Better support for reading ProjectReference items in MSBuildWorkspace.

When MSBuildWorkspace is reading .csproj/.vbproj files, it now doesn't crash if the <Project> metadata item (GUID) on a <ProjectReference> item is not set (there are some project references out there that don't specify a GUID). Since VS allows such project references, we should too.

Also, if <ReferenceOutputAssembly> is set to false, we will now just skip the reference. Earlier we were ignoring this metadata and always adding a reference. (changeset 1211532)

Src/Workspaces/CSharp/MSBuild/CSharpProjectFileLoader.CSharpProjectFile.cs

@@ -66,9 +66,11 @@ protected override IEnumerable<ProjectFileReference> GetProjectReferences(Projec
 
             private IEnumerable<ProjectFileReference> GetProjectReferencesCore(ProjectInstance executedProject)
             {
-                foreach (var projectReference in executedProject.GetItems("ProjectReference"))
+                foreach (var projectReference in GetProjectReferenceItems(executedProject))
                 {
-                    var guid = Guid.Parse(projectReference.GetMetadataValue("Project"));
+                    Guid guid;
+                    Guid.TryParse(projectReference.GetMetadataValue("Project"), out guid);
+
                     var filePath = projectReference.EvaluatedInclude;
 
                     string[] aliases;

Src/Workspaces/Core/Workspace/MSBuild/ProjectFile/ProjectFile.cs

@@ -217,9 +217,25 @@ protected virtual string GetAssemblyName()
 
         protected virtual IEnumerable<ProjectFileReference> GetProjectReferences(MSB.Execution.ProjectInstance executedProject)
         {
-            return executedProject.GetItems("ProjectReference")
-                        .Select(reference => new ProjectFileReference(Guid.Parse(reference.GetMetadataValue("Project")), reference.EvaluatedInclude))
-                        .ToImmutableList();
+            var builder = ImmutableList.CreateBuilder<ProjectFileReference>();
+            foreach (var referenceItem in GetProjectReferenceItems(executedProject))
+            {
+                Guid guid;
+                Guid.TryParse(referenceItem.GetMetadataValue("Project"), out guid);
+                builder.Add(new ProjectFileReference(guid, referenceItem.EvaluatedInclude));
+            }
+
+            return builder.ToImmutable();
+        }
+
+        protected IEnumerable<ProjectItemInstance> GetProjectReferenceItems(ProjectInstance executedProject)
+        {
+            return executedProject
+                .GetItems("ProjectReference")
+                .Where(i => !string.Equals(
+                    i.GetMetadataValue("ReferenceOutputAssembly"),
+                    bool.FalseString,
+                    StringComparison.OrdinalIgnoreCase));
         }
 
         protected virtual IEnumerable<MSB.Framework.ITaskItem> GetDocumentsFromModel(MSB.Execution.ProjectInstance executedProject)

Src/Workspaces/Test/MSBuildWorkspaceTests.cs

@@ -5,6 +5,7 @@
 using System.IO;
 using System.Linq;
 using System.Threading;
+using System.Xml.Linq;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Host;
@@ -22,6 +23,8 @@ namespace Microsoft.CodeAnalysis.UnitTests
 {
     public partial class MSBuildWorkspaceTests : TestBase
     {
+        private const string MSBuildNamespace = "http://schemas.microsoft.com/developer/msbuild/2003";
+
         [Fact, Trait(Traits.Feature, Traits.Features.Workspace)]
         public void TestCreateWorkspace()
         {
@@ -1540,6 +1543,79 @@ public void TestProjectReferenceWithExternAlias()
             }
         }
 
+        [Fact, Trait(Traits.Feature, Traits.Features.Workspace)]
+        public void TestProjectReferenceWithReferenceOutputAssemblyFalse()
+        {
+            var files = GetProjectReferenceSolutionFiles();
+            files = VisitProjectReferences(files, r =>
+            {
+                r.Add(new XElement(XName.Get("ReferenceOutputAssembly", MSBuildNamespace), "false"));
+            });
+
+            CreateFiles(files);
+
+            var fullPath = Path.Combine(this.solutionDirectory.Path, @"CSharpProjectReference.sln");
+            using (var ws = MSBuildWorkspace.Create())
+            {
+                var sol = ws.OpenSolutionAsync(fullPath).Result;
+                foreach (var project in sol.Projects)
+                {
+                    Assert.Equal(0, project.ProjectReferences.Count());
+                }
+            }
+        }
+
+        private FileSet VisitProjectReferences(FileSet files, Action<XElement> visitProjectReference)
+        {
+            var result = new List<KeyValuePair<string, object>>();
+            foreach (var file in files)
+            {
+                string text = file.Value.ToString();
+                if (file.Key.EndsWith("proj", StringComparison.OrdinalIgnoreCase))
+                {
+                    text = VisitProjectReferences(text, visitProjectReference);
+                }
+
+                result.Add(new KeyValuePair<string, object>(file.Key, text));
+            }
+
+            return new FileSet(result);
+        }
+
+        private string VisitProjectReferences(string projectFileText, Action<XElement> visitProjectReference)
+        {
+            var document = XDocument.Parse(projectFileText);
+            var projectReferenceItems = document.Descendants(XName.Get("ProjectReference", MSBuildNamespace));
+            foreach (var projectReferenceItem in projectReferenceItems)
+            {
+                visitProjectReference(projectReferenceItem);
+            }
+
+            return document.ToString();
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.Workspace)]
+        public void TestProjectReferenceWithNoGuid()
+        {
+            var files = GetProjectReferenceSolutionFiles();
+            files = VisitProjectReferences(files, r =>
+            {
+                r.Elements(XName.Get("Project", MSBuildNamespace)).Remove();
+            });
+
+            CreateFiles(files);
+
+            var fullPath = Path.Combine(this.solutionDirectory.Path, @"CSharpProjectReference.sln");
+            using (var ws = MSBuildWorkspace.Create())
+            {
+                var sol = ws.OpenSolutionAsync(fullPath).Result;
+                foreach (var project in sol.Projects)
+                {
+                    Assert.InRange(project.ProjectReferences.Count(), 0, 1);
+                }
+            }
+        }
+
         [Fact, Trait(Traits.Feature, Traits.Features.Workspace)]
         public void TestLoadedProjectHasMetadataDocComments()
         {