Add test to verify linked file updating works properly.

src/EditorFeatures/Test2/Diagnostics/AbstractCrossLanguageUserDiagnosticTest.vb

@@ -44,7 +44,7 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.Diagnostics
                             Optional codeActionIndex As Integer = 0,
                             Optional verifyTokens As Boolean = True,
                             Optional fileNameToExpected As Dictionary(Of String, String) = Nothing,
-                            Optional verifySolutions As Action(Of Solution, Solution) = Nothing,
+                            Optional verifySolutions As Func(Of Solution, Solution, Task) = Nothing,
                             Optional onAfterWorkspaceCreated As Action(Of TestWorkspace) = Nothing) As Task
             Using workspace = TestWorkspace.CreateWorkspace(definition)
                 onAfterWorkspaceCreated?.Invoke(workspace)
@@ -65,16 +65,20 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.Diagnostics
 
                 Dim updatedSolution = workspace.CurrentSolution
 
-                verifySolutions?.Invoke(oldSolution, updatedSolution)
+                If verifySolutions IsNot Nothing Then
+                    Await verifySolutions(oldSolution, updatedSolution)
+                End If
 
-                If expected Is Nothing AndAlso fileNameToExpected Is Nothing Then
+                If expected Is Nothing AndAlso
+                   fileNameToExpected Is Nothing AndAlso
+                   verifySolutions Is Nothing Then
                     Dim projectChanges = SolutionUtilities.GetSingleChangedProjectChanges(oldSolution, updatedSolution)
                     Assert.Empty(projectChanges.GetChangedDocuments())
                 ElseIf expected IsNot Nothing Then
                     Dim updatedDocument = SolutionUtilities.GetSingleChangedDocument(oldSolution, updatedSolution)
 
                     Await VerifyAsync(expected, verifyTokens, updatedDocument)
-                Else
+                ElseIf fileNameToExpected IsNot Nothing Then
                     For Each kvp In fileNameToExpected
                         Dim updatedDocument = updatedSolution.Projects.SelectMany(Function(p) p.Documents).Single(Function(d) d.Name = kvp.Key)
                         Await VerifyAsync(kvp.Value, verifyTokens, updatedDocument)
@@ -134,7 +138,7 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.Diagnostics
             Dim hostDocument = GetHostDocument(workspace)
 
             Dim invocationBuffer = hostDocument.TextBuffer
-            Dim invocationPoint = workspace.Documents.Single(Function(d) d.CursorPosition.HasValue).CursorPosition.Value
+            Dim invocationPoint = workspace.Documents.Single(Function(d) d.CursorPosition.HasValue AndAlso Not d.IsLinkFile).CursorPosition.Value
 
             Dim document = workspace.CurrentSolution.GetDocument(hostDocument.Id)
 

src/EditorFeatures/Test2/Diagnostics/AddImport/AddImportCrossLanguageTests.vb

@@ -11,6 +11,7 @@ Imports Microsoft.CodeAnalysis.IncrementalCaches
 Imports Microsoft.CodeAnalysis.SolutionCrawler
 Imports Microsoft.CodeAnalysis.UnitTests
 Imports Microsoft.CodeAnalysis.VisualBasic.AddImport
+Imports Roslyn.Utilities
 
 Namespace Microsoft.CodeAnalysis.Editor.UnitTests.Diagnostics.AddImport
 
@@ -509,12 +510,12 @@ namespace CSAssembly2
                             Optional codeActionIndex As Integer = 0,
                             Optional addedReference As String = Nothing,
                             Optional onAfterWorkspaceCreated As Action(Of TestWorkspace) = Nothing) As Task
-            Dim verifySolutions As Action(Of Solution, Solution) = Nothing
+            Dim verifySolutions As Func(Of Solution, Solution, Task) = Nothing
             Dim workspace As TestWorkspace = Nothing
 
             If addedReference IsNot Nothing Then
                 verifySolutions =
-                    Sub(oldSolution As Solution, newSolution As Solution)
+                    Function(oldSolution As Solution, newSolution As Solution)
                         Dim initialDocId = workspace.DocumentWithCursor.Id
                         Dim oldProject = oldSolution.GetDocument(initialDocId).Project
                         Dim newProject = newSolution.GetDocument(initialDocId).Project
@@ -529,7 +530,8 @@ namespace CSAssembly2
                                                    Select p.Name
 
                         Assert.True(newProjectReferences.Contains(addedReference))
-                    End Sub
+                        Return SpecializedTasks.EmptyTask
+                    End Function
             End If
 
             Await TestAsync(definition, expected, codeActionIndex,

src/EditorFeatures/Test2/Diagnostics/UseAutoProperty/UseAutoPropertyTests.vb

@@ -94,5 +94,54 @@ end class
 </text>.Value.Trim()}
                 })
         End Function
+
+        <Fact(), Trait(Traits.Feature, Traits.Features.CodeActionsUseAutoProperty)>
+        Public Async Function TestLinkedFile() As System.Threading.Tasks.Task
+            Dim input =
+                <Workspace>
+                    <Project Language="C#" CommonReferences="true" AssemblyName="LinkedProj" Name="CSProj.1">
+                        <Document FilePath='C.cs'>
+partial class C
+{
+    $$int i;
+
+    public int P { get { return i; } }
+
+    public C()
+    {
+        this.i = 0;
+    }
+}
+                        </Document>
+                    </Project>
+                    <Project Language="C#" CommonReferences="true" AssemblyName="LinkedProj" Name="CSProj.2">
+                        <Document IsLinkFile="true" LinkProjectName="CSProj.1" LinkFilePath="C.cs"/>
+                    </Project>
+                </Workspace>
+
+            Dim expectedText = "
+partial class C
+{
+
+    public int P { get; private set; }
+
+    public C()
+    {
+        this.P = 0;
+    }
+}".Trim()
+
+            Await TestAsync(input, verifySolutions:=
+                Async Function(oldSolution, newSolution)
+                    Dim documents = newSolution.Projects.SelectMany(Function(p) p.Documents).
+                                                         Where(Function(d) d.Name = "C.cs")
+                    Assert.Equal(2, documents.Count())
+
+                    For Each doc In documents
+                        Dim text = (Await doc.GetTextAsync()).ToString().Trim()
+                        Assert.Equal(expectedText, text)
+                    Next
+                End Function)
+        End Function
     End Class
 End Namespace