedBand.ToString(), version, band.ToString());
-            });
+            }).ToList();    //  Call ToList() so that GetInstalledManifestVersion call isn't delayed until the result is iterated over
         }
 
         public async Task<IEnumerable<WorkloadDownload>> GetManifestPackageDownloadsAsync(bool includePreviews, SdkFeatureBand providedSdkFeatureBand, SdkFeatureBand installedSdkFeatureBand)

src/Resolvers/Microsoft.NET.Sdk.WorkloadManifestReader/SdkDirectoryWorkloadManifestProvider.cs

@@ -124,10 +124,32 @@ public void RefreshWorkloadManifests()
             _useManifestsFromInstallState = true;
             var availableWorkloadSets = GetAvailableWorkloadSets();
 
+            bool TryGetWorkloadSet(string workloadSetVersion, out WorkloadSet? workloadSet)
+            {
+                if (availableWorkloadSets.TryGetValue(workloadSetVersion, out workloadSet))
+                {
+                    return true;
+                }
+
+                //  Check to see if workload set is from a different feature band
+                WorkloadSet.WorkloadSetVersionToWorkloadSetPackageVersion(workloadSetVersion, out SdkFeatureBand workloadSetFeatureBand);
+                if (!workloadSetFeatureBand.Equals(_sdkVersionBand))
+                {
+                    var featureBandWorkloadSets = GetAvailableWorkloadSets(workloadSetFeatureBand);
+                    if (featureBandWorkloadSets.TryGetValue(workloadSetVersion, out workloadSet))
+                    {
+                        return true;
+                    }
+                }
+
+                workloadSet = null;
+                return false;
+            }
+
             if (_workloadSetVersionFromConstructor != null)
             {
                 _useManifestsFromInstallState = false;
-                if (!availableWorkloadSets.TryGetValue(_workloadSetVersionFromConstructor, out _workloadSet))
+                if (!TryGetWorkloadSet(_workloadSetVersionFromConstructor, out _workloadSet))
                 {
                     throw new FileNotFoundException(string.Format(Strings.WorkloadVersionNotFound, _workloadSetVersionFromConstructor));
                 }
@@ -139,7 +161,7 @@ public void RefreshWorkloadManifests()
                 if (_globalJsonWorkloadSetVersion != null)
                 {
                     _useManifestsFromInstallState = false;
-                    if (!availableWorkloadSets.TryGetValue(_globalJsonWorkloadSetVersion, out _workloadSet))
+                    if (!TryGetWorkloadSet(_globalJsonWorkloadSetVersion, out _workloadSet))
                     {
                         _exceptionToThrow = new FileNotFoundException(string.Format(Strings.WorkloadVersionFromGlobalJsonNotFound, _globalJsonWorkloadSetVersion, _globalJsonPathFromConstructor));
                         return;
@@ -155,7 +177,7 @@ public void RefreshWorkloadManifests()
                     var installState = InstallStateContents.FromPath(installStateFilePath);
                     if (!string.IsNullOrEmpty(installState.WorkloadVersion))
                     {
-                        if (!availableWorkloadSets.TryGetValue(installState.WorkloadVersion!, out _workloadSet))
+                        if (!TryGetWorkloadSet(installState.WorkloadVersion!, out _workloadSet))
                         {
                             throw new FileNotFoundException(string.Format(Strings.WorkloadVersionFromInstallStateNotFound, installState.WorkloadVersion, installStateFilePath));
                         }
@@ -446,18 +468,24 @@ void ProbeDirectory(string manifestDirectory, string featureBand)
         /// </summary>
         public Dictionary<string, WorkloadSet> GetAvailableWorkloadSets()
         {
+            return GetAvailableWorkloadSets(_sdkVersionBand);
+        }
+
+        public Dictionary<string, WorkloadSet> GetAvailableWorkloadSets(SdkFeatureBand workloadSetFeatureBand)
+        {
+            //  How to deal with cross-band workload sets?
             Dictionary<string, WorkloadSet> availableWorkloadSets = new Dictionary<string, WorkloadSet>();
 
             foreach (var manifestRoot in _manifestRoots.Reverse())
             {
-                //  Workload sets must match the SDK feature band, we don't support any fallback to a previous band
-                var workloadSetsRoot = Path.Combine(manifestRoot, _sdkVersionBand.ToString(), WorkloadSetsFolderName);
+                //  We don't automatically fall back to a previous band
+                var workloadSetsRoot = Path.Combine(manifestRoot, workloadSetFeatureBand.ToString(), WorkloadSetsFolderName);
                 if (Directory.Exists(workloadSetsRoot))
                 {
                     foreach (var workloadSetDirectory in Directory.GetDirectories(workloadSetsRoot))
                     {
                         var workloadSetVersion = Path.GetFileName(workloadSetDirectory);
-                        var workloadSet = WorkloadSet.FromWorkloadSetFolder(workloadSetDirectory, workloadSetVersion, _sdkVersionBand);
+                        var workloadSet = WorkloadSet.FromWorkloadSetFolder(workloadSetDirectory, workloadSetVersion, workloadSetFeatureBand);
                         availableWorkloadSets[workloadSet.Version!] = workloadSet;
                     }
                 }