[Fixes #4555] Assemblies with a transitive dependency to MVC are not included as part of the list of discovered assemblies

src/Microsoft.AspNetCore.Mvc.Core/Internal/DefaultAssemblyPartDiscoveryProvider.cs

@@ -63,14 +63,96 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 return Enumerable.Empty<RuntimeLibrary>();
             }
 
-            return dependencyContext.RuntimeLibraries.Where(IsCandidateLibrary);
+            var candidatesResolver = new CandidateResolver(dependencyContext.RuntimeLibraries, ReferenceAssemblies);
+            return candidatesResolver.GetCandidates();
         }
 
-        private static bool IsCandidateLibrary(RuntimeLibrary library)
+        private class CandidateResolver
         {
-            Debug.Assert(ReferenceAssemblies != null);
+            private readonly IDictionary<string, Dependency> _dependencies;
-            return !ReferenceAssemblies.Contains(library.Name) &&
+
-                library.Dependencies.Any(dependency => ReferenceAssemblies.Contains(dependency.Name));
+            public CandidateResolver(IReadOnlyList<RuntimeLibrary> dependencies, ISet<string> referenceAssemblies)
+            {
+                _dependencies = dependencies
+                    .ToDictionary(d => d.Name, d => CreateDependency(d, referenceAssemblies));
+            }
+
+            private Dependency CreateDependency(RuntimeLibrary library, ISet<string> referenceAssemblies)
+            {
+                var classification = DependencyClassification.Unknown;
+                if (referenceAssemblies.Contains(library.Name))
+                {
+                    classification = DependencyClassification.MvcReference;
+                }
+
+                return new Dependency(library, classification);
+            }
+
+            private DependencyClassification ComputeClassification(string dependency)
+            {
+                Debug.Assert(_dependencies.ContainsKey(dependency));
+
+                var candidateEntry = _dependencies[dependency];
+                if (candidateEntry.Classification != DependencyClassification.Unknown)
+                {
+                    return candidateEntry.Classification;
+                }
+                else
+                {
+                    var classification = DependencyClassification.NotCandidate;
+                    foreach (var candidateDependency in candidateEntry.Library.Dependencies)
+                    {
+                        var dependencyClassification = ComputeClassification(candidateDependency.Name);
+                        if (dependencyClassification == DependencyClassification.Candidate ||
+                            dependencyClassification == DependencyClassification.MvcReference)
+                        {
+                            classification = DependencyClassification.Candidate;
+                            break;
+                        }
+                    }
+
+                    candidateEntry.Classification = classification;
+
+                    return classification;
+                }
+            }
+
+            public IEnumerable<RuntimeLibrary> GetCandidates()
+            {
+                foreach (var dependency in _dependencies)
+                {
+                    if (ComputeClassification(dependency.Key) == DependencyClassification.Candidate)
+                    {
+                        yield return dependency.Value.Library;
+                    }
+                }
+            }
+
+            private class Dependency
+            {
+                public Dependency(RuntimeLibrary library, DependencyClassification classification)
+                {
+                    Library = library;
+                    Classification = classification;
+                }
+
+                public RuntimeLibrary Library { get; }
+
+                public DependencyClassification Classification { get; set; }
+
+                public override string ToString()
+                {
+                    return $"Library: {Library.Name}, Classification: {Classification}";
+                }
+            }
+
+            private enum DependencyClassification
+            {
+                Unknown = 0,
+                Candidate = 1,
+                NotCandidate = 2,
+                MvcReference = 3
+            }
         }
     }
 }

test/Microsoft.AspNetCore.Mvc.Core.Test/Internal/DefaultAssemblyPartDiscoveryProviderTest.cs

@@ -63,6 +63,12 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                      GetLibrary("Bar", "Microsoft.AspNetCore.Mvc"),
                      GetLibrary("Qux", "Not.Mvc.Assembly", "Unofficial.Microsoft.AspNetCore.Mvc"),
                      GetLibrary("Baz", "Microsoft.AspNetCore.Mvc.Abstractions"),
+                     GetLibrary("Microsoft.AspNetCore.Mvc.Core"),
+                     GetLibrary("Microsoft.AspNetCore.Mvc"),
+                     GetLibrary("Not.Mvc.Assembly"),
+                     GetLibrary("Unofficial.Microsoft.AspNetCore.Mvc"),
+                     GetLibrary("Microsoft.AspNetCore.Mvc.Abstractions"),
+
                 },
                 Enumerable.Empty<RuntimeFallbacks>());
 
