Merge pull request #16189 from diryboy/eofSpan2

Fix block comments editing when caret on EOF

src/EditorFeatures/CSharp/BlockCommentEditing/BlockCommentEditingCommandHandler.cs

@@ -160,7 +160,8 @@ private static string GetPaddingOrIndentation(ITextSnapshotLine currentLine, int
 
         private static bool IsCaretInsideBlockCommentSyntax(SnapshotPoint caretPosition)
         {
-            var document = caretPosition.Snapshot.GetOpenDocumentInCurrentContextWithChanges();
+            var snapshot = caretPosition.Snapshot;
+            var document = snapshot.GetOpenDocumentInCurrentContextWithChanges();
             if (document == null)
             {
                 return false;
@@ -170,7 +171,41 @@ private static bool IsCaretInsideBlockCommentSyntax(SnapshotPoint caretPosition)
             var trivia = syntaxTree.FindTriviaAndAdjustForEndOfFile(caretPosition, CancellationToken.None);
 
             var isBlockComment = trivia.IsKind(SyntaxKind.MultiLineCommentTrivia) || trivia.IsKind(SyntaxKind.MultiLineDocumentationCommentTrivia);
-            return isBlockComment && trivia.FullSpan.Start < caretPosition;
+            if (isBlockComment)
+            {
+                var span = trivia.FullSpan;
+                if (span.Start < caretPosition && caretPosition < span.End)
+                {
+                    return true;
+                }
+
+                // FindTriviaAndAdjustForEndOfFile always returns something if position is EOF,
+                // whether or not the result includes the position.
+                // And the SyntaxTrivia for block comments always ends on EOF, closed or not.
+                // So we need to handle
+                // /**/|EOF
+                // and
+                // /*  |EOF
+                if (caretPosition == snapshot.Length)
+                {
+                    if (span.Length < "/**/".Length)
+                    {
+                        return true;
+                    }
+
+                    // If the block comment is not closed, SyntaxTrivia contains diagnostics
+                    // So when the SyntaxTrivia is clean, the block comment should be closed
+                    if (!trivia.ContainsDiagnostics)
+                    {
+                        return false;
+                    }
+
+                    var textBeforeCaret = snapshot.GetText(caretPosition.Position - 2, 2);
+                    return textBeforeCaret != "*/";
+                }
+            }
+
+            return false;
         }
     }
-}
\ No newline at end of file
+}

src/EditorFeatures/CSharpTest/BlockCommentEditing/BlockCommentEditingTests.cs

@@ -69,6 +69,42 @@ public async Task EdgeCase3()
             await VerifyAsync(code, expected);
         }
 
+        [WorkItem(16128, "https://github.com/dotnet/roslyn/issues/16128")]
+        [WpfFact, Trait(Traits.Feature, Traits.Features.BlockCommentEditing)]
+        public async Task EofCase0()
+        {
+            var code = @"
+/* */$$";
+            var expected = @"
+/* */
+$$";
+            await VerifyAsync(code, expected);
+        }
+
+        [WorkItem(16128, "https://github.com/dotnet/roslyn/issues/16128")]
+        [WpfFact, Trait(Traits.Feature, Traits.Features.BlockCommentEditing)]
+        public async Task EofCase1()
+        {
+            var code = @"
+    /*$$";
+            var expected = @"
+    /*
+     * $$";
+            await VerifyAsync(code, expected);
+        }
+
+        [WorkItem(16128, "https://github.com/dotnet/roslyn/issues/16128")]
+        [WpfFact, Trait(Traits.Feature, Traits.Features.BlockCommentEditing)]
+        public async Task EofCase2()
+        {
+            var code = @"
+    /***$$";
+            var expected = @"
+    /***
+     * $$";
+            await VerifyAsync(code, expected);
+        }
+
         [WpfFact, Trait(Traits.Feature, Traits.Features.BlockCommentEditing)]
         public async Task InsertOnStartLine0()
         {