Address CodeQL findings on E2E tests and harness

- Bind awaited results in async helpers to silence `no-effect''
  warnings (Python `await x` -> `_ = await x`).
- Add explanatory comments to intentional `except ExceptionGroup: pass`
  blocks in test_rpc_server_e2e.py.
- HookLifecycleAndOutputE2ETests: remove unused errorInputs container.
- ClientOptionsE2ETests: dispose TcpListener via `using`.
- RpcShellAndFleetE2ETests: simplify `Contains(...) == true` to a
  null-coalescing form.
- SessionConfigE2ETests/SessionE2ETests: use `catch (Exception)` in
  `DisposeAsync` cleanup blocks instead of bare `catch`.
- E2ETestContext.ResolveSymlinks: replace libc realpath/free P/Invoke
  with managed `DirectoryInfo.ResolveLinkTarget`-based component walk;
  preserves macOS `/var -> /private/var` resolution behavior. Also
  switches the fallback `catch` to typed exceptions.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: stephentoub

dotnet/test/E2E/ClientOptionsE2ETests.cs

@@ -244,7 +244,7 @@ public void Should_Accept_SessionIdleTimeoutSeconds_Option()
 
     private static int GetAvailableTcpPort()
     {
-        var listener = new TcpListener(IPAddress.Loopback, 0);
+        using var listener = new TcpListener(IPAddress.Loopback, 0);
         listener.Start();
         try
         {

dotnet/test/E2E/HookLifecycleAndOutputE2ETests.cs

@@ -109,15 +109,13 @@ public async Task Should_Invoke_OnSessionEnd_Hook_When_Session_Is_Disconnected()
     [Fact]
     public async Task Should_Invoke_OnErrorOccurred_Hook_When_Error_Occurs()
     {
-        var errorInputs = new List<ErrorOccurredHookInput>();
         CopilotSession? session = null;
         session = await CreateSessionAsync(new SessionConfig
         {
             Hooks = new SessionHooks
             {
                 OnErrorOccurred = (input, invocation) =>
                 {
-                    errorInputs.Add(input);
                     Assert.Equal(session!.SessionId, invocation.SessionId);
                     Assert.True(input.Timestamp > 0);
                     Assert.False(string.IsNullOrEmpty(input.Cwd));

dotnet/test/E2E/RpcShellAndFleetE2ETests.cs

@@ -71,7 +71,7 @@ public async Task Should_Start_Fleet_And_Complete_Custom_Tool_Task()
         Assert.Contains(
             messages.OfType<ToolExecutionCompleteEvent>(),
             message => message.Data.Success &&
-                message.Data.Result?.Content.Contains(marker, StringComparison.Ordinal) == true);
+                (message.Data.Result?.Content?.Contains(marker, StringComparison.Ordinal) ?? false));
         Assert.Contains(
             messages.OfType<AssistantMessageEvent>(),
             message => (message.Data.Content ?? string.Empty).Contains("fleet task", StringComparison.OrdinalIgnoreCase));

dotnet/test/E2E/SessionConfigE2ETests.cs

@@ -289,7 +289,7 @@ public async Task Should_Create_Session_With_Custom_Provider_Config()
         {
             await session.DisposeAsync();
         }
-        catch
+        catch (Exception)
         {
             // disconnect may fail since the provider is fake
         }

dotnet/test/E2E/SessionE2ETests.cs

@@ -858,7 +858,7 @@ public async Task Should_Create_Session_With_Custom_Provider()
         {
             await session.DisposeAsync();
         }
-        catch
+        catch (Exception)
         {
             // disconnect may fail since the provider is fake
         }
@@ -887,7 +887,7 @@ public async Task Should_Create_Session_With_Azure_Provider()
         {
             await session.DisposeAsync();
         }
-        catch
+        catch (Exception)
         {
             // disconnect may fail since the provider is fake
         }
@@ -915,7 +915,7 @@ public async Task Should_Resume_Session_With_Custom_Provider()
         {
             await session2.DisposeAsync();
         }
-        catch
+        catch (Exception)
         {
             // disconnect may fail since the provider is fake
         }

dotnet/test/Harness/E2ETestContext.cs

@@ -3,7 +3,6 @@
  *--------------------------------------------------------------------------------------------*/
 
 using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
 using System.Text.RegularExpressions;
 using Microsoft.Extensions.Logging;
 
@@ -51,42 +50,68 @@ public static async Task<E2ETestContext> CreateAsync()
         return new E2ETestContext(homeDir, workDir, proxyUrl, proxy, repoRoot);
     }
 