@@ -73,6 +79,45 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             Assert.Equal(new[] { "Foo", "Bar", "Baz" }, candidates.Select(a => a.Name));
         }
 
+        [Fact]
+        public void GetCandidateLibraries_ReturnsLibrariesWithTransitiveReferencesToAnyMvcAssembly()
+        {
+            // Arrange
+            var expectedLibraries = new[] { "Foo", "Bar", "Baz", "LibraryA", "LibraryB", "LibraryC", "LibraryE", "LibraryG", "LibraryH" };
+
+            var dependencyContext = new DependencyContext(
+                new TargetInfo("framework", "runtime", "signature", isPortable: true),
+                CompilationOptions.Default,
+                new CompilationLibrary[0],
+                new[]
+                {
+                     GetLibrary("Foo", "Bar"),
+                     GetLibrary("Bar", "Microsoft.AspNetCore.Mvc"),
+                     GetLibrary("Qux", "Not.Mvc.Assembly", "Unofficial.Microsoft.AspNetCore.Mvc"),
+                     GetLibrary("Baz", "Microsoft.AspNetCore.Mvc.Abstractions"),
+                     GetLibrary("Microsoft.AspNetCore.Mvc"),
+                     GetLibrary("Not.Mvc.Assembly"),
+                     GetLibrary("Microsoft.AspNetCore.Mvc.Abstractions"),
+                     GetLibrary("Unofficial.Microsoft.AspNetCore.Mvc"),
+                     GetLibrary("LibraryA", "LibraryB"),
+                     GetLibrary("LibraryB","LibraryC"),
+                     GetLibrary("LibraryC", "LibraryD", "Microsoft.AspNetCore.Mvc.Abstractions"),
+                     GetLibrary("LibraryD"),
+                     GetLibrary("LibraryE","LibraryF","LibraryG"),
+                     GetLibrary("LibraryF"),
+                     GetLibrary("LibraryG", "LibraryH"),
+                     GetLibrary("LibraryH", "LibraryI", "Microsoft.AspNetCore.Mvc"),
+                     GetLibrary("LibraryI")
+                },
+                Enumerable.Empty<RuntimeFallbacks>());
+
+            // Act
+            var candidates = DefaultAssemblyPartDiscoveryProvider.GetCandidateLibraries(dependencyContext);
+
+            // Assert
+            Assert.Equal(expectedLibraries, candidates.Select(a => a.Name));
+        }
+
         [Fact]
         public void GetCandidateLibraries_SkipsMvcAssemblies()
         {
@@ -84,11 +129,13 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 new[]
                 {
                      GetLibrary("MvcSandbox", "Microsoft.AspNetCore.Mvc.Core", "Microsoft.AspNetCore.Mvc"),
-                     GetLibrary("Microsoft.AspNetCore.Mvc.TagHelpers", "Microsoft.AspNetCore.Mvc.Razor"),
-                     GetLibrary("Microsoft.AspNetCore.Mvc", "Microsoft.AspNetCore.Mvc.Abstractions", "Microsoft.AspNetCore.Mvc.Core"),
                      GetLibrary("Microsoft.AspNetCore.Mvc.Core", "Microsoft.AspNetCore.HttpAbstractions"),
+                     GetLibrary("Microsoft.AspNetCore.HttpAbstractions"),
+                     GetLibrary("Microsoft.AspNetCore.Mvc", "Microsoft.AspNetCore.Mvc.Abstractions", "Microsoft.AspNetCore.Mvc.Core"),
+                     GetLibrary("Microsoft.AspNetCore.Mvc.Abstractions"),
+                     GetLibrary("Microsoft.AspNetCore.Mvc.TagHelpers", "Microsoft.AspNetCore.Mvc.Razor"),
+                     GetLibrary("Microsoft.AspNetCore.Mvc.Razor"),
                      GetLibrary("ControllersAssembly", "Microsoft.AspNetCore.Mvc"),
-
                 },
                 Enumerable.Empty<RuntimeFallbacks>());