Merge pull request #39554 from allisonchou/MultiCaretBug

Fix for split string literals broken with multi-carets

src/EditorFeatures/CSharp/SplitStringLiteral/SplitStringLiteralCommandHandler.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 using System.ComponentModel.Composition;
+using System.Linq;
 using System.Threading;
-using Microsoft.CodeAnalysis.Editor;
 using Microsoft.CodeAnalysis.Editor.Shared.Extensions;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
 using Microsoft.CodeAnalysis.Formatting;
@@ -56,22 +56,43 @@ public bool ExecuteCommandWorker(ReturnKeyCommandArgs args)
             var spans = textView.Selection.GetSnapshotSpansOnBuffer(subjectBuffer);
 
             // Don't split strings if there is any actual selection.
-            if (spans.Count == 1 && spans[0].IsEmpty)
+            // We must check all spans to account for multi-carets.
+            if (spans.IsEmpty() || !spans.All(s => s.IsEmpty))
             {
-                var caret = textView.GetCaretPoint(subjectBuffer);
-                if (caret != null)
+                return false;
+            }
+
+            var caret = textView.GetCaretPoint(subjectBuffer);
+            if (caret == null)
+            {
+                return false;
+            }
+
+            // First, we need to verify that we are only working with string literals.
+            // Otherwise, let the editor handle all carets.
+            foreach (var span in spans)
+            {
+                var spanStart = span.Start;
+                var line = subjectBuffer.CurrentSnapshot.GetLineFromPosition(span.Start);
+                if (!LineContainsQuote(line, span.Start))
                 {
-                    // Quick check.  If the line doesn't contain a quote in it before the caret,
-                    // then no point in doing any more expensive synchronous work.
-                    var line = subjectBuffer.CurrentSnapshot.GetLineFromPosition(caret.Value);
-                    if (LineContainsQuote(line, caret.Value))
-                    {
-                        return SplitString(textView, subjectBuffer, caret.Value);
-                    }
+                    return false;
                 }
             }
 
-            return false;
+            // We now go through the verified string literals and split each of them.
+            // The list of spans is traversed in reverse order so we do not have to
+            // deal with updating later caret positions to account for the added space
+            // from splitting at earlier caret positions.
+            foreach (var span in spans.Reverse())
+            {
+                if (!SplitString(textView, subjectBuffer, span.Start))
+                {
+                    return false;
+                }
+            }
+
+            return true;
         }
 
         private bool SplitString(ITextView textView, ITextBuffer subjectBuffer, SnapshotPoint caret)

src/EditorFeatures/CSharpTest/SplitStringLiteral/SplitStringLiteralCommandHandlerTests.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
 using Microsoft.CodeAnalysis.Editor.CSharp.SplitStringLiteral;
@@ -10,6 +11,7 @@
 using Microsoft.CodeAnalysis.Test.Utilities;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.CodeAnalysis.Text.Shared.Extensions;
+using Microsoft.VisualStudio.Text;
 using Microsoft.VisualStudio.Text.Editor.Commanding.Commands;
 using Microsoft.VisualStudio.Text.Operations;
 using Roslyn.Test.Utilities;
@@ -41,8 +43,14 @@ public class SplitStringLiteralCommandHandlerTests
             var view = document.GetTextView();
 
             var originalSnapshot = view.TextBuffer.CurrentSnapshot;
-            var originalSelection = document.SelectedSpans.Single();
-            view.SetSelection(originalSelection.ToSnapshotSpan(originalSnapshot));
+            var originalSelections = document.SelectedSpans;
+
+            var snapshotSpans = new List<SnapshotSpan>();
+            foreach (var selection in originalSelections)
+            {
+                snapshotSpans.Add(selection.ToSnapshotSpan(originalSnapshot));
+            }
+            view.SetMultiSelection(snapshotSpans);
 
             var undoHistoryRegistry = workspace.GetService<ITextUndoHistoryRegistry>();
             var commandHandler = new SplitStringLiteralCommandHandler(
@@ -60,17 +68,17 @@ public class SplitStringLiteralCommandHandlerTests
                     out var expectedOutput, out ImmutableArray<TextSpan> expectedSpans);
 
                 Assert.Equal(expectedOutput, view.TextBuffer.CurrentSnapshot.AsText().ToString());
-                Assert.Equal(expectedSpans.Single().Start, view.Caret.Position.BufferPosition.Position);
+                Assert.Equal(expectedSpans.First().Start, view.Caret.Position.BufferPosition.Position);
 
                 if (verifyUndo)
                 {
                     // Ensure that after undo we go back to where we were to begin with.
                     var history = undoHistoryRegistry.GetHistory(document.GetTextBuffer());
-                    history.Undo(count: 1);
+                    history.Undo(count: originalSelections.Count);
 
                     var currentSnapshot = document.GetTextBuffer().CurrentSnapshot;
                     Assert.Equal(originalSnapshot.GetText(), currentSnapshot.GetText());
-                    Assert.Equal(originalSelection.Start, view.Caret.Position.BufferPosition.Position);
+                    Assert.Equal(originalSelections.First().Start, view.Caret.Position.BufferPosition.Position);
                 }
             }
         }
@@ -744,5 +752,85 @@ static void Main(string[] args)
 }",
             verifyUndo: false);
         }
+
+        [WorkItem(39040, "https://github.com/dotnet/roslyn/issues/39040")]
+        [WpfFact, Trait(Traits.Feature, Traits.Features.SplitStringLiteral)]
+        public void TestMultiCaretSingleLine()
+        {
+            TestHandled(
+@"class C
+{
+    void M()
+    {
+        var v = ""now is [||]the ti[||]me"";
+    }
+}",
+@"class C
+{
+    void M()
+    {
+        var v = ""now is "" +
+            ""[||]the ti"" +
+            ""[||]me"";
+    }
+}");
+        }
+
+        [WorkItem(39040, "https://github.com/dotnet/roslyn/issues/39040")]
+        [WpfFact, Trait(Traits.Feature, Traits.Features.SplitStringLiteral)]
+        public void TestMultiCaretMultiLines()
+        {
+            TestHandled(
+@"class C
+{
+    string s = ""hello w[||]orld"";
+
+    void M()
+    {
+        var v = ""now is [||]the ti[||]me"";
+    }
+}",
+@"class C
+{
+    string s = ""hello w"" +
+        ""[||]orld"";
+
+    void M()
+    {
+        var v = ""now is "" +
+            ""[||]the ti"" +
+            ""[||]me"";
+    }
+}");
+        }
+
+        [WorkItem(39040, "https://github.com/dotnet/roslyn/issues/39040")]
+        [WpfFact, Trait(Traits.Feature, Traits.Features.SplitStringLiteral)]
+        public void TestMultiCaretInterpolatedString()
+        {
+            TestHandled(
+@"class C
+{
+    string s = ""hello w[||]orld"";
+
+    void M()
+    {
+        var location = ""world"";
+        var s = $""H[||]ello {location}!"";
+    }
+}",
+@"class C
+{
+    string s = ""hello w"" +
+        ""[||]orld"";
+
+    void M()
+    {
+        var location = ""world"";
+        var s = $""H"" +
+            $""[||]ello {location}!"";
+    }
+}");
+        }
     }
 }