Merge pull request #4791 from mattwar/Bug3931

Fix check for missing/unsupported language

src/Workspaces/Core/Desktop/PublicAPI.Unshipped.txt

@@ -8,3 +8,4 @@ Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.MSBuildProjectLoader(Microso
 Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.Properties.get -> System.Collections.Immutable.ImmutableDictionary<string, string>
 Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.SkipUnrecognizedProjects.get -> bool
 Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.SkipUnrecognizedProjects.set -> void
+static Microsoft.CodeAnalysis.MSBuild.MSBuildWorkspace.Create(Microsoft.CodeAnalysis.Host.HostServices hostServices) -> Microsoft.CodeAnalysis.MSBuild.MSBuildWorkspace
\ No newline at end of file

src/Workspaces/Core/Desktop/Workspace/MSBuild/MSBuildProjectLoader.cs

@@ -716,6 +716,21 @@ private bool TryGetLoaderFromProjectPath(string projectFilePath, ReportMode mode
                     }
                 }
 
+                // since we have both C# and VB loaders in this same library, it no longer indicates whether we have full language support available.
+                if (loader != null)
+                {
+                    language = loader.Language;
+
+                    // check for command line parser existing... if not then error.
+                    var commandLineParser = _workspace.Services.GetLanguageServices(language).GetService<ICommandLineParserService>();
+                    if (commandLineParser == null)
+                    {
+                        loader = null;
+                        this.ReportFailure(mode, string.Format(WorkspacesResources.CannotOpenProjectUnsupportedLanguage, projectFilePath, language));
+                        return false;
+                    }
+                }
+
                 return loader != null;
             }
         }

src/Workspaces/Core/Desktop/Workspace/MSBuild/MSBuildWorkspace.cs

@@ -60,6 +60,15 @@ public static MSBuildWorkspace Create(IDictionary<string, string> properties)
             return Create(properties, DesktopMefHostServices.DefaultServices);
         }
 
+        /// <summary>
+        /// Create a new instance of a workspace that can be populated by opening solution and project files.
+        /// </summary>
+        /// <param name="hostServices">The <see cref="HostServices"/> used to configure this workspace.</param>
+        public static MSBuildWorkspace Create(HostServices hostServices)
+        {
+            return Create(ImmutableDictionary<string, string>.Empty, hostServices);
+        }
+
         /// <summary>
         /// Create a new instance of a workspace that can be populated by opening solution and project files.
         /// </summary>

src/Workspaces/CoreTest/WorkspaceTests/MSBuildWorkspaceTests.cs

@@ -11,6 +11,8 @@
 using System.Xml.Linq;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.MSBuild;
 using Microsoft.CodeAnalysis.Test.Utilities;
 using Microsoft.CodeAnalysis.Text;
@@ -1031,6 +1033,67 @@ public void TestOpenSolution_WithUnrecognizedProjectTypeGuidAndUnrecognizedExten
             });
         }
 
+        private HostServices hostServicesWithoutCSharp = MefHostServices.Create(MefHostServices.DefaultAssemblies.Where(a => !a.FullName.Contains("CSharp")));
+
+        [Fact, Trait(Traits.Feature, Traits.Features.Workspace)]
+        [WorkItem(3931, "https://github.com/dotnet/roslyn/issues/3931")]
+        public void TestOpenSolution_WithMissingLanguageLibraries_WithSkipFalse_Throws()
+        {
+            // proves that if the language libaries are missing then the appropriate error occurs
+            CreateFiles(GetSimpleCSharpSolutionFiles());
+
+            AssertThrows<InvalidOperationException>(() =>
+            {
+                var ws = MSBuildWorkspace.Create(hostServicesWithoutCSharp);
+                ws.SkipUnrecognizedProjects = false;
+                var solution = ws.OpenSolutionAsync(GetSolutionFileName(@"TestSolution.sln")).Result;
+            },
+            e =>
+            {
+                Assert.Equal(true, e.Message.Contains("extension"));
+            });
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.Workspace)]
+        [WorkItem(3931, "https://github.com/dotnet/roslyn/issues/3931")]
+        public void TestOpenSolution_WithMissingLanguageLibraries_WithSkipTrue_SucceedsWithDiagnostic()
+        {
+            // proves that if the language libaries are missing then the appropriate error occurs
+            CreateFiles(GetSimpleCSharpSolutionFiles());
+
+            var ws = MSBuildWorkspace.Create(hostServicesWithoutCSharp);
+            ws.SkipUnrecognizedProjects = true;
+
+            var dx = new List<WorkspaceDiagnostic>();
+            ws.WorkspaceFailed += delegate (object sender, WorkspaceDiagnosticEventArgs e)
+            {
+                dx.Add(e.Diagnostic);
+            };
+
+            var solution = ws.OpenSolutionAsync(GetSolutionFileName(@"TestSolution.sln")).Result;
+
+            Assert.Equal(1, dx.Count);
+            Assert.True(dx[0].Message.Contains("extension"));
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.Workspace)]
+        [WorkItem(3931, "https://github.com/dotnet/roslyn/issues/3931")]
+        public void TestOpenProject_WithMissingLanguageLibraries_Throws()
+        {
+            // proves that if the language libaries are missing then the appropriate error occurs
+            CreateFiles(GetSimpleCSharpSolutionFiles());
+
+            AssertThrows<InvalidOperationException>(() =>
+            {
+                var ws = MSBuildWorkspace.Create(hostServicesWithoutCSharp);
+                var project = ws.OpenProjectAsync(GetSolutionFileName(@"CSharpProject\CSharpProject.csproj")).Result;
+            },
+            e =>
+            {
+                Assert.Equal(true, e.Message.Contains("extension"));
+            });
+        }
+
         [Fact, Trait(Traits.Feature, Traits.Features.Workspace)]
         public void TestOpenProject_WithInvalidFilePath_Fails()
         {