+    /// <summary>
+    /// Returns a canonical path with symlinks resolved in every directory
+    /// component. .NET has no built-in equivalent of POSIX <c>realpath</c>
+    /// that walks all parents, so we walk the components ourselves and use
+    /// <see cref="DirectoryInfo.ResolveLinkTarget(bool)"/> on each one.
+    /// On Windows, where the test temp paths don't traverse symlinks,
+    /// <see cref="Path.GetFullPath(string)"/> is sufficient.
+    /// </summary>
     private static string ResolveSymlinks(string path)
     {
         if (OperatingSystem.IsWindows())
         {
             return Path.GetFullPath(path);
         }
 
-        IntPtr resolved = IntPtr.Zero;
         try
         {
-            resolved = NativeRealpath(path, IntPtr.Zero);
-            if (resolved == IntPtr.Zero)
+            var fullPath = Path.GetFullPath(path);
+            var root = Path.GetPathRoot(fullPath);
+            if (string.IsNullOrEmpty(root))
             {
-                return Path.GetFullPath(path);
+                return fullPath;
             }
-            return Marshal.PtrToStringAnsi(resolved) ?? Path.GetFullPath(path);
+
+            var components = fullPath
+                .Substring(root.Length)
+                .Split(Path.DirectorySeparatorChar, StringSplitOptions.RemoveEmptyEntries);
+
+            var resolved = root;
+            foreach (var component in components)
+            {
+                resolved = Path.Combine(resolved, component);
+                try
+                {
+                    var info = new DirectoryInfo(resolved);
+                    if (info.Exists && info.LinkTarget != null)
+                    {
+                        var target = info.ResolveLinkTarget(returnFinalTarget: true);
+                        if (target != null && !string.IsNullOrEmpty(target.FullName))
+                        {
+                            resolved = target.FullName;
+                        }
+                    }
+                }
+                catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
+                {
+                    // Component we can't inspect; keep what we have and continue.
+                }
+            }
+
+            return resolved;
         }
-        catch
+        catch (Exception ex) when (ex is IOException
+            or UnauthorizedAccessException
+            or ArgumentException
+            or NotSupportedException
+            or PathTooLongException)
         {
             return Path.GetFullPath(path);
         }
-        finally
-        {
-            if (resolved != IntPtr.Zero)
-            {
-                NativeFree(resolved);
-            }
-        }
     }
 
-    [DllImport("libc", EntryPoint = "realpath", CharSet = CharSet.Ansi, BestFitMapping = false, ThrowOnUnmappableChar = true)]
-    private static extern IntPtr NativeRealpath([MarshalAs(UnmanagedType.LPStr)] string path, IntPtr resolved);
-
-    [DllImport("libc", EntryPoint = "free")]
-    private static extern void NativeFree(IntPtr ptr);
-
     private static string FindRepoRoot()
     {
         var dir = new DirectoryInfo(AppContext.BaseDirectory);

python/e2e/test_pending_work_resume_e2e.py

@@ -159,7 +159,7 @@ def original_tool_handler(args):
                 await session1.send(
                     "Use resume_permission_tool with value 'alpha', then reply with the result."
                 )
-                await captured_request
+                _captured_permission_request = await captured_request
                 permission_event = await permission_event_task
 
                 # Force-stop the suspended client without releasing the in-flight

python/e2e/test_rpc_mcp_and_skills_e2e.py

@@ -61,7 +61,7 @@ def _assert_skill(skills, skill_name: str, *, enabled: bool):
 
 async def _assert_failure(awaitable, expected: str) -> None:
     with pytest.raises(Exception) as excinfo:
-        await awaitable
+        _result = await awaitable
     assert expected.lower() in str(excinfo.value).lower()
 
 

python/e2e/test_rpc_server_e2e.py

@@ -104,6 +104,9 @@ async def test_should_call_rpc_models_list_with_typed_result(self, authed_ctx: E
             try:
                 await client.stop()
             except ExceptionGroup:
+                # Intentional: shutting down the per-test client can race the
+                # CLI's own teardown and surface as an aggregated cancellation
+                # error from anyio. We don't want it to fail the test.
                 pass
 
     async def test_should_call_rpc_account_get_quota_when_authenticated(
@@ -140,6 +143,9 @@ async def test_should_call_rpc_account_get_quota_when_authenticated(
             try:
                 await client.stop()
             except ExceptionGroup:
+                # Intentional: shutting down the per-test client can race the
+                # CLI's own teardown and surface as an aggregated cancellation
+                # error from anyio. We don't want it to fail the test.
                 pass
 
     async def test_should_call_rpc_tools_list_with_typed_result(self, ctx: E2ETestContext):

python/e2e/test_rpc_session_state_e2e.py

@@ -43,7 +43,7 @@ def _conversation_messages(events) -> list[tuple[str, str]]:
 
 async def _assert_implemented_failure(awaitable, method: str) -> None:
     with pytest.raises(Exception) as excinfo:
-        await awaitable
+        _result = await awaitable
     assert f"Unhandled method {method}".lower() not in str(excinfo.value).lower()