Ensure source paths leave 40 characters for root (dotnet#11835)

The default path for VS is in the user directory, which ends up being something like `C:\Users\jkuhne\source\repos\winforms`.

Recent paths make the repo impossible to sync. I've added a test that reserves 40 characters for the repro root path and moved files out of subdirectories that violated that.

A longer follow up is to see if we can pick some type names that aren't so long. Additionally we should try to up this check to 50 characters- which would require more renaming.

src/System.Windows.Forms.Analyzers.CSharp/tests/UnitTests/System/Windows/Forms/Generators/ApplicationConfigurationGeneratorTests.cs → src/System.Windows.Forms.Analyzers.CSharp/tests/UnitTests/Generators/ApplicationConfigurationGeneratorTests.cs

@@ -220,6 +220,6 @@ public async Task CS_ApplicationConfigurationGenerator_GenerateInitialize_user_s
 
     private SourceText LoadFileContent(string testName) =>
         SourceText.From(
-            File.ReadAllText($@"System\Windows\Forms\Generators\MockData\{GetType().Name}.{testName}.cs"),
+            File.ReadAllText($@"Generators\MockData\{GetType().Name}.{testName}.cs"),
             Encoding.UTF8);
 }

src/System.Windows.Forms.Analyzers.CSharp/tests/UnitTests/System/Windows/Forms/Generators/ApplicationConfigurationInitializeBuilderTests.cs → src/System.Windows.Forms.Analyzers.CSharp/tests/UnitTests/Generators/ApplicationConfigurationInitializeBuilderTests.cs

@@ -30,7 +30,7 @@ public partial class ApplicationConfigurationInitializeBuilderTests
     [InlineData("MyProject", "default_boilerplate")]
     public void ApplicationConfigurationInitializeBuilder_GenerateInitialize_can_handle_namespace(string? ns, string expectedFileName)
     {
-        string expected = File.ReadAllText($@"System\Windows\Forms\Generators\MockData\{GetType().Name}.{expectedFileName}.cs");
+        string expected = File.ReadAllText($@"Generators\MockData\{GetType().Name}.{expectedFileName}.cs");
 
         string output = ApplicationConfigurationInitializeBuilder.GenerateInitialize(ns,
             new ApplicationConfig(

src/System.Windows.Forms.Analyzers.CSharp/tests/UnitTests/System.Windows.Forms.Analyzers.CSharp.Tests.csproj

@@ -28,8 +28,8 @@
   </ItemGroup>
 
   <ItemGroup>
-    <Compile Remove="System\Windows\Forms\Generators\MockData\*.cs" />
-    <None Include="System\Windows\Forms\Generators\MockData\*.*">
+    <Compile Remove="Generators\MockData\*.cs" />
+    <None Include="Generators\MockData\*.*">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
   </ItemGroup>

src/System.Windows.Forms.Analyzers.VisualBasic/tests/UnitTests/System.Windows.Forms.Analyzers.VisualBasic.Tests/System.Windows.Forms.Analyzers.VisualBasic.Tests.vbproj

@@ -28,10 +28,4 @@
     <ProjectReference Include="..\..\..\src\System.Windows.Forms.Analyzers.VisualBasic.vbproj" />
   </ItemGroup>
 
-  <ItemGroup>
-    <None Include="System\Windows\Forms\Generators\MockData\*.*">
-      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-    </None>
-  </ItemGroup>
-
 </Project>

src/System.Windows.Forms.Primitives/tests/TestUtilities.Tests/PathLengthTests.cs

@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using FluentAssertions;
+using System.IO.Enumeration;
+
+namespace System.Tests;
+
+public class PathLengthTests
+{
+    [Fact]
+    public void RepoPathsLeaveRoomForRoot()
+    {
+        string currentPath = typeof(PathLengthTests).Assembly.Location;
+        currentPath = Path.GetFullPath(@"..\..\..\..\..\..\src", currentPath);
+        Directory.Exists(currentPath).Should().BeTrue();
+
+        // Current path will be something like C:\Users\jkuhne\source\repos\winforms\src (41 chars, 38 without src).
+        // We want to reserve 40 characters of the path length for everything past src.
+        int currentRootLength = currentPath.Length - "src".Length;
+
+        const int MaxRootLength = 40;
+
+        int maxLength = 260 - (currentRootLength > MaxRootLength
+            ? MaxRootLength
+            : MaxRootLength + (MaxRootLength - currentRootLength));
+
+        FileSystemEnumerable<string> enumerable = new(
+            currentPath,
+            (ref FileSystemEntry entry) => entry.ToFullPath(),
+            new EnumerationOptions() {  RecurseSubdirectories = true })
+            {
+                ShouldIncludePredicate = (ref FileSystemEntry entry) =>
+                    // Directory doesn't contain a trailing slash
+                    entry.Directory.Length + entry.FileName.Length > maxLength
+            };
+
+        enumerable.Should().BeEmpty();
+    }
+}