Update MSBuildProject.NuGetPackages APIs to work with packages.config (#619)

This updates INuGetReferences implementation to handle project files using packages.config package references. Also, updated some comments to more clearly explain what the different APIs on that interface do.

Fixes #554

src/common/Microsoft.DotNet.UpgradeAssistant.Abstractions/INuGetReferences.cs

@@ -20,7 +20,7 @@ namespace Microsoft.DotNet.UpgradeAssistant
         IEnumerable<NuGetReference> PackageReferences { get; }
 
         /// <summary>
-        /// Gets the packages that are transitively referenced via other packages or projects for the given <paramref name="tfm"/>.
+        /// Gets all the packages that are referenced for the given <paramref name="tfm"/> either directly or transitively.
         /// </summary>
         /// <param name="tfm">The target framework to get the dependencies for.</param>
         /// <param name="token">A cancellation token.</param>
@@ -28,7 +28,7 @@ namespace Microsoft.DotNet.UpgradeAssistant
         IAsyncEnumerable<NuGetReference> GetTransitivePackageReferencesAsync(TargetFrameworkMoniker tfm, CancellationToken token);
 
         /// <summary>
-        /// Checks if the package name is transitively referenced via other packages or projects.
+        /// Checks if the package name is referenced either directly or transitively via other packages or projects.
         /// </summary>
         /// <param name="packageName">The name of a package.</param>
         /// <param name="token">A cancellation token.</param>
@@ -36,7 +36,9 @@ namespace Microsoft.DotNet.UpgradeAssistant
         ValueTask<bool> IsTransitivelyAvailableAsync(string packageName, CancellationToken token);
 
         /// <summary>
-        /// Checks if the package is transitively referenced via other packages or projects.
+        /// Checks if a particular version of a package is transitively referenced via other packages or projects.
+        /// This does not check whether the package is directly referenced or not and will always return false
+        /// for projects not using PackageReference package references.
         /// </summary>
         /// <param name="nugetReference">The package identity.</param>
         /// <param name="token">A cancellation token.</param>

src/components/Microsoft.DotNet.UpgradeAssistant.MSBuild/MSBuildProject.NuGetPackages.cs

@@ -61,13 +61,19 @@ namespace Microsoft.DotNet.UpgradeAssistant.MSBuild
         }
 
         public IAsyncEnumerable<NuGetReference> GetTransitivePackageReferencesAsync(TargetFrameworkMoniker tfm, CancellationToken token)
-            => GetAllDependenciesAsync(tfm, token).Select(l => new NuGetReference(l.Name, l.Version.ToNormalizedString()));
+            => PackageReferenceFormat switch
+            {
+                NugetPackageFormat.PackageConfig => PackageReferences.ToAsyncEnumerable(),
+                NugetPackageFormat.PackageReference => GetAllPackageReferenceDependenciesAsync(tfm, token).Select(l => new NuGetReference(l.Name, l.Version.ToNormalizedString())),
+                _ => AsyncEnumerable.Empty<NuGetReference>()
+            };
 
-        public ValueTask<bool> IsTransitivelyAvailableAsync(string packageName, CancellationToken token)
-            => TargetFrameworks.ToAsyncEnumerable().AnyAwaitAsync(tfm => ContainsDependencyAsync(tfm, d => string.Equals(packageName, d.Id, StringComparison.OrdinalIgnoreCase), token), cancellationToken: token);
+        public async ValueTask<bool> IsTransitivelyAvailableAsync(string packageName, CancellationToken token)
+            => PackageReferences.Any(p => p.Name.Equals(packageName, StringComparison.OrdinalIgnoreCase))
+            || (PackageReferenceFormat == NugetPackageFormat.PackageReference && await TargetFrameworks.ToAsyncEnumerable().AnyAwaitAsync(tfm => ContainsPackageDependencyAsync(tfm, d => string.Equals(packageName, d.Id, StringComparison.OrdinalIgnoreCase), token), cancellationToken: token).ConfigureAwait(false));
 
-        public ValueTask<bool> IsTransitiveDependencyAsync(NuGetReference nugetReference, CancellationToken token)
-            => TargetFrameworks.ToAsyncEnumerable().AnyAwaitAsync(tfm => ContainsDependencyAsync(tfm, d => ReferenceSatisfiesDependency(d, nugetReference, true), token), token);
+        public async ValueTask<bool> IsTransitiveDependencyAsync(NuGetReference nugetReference, CancellationToken token)
+            => PackageReferenceFormat == NugetPackageFormat.PackageReference && await TargetFrameworks.ToAsyncEnumerable().AnyAwaitAsync(tfm => ContainsPackageDependencyAsync(tfm, d => ReferenceSatisfiesDependency(d, nugetReference, true), token), token).ConfigureAwait(false);
 
         private static bool ReferenceSatisfiesDependency(PackageDependency dependency, NuGetReference packageReference, bool minVersionMatchOnly)
         {
@@ -104,16 +110,21 @@ namespace Microsoft.DotNet.UpgradeAssistant.MSBuild
             return true;
         }
 
-        private ValueTask<bool> ContainsDependencyAsync(TargetFrameworkMoniker tfm, Func<PackageDependency, bool> filter, CancellationToken token)
-            => GetAllDependenciesAsync(tfm, token).AnyAsync(l => l.Dependencies.Any(d => filter(d)), token);
+        private ValueTask<bool> ContainsPackageDependencyAsync(TargetFrameworkMoniker tfm, Func<PackageDependency, bool> filter, CancellationToken token)
+            => GetAllPackageReferenceDependenciesAsync(tfm, token).AnyAsync(l => l.Dependencies.Any(d => filter(d)), token);
 
-        private async IAsyncEnumerable<LockFileTargetLibrary> GetAllDependenciesAsync(TargetFrameworkMoniker tfm, [EnumeratorCancellation] CancellationToken token)
+        private async IAsyncEnumerable<LockFileTargetLibrary> GetAllPackageReferenceDependenciesAsync(TargetFrameworkMoniker tfm, [EnumeratorCancellation] CancellationToken token)
         {
             if (!IsRestored)
             {
                 throw new InvalidOperationException("Project should have already been restored. Please file an issue at https://github.com/dotnet/upgrade-assistant");
             }
 
+            if (PackageReferenceFormat != NugetPackageFormat.PackageReference)
+            {
+                throw new InvalidOperationException("PackageReference restore for transitive dependencies should only happen for PackageReference package reference format");
+            }
+
             var parsedTfm = NuGetFramework.Parse(tfm.Name);
             var target = GetLockFileTarget(parsedTfm);