Removing recursion in SyntaxNode.FindTriviaByOffset

(with test)

Adding VB test for this change and original fix #5528

src/Compilers/CSharp/Test/Syntax/Syntax/SyntaxNodeTests.cs

@@ -8,6 +8,7 @@
 using Roslyn.Test.Utilities;
 using Xunit;
 using InternalSyntax = Microsoft.CodeAnalysis.CSharp.Syntax.InternalSyntax;
+using System.Text;
 
 namespace Microsoft.CodeAnalysis.CSharp.UnitTests
 {
@@ -2936,5 +2937,30 @@ public void TestTriviaExists()
             Assert.Equal(1, nodeOrToken.GetTrailingTrivia().Count);
             Assert.Equal(2, nodeOrToken.GetTrailingTrivia().Span.Length); // zero-width elastic trivia
         }
+
+
+        [WorkItem(6536, "https://github.com/dotnet/roslyn/issues/6536")]
+        [Fact]
+        public void TestFindTrivia_NoStackOverflowOnLargeExpression()
+        {
+            StringBuilder code = new StringBuilder();
+            code.Append(
+@"class Foo
+{
+    void Bar()
+    {
+        string test = ");
+            for (var i = 0; i < 3000; i++)
+            {
+                code.Append(@"""asdf"" + ");
+            }
+            code.Append(@"""last"";
+    }
+}");
+            var tree = SyntaxFactory.ParseSyntaxTree(code.ToString());
+            var position = 4000;
+            var trivia = tree.GetCompilationUnitRoot().FindTrivia(position);
+            // no stack overflow
+        }
     }
 }

src/Compilers/Core/Portable/Syntax/SyntaxNode.cs

@@ -923,6 +923,7 @@ public SyntaxTrivia FindTrivia(int position, Func<SyntaxTrivia, bool> stepInto)
 
         internal static SyntaxTrivia FindTriviaByOffset(SyntaxNode node, int textOffset, Func<SyntaxTrivia, bool> stepInto = null)
         {
+recurse:
             if (textOffset >= 0)
             {
                 foreach (var element in node.ChildNodesAndTokens())
@@ -932,7 +933,8 @@ internal static SyntaxTrivia FindTriviaByOffset(SyntaxNode node, int textOffset,
                     {
                         if (element.IsNode)
                         {
-                            return FindTriviaByOffset(element.AsNode(), textOffset, stepInto);
+                            node = element.AsNode();
+                            goto recurse;
                         }
                         else if (element.IsToken)
                         {
@@ -946,7 +948,8 @@ internal static SyntaxTrivia FindTriviaByOffset(SyntaxNode node, int textOffset,
                                     {
                                         if (trivia.HasStructure && stepInto != null && stepInto(trivia))
                                         {
-                                            return FindTriviaByOffset(trivia.GetStructure(), textOffset, stepInto);
+                                            node = trivia.GetStructure();
+                                            goto recurse;
                                         }
 
                                         return trivia;
@@ -964,7 +967,8 @@ internal static SyntaxTrivia FindTriviaByOffset(SyntaxNode node, int textOffset,
                                     {
                                         if (trivia.HasStructure && stepInto != null && stepInto(trivia))
                                         {
-                                            return FindTriviaByOffset(trivia.GetStructure(), textOffset, stepInto);
+                                            node = trivia.GetStructure();
+                                            goto recurse;
                                         }
 
                                         return trivia;

src/Compilers/VisualBasic/Test/Syntax/TestSyntaxNodes.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 Imports System.Globalization
+Imports System.Text
 Imports Microsoft.CodeAnalysis
 Imports Microsoft.CodeAnalysis.Text
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
@@ -3141,6 +3142,27 @@ End Module
             Assert.Equal(1, x.Count)
         End Sub
 
+
+        <WorkItem(6536, "https://github.com/dotnet/roslyn/issues/6536")>
+        <Fact>
+        Public Sub TestFindTrivia_NoStackOverflowOnLargeExpression()
+            Dim code As New StringBuilder()
+            code.Append(<![CDATA[
+Module Module1
+     Sub Test()
+         Dim c =  ]]>.Value)
+            For i = 0 To 3000
+                code.Append("""asdf"" + ")
+            Next
+            code.AppendLine(<![CDATA["last"
+    End Sub
+End Module]]>.Value)
+
+            Dim tree = VisualBasicSyntaxTree.ParseText(code.ToString())
+            Dim trivia = tree.GetRoot().FindTrivia(4000)
+            ' no stack overflow
+        End Sub
+
 #Region "Equality Verifications"
         <Fact>
         Public Sub Test_GlobalImportsEqual()

src/Workspaces/VisualBasicTest/VisualBasicExtensionsTests.vb

+' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+Imports System.Text
+Imports Microsoft.CodeAnalysis.Text
+Imports Roslyn.Test.Utilities
+Imports Xunit
+Imports Microsoft.CodeAnalysis.VisualBasic.Extensions.SyntaxTreeExtensions
+Imports System.Threading
+
+Namespace Microsoft.CodeAnalysis.VisualBasic.UnitTests
+
+    Public Class VisualBasicExtensionsTests
+        <WorkItem(6536, "https://github.com/dotnet/roslyn/issues/6536")>
+        <Fact>
+        Public Sub TestFindTrivia_NoStackOverflowOnLargeExpression()
+            Dim code As New StringBuilder()
+            code.Append(<![CDATA[
+
+Module Module1
+     Sub Test()
+         Dim c =  ]]>.Value)
+            For i = 0 To 3000
+                code.Append("""asdf"" + ")
+            Next
+            code.AppendLine(<![CDATA["last"
+    End Sub
+End Module]]>.Value)
+
+            Dim tree = VisualBasicSyntaxTree.ParseText(code.ToString())
+            Dim trivia = tree.FindTriviaToLeft(4000, CancellationToken.None)
+            ' no stack overflow
+        End Sub
+
+
+    End Class
+
+End Namespace
\ No newline at end of file

src/Workspaces/VisualBasicTest/VisualBasicServicesTest.vbproj

@@ -92,6 +92,7 @@
       <DesignTime>True</DesignTime>
     </Compile>
     <Compile Include="VisualBasicCommandLineArgumentsFactoryServiceTests.vb" />
+    <Compile Include="VisualBasicExtensionsTests.vb" />
     <Compile Include="VisualBasicSyntaxFactsServiceTests.vb" />
   </ItemGroup>
   <ItemGroup>