From 6752867c1fb2aaac27080e64f9120fc492ed832a Mon Sep 17 00:00:00 2001
From: CyrusNajmabadi <cyrusn@microsoft.com>
Date: Thu, 20 Apr 2017 12:28:12 -0700
Subject: [PATCH] Acquire the user's selection up-front if we're on the UI
 thread for light-bulbs.

There are circumstances where the editor will call into us on hte UI thread and will then
block for results.  Right now this can deadlock as we may have kicked off work to the BG
that then awaits getting the selection back from the UI thread.  To avoid that, if we're on
the UI thread when we start, just go and get the selection and pass it along.
---
 .../Suggestions/SuggestedActionsSource.cs     | 54 ++++++++++---------
 1 file changed, 28 insertions(+), 26 deletions(-)

diff --git a/src/EditorFeatures/Core/Implementation/Suggestions/SuggestedActionsSource.cs b/src/EditorFeatures/Core/Implementation/Suggestions/SuggestedActionsSource.cs
index 9f5f5345229..c035aa0b1cd 100644
--- a/src/EditorFeatures/Core/Implementation/Suggestions/SuggestedActionsSource.cs
+++ b/src/EditorFeatures/Core/Implementation/Suggestions/SuggestedActionsSource.cs
@@ -604,6 +604,25 @@ public async Task<bool> HasSuggestedActionsAsync(ISuggestedActionCategorySet req
 
                 using (var asyncToken = provider.OperationListener.BeginAsyncOperation("HasSuggestedActionsAsync"))
                 {
+                    // Acquire the user's selection up front, before we do any async work, so that we can
+                    // directly grab it when we're on the UI thread.  That way we don't have any reentrancy
+                    // blocking concerns if VS wants to block on this call (for example, if the user 
+                    // explicitly invokes the 'show smart tag' command).
+                    TextSpan? selection = null;
+                    if (IsForeground())
+                    {
+                        // This operation needs to happen on UI thread because it needs to access textView.Selection.
+                        selection = TryGetCodeRefactoringSelection(buffer, view, range);
+                    }
+                    else
+                    {
+                        await InvokeBelowInputPriority(() =>
+                        {
+                            // This operation needs to happen on UI thread because it needs to access textView.Selection.
+                            selection = TryGetCodeRefactoringSelection(buffer, view, range);
+                        }).ConfigureAwait(false);
+                    }
+
                     var document = await GetMatchingDocumentAsync(range.Snapshot, cancellationToken).ConfigureAwait(false);
                     if (document == null)
                     {
@@ -614,7 +633,7 @@ public async Task<bool> HasSuggestedActionsAsync(ISuggestedActionCategorySet req
 
                     return
                         await HasFixesAsync(provider, document, range, cancellationToken).ConfigureAwait(false) ||
-                        await HasRefactoringsAsync(provider, document, buffer, view, range, cancellationToken).ConfigureAwait(false);
+                        await HasRefactoringsAsync(provider, document, selection, cancellationToken).ConfigureAwait(false);
                 }
             }
 
@@ -655,11 +674,16 @@ public async Task<bool> HasSuggestedActionsAsync(ISuggestedActionCategorySet req
             private async Task<bool> HasRefactoringsAsync(
                 SuggestedActionsSourceProvider provider,
                 Document document,
-                ITextBuffer buffer,
-                ITextView view,
-                SnapshotSpan range,
+                TextSpan? selection,
                 CancellationToken cancellationToken)
             {
+                if (!selection.HasValue)
+                {
+                    // this is here to fail test and see why it is failed.
+                    Trace.WriteLine("given range is not current");
+                    return false;
+                }
+
                 var workspace = document.Project.Solution.Workspace;
                 var supportsFeatureService = workspace.Services.GetService<IDocumentSupportsFeatureService>();
 
@@ -667,28 +691,6 @@ public async Task<bool> HasSuggestedActionsAsync(ISuggestedActionCategorySet req
                     provider._codeRefactoringService != null &&
                     supportsFeatureService.SupportsRefactorings(document))
                 {
-                    TextSpan? selection = null;
-                    if (IsForeground())
-                    {
-                        // This operation needs to happen on UI thread because it needs to access textView.Selection.
-                        selection = TryGetCodeRefactoringSelection(buffer, view, range);
-                    }
-                    else
-                    {
-                        await InvokeBelowInputPriority(() =>
-                        {
-                                // This operation needs to happen on UI thread because it needs to access textView.Selection.
-                                selection = TryGetCodeRefactoringSelection(buffer, view, range);
-                        }).ConfigureAwait(false);
-                    }
-
-                    if (!selection.HasValue)
-                    {
-                        // this is here to fail test and see why it is failed.
-                        Trace.WriteLine("given range is not current");
-                        return false;
-                    }
-
                     return await Task.Run(
                         () => provider._codeRefactoringService.HasRefactoringsAsync(
                             document, selection.Value, cancellationToken),
-- 
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