Do not throw if a library does not have a runtime component

Fixes #5690

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

@@ -3,7 +3,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
 using Microsoft.AspNetCore.Mvc.ApplicationParts;
@@ -71,12 +70,12 @@ namespace Microsoft.AspNetCore.Mvc.Internal
 
         private class CandidateResolver
         {
-            private readonly IDictionary<string, Dependency> _dependencies;
+            private readonly IDictionary<string, Dependency> _runtimeDependencies;
 
-            public CandidateResolver(IReadOnlyList<RuntimeLibrary> dependencies, ISet<string> referenceAssemblies)
+            public CandidateResolver(IReadOnlyList<RuntimeLibrary> runtimeDependencies, ISet<string> referenceAssemblies)
             {
                 var dependenciesWithNoDuplicates = new Dictionary<string, Dependency>(StringComparer.OrdinalIgnoreCase);
-                foreach (var dependency in dependencies)
+                foreach (var dependency in runtimeDependencies)
                 {
                     if (dependenciesWithNoDuplicates.ContainsKey(dependency.Name))
                     {
@@ -85,7 +84,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                     dependenciesWithNoDuplicates.Add(dependency.Name, CreateDependency(dependency, referenceAssemblies));
                 }
 
-                _dependencies = dependenciesWithNoDuplicates;
+                _runtimeDependencies = dependenciesWithNoDuplicates;
             }
 
             private Dependency CreateDependency(RuntimeLibrary library, ISet<string> referenceAssemblies)
@@ -101,23 +100,28 @@ namespace Microsoft.AspNetCore.Mvc.Internal
 
             private DependencyClassification ComputeClassification(string dependency)
             {
-                Debug.Assert(_dependencies.ContainsKey(dependency));
+                if (!_runtimeDependencies.ContainsKey(dependency))
+                {
+                    // Library does not have runtime dependency. Since we can't infer
+                    // anything about it's references, we'll assume it does not have a reference to Mvc.
+                    return DependencyClassification.DoesNotReferenceMvc;
+                }
 
-                var candidateEntry = _dependencies[dependency];
+                var candidateEntry = _runtimeDependencies[dependency];
                 if (candidateEntry.Classification != DependencyClassification.Unknown)
                 {
                     return candidateEntry.Classification;
                 }
                 else
                 {
-                    var classification = DependencyClassification.NotCandidate;
+                    var classification = DependencyClassification.DoesNotReferenceMvc;
                     foreach (var candidateDependency in candidateEntry.Library.Dependencies)
                     {
                         var dependencyClassification = ComputeClassification(candidateDependency.Name);
-                        if (dependencyClassification == DependencyClassification.Candidate ||
+                        if (dependencyClassification == DependencyClassification.ReferencesMvc ||
                             dependencyClassification == DependencyClassification.MvcReference)
                         {
-                            classification = DependencyClassification.Candidate;
+                            classification = DependencyClassification.ReferencesMvc;
                             break;
                         }
                     }
@@ -130,9 +134,9 @@ namespace Microsoft.AspNetCore.Mvc.Internal
 
             public IEnumerable<RuntimeLibrary> GetCandidates()
             {
-                foreach (var dependency in _dependencies)
+                foreach (var dependency in _runtimeDependencies)
                 {
-                    if (ComputeClassification(dependency.Key) == DependencyClassification.Candidate)
+                    if (ComputeClassification(dependency.Key) == DependencyClassification.ReferencesMvc)
                     {
                         yield return dependency.Value.Library;
                     }
@@ -160,9 +164,23 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             private enum DependencyClassification
             {
                 Unknown = 0,
-                Candidate = 1,
+
-                NotCandidate = 2,
+                /// <summary>
-                MvcReference = 3
+                /// References (directly or transitively) one of the Mvc packages listed in
+                /// <see cref="ReferenceAssemblies"/>.
+                /// </summary>
+                ReferencesMvc = 1,
+
+                /// <summary>
+                /// Does not reference (directly or transitively) one of the Mvc packages listed by
+                /// <see cref="ReferenceAssemblies"/>.
+                /// </summary>
+                DoesNotReferenceMvc = 2,
+
+                /// <summary>
+                /// One of the references listed in <see cref="ReferenceAssemblies"/>.
+                /// </summary>
+                MvcReference = 3,
             }
         }
     }

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

@@ -64,6 +64,30 @@ namespace Microsoft.AspNetCore.Mvc.Internal
             Assert.Equal(new[] { expected }, candidates);
         }
 
+        [Fact]
+        public void GetCandidateLibraries_DoesNotThrow_IfLibraryDoesNotHaveRuntimeComponent()
+        {
+            // Arrange
+            var expected = GetLibrary("MyApplication", "Microsoft.AspNetCore.Server.Kestrel", "Microsoft.AspNetCore.Mvc");
+            var deps = new DependencyContext(
+                new TargetInfo("netcoreapp1.1", "rurntime", "signature", isPortable: true),
+                CompilationOptions.Default,
+                Enumerable.Empty<CompilationLibrary>(),
+                new[]
+                {
+                    expected,
+                    GetLibrary("Microsoft.AspNetCore.Server.Kestrel", "Libuv"),
+                    GetLibrary("Microsoft.AspNetCore.Mvc"),
+                },
+                Enumerable.Empty<RuntimeFallbacks>());
+
+            // Act
+            var candidates = DefaultAssemblyPartDiscoveryProvider.GetCandidateLibraries(deps).ToList();
+
+            // Assert
+            Assert.Equal(new[] { expected }, candidates);
+        }
+
         [Fact]
         public void CandidateAssemblies_ReturnsEntryAssemblyIfDependencyContextIsNull()
         {