[lldb-dap] Addressing the order of events during disconnect to ensure we shutdown the debugger output handle and error handle redirection before disconnect completes.

The TestDAP_ouput test is flaky due to the order of events during shutdown.  We were stopping the output and error handle redirection after we finished the disconnect request, which can cause us to miss output events due to timing. Moving when we stop the redirection to ensure we have consistent output prior to disconnect responding.

Author: ashgti

lldb/test/API/tools/lldb-dap/output/TestDAP_output.py

@@ -16,6 +16,7 @@ def test_output(self):
         program = self.getBuildArtifact("a.out")
         self.build_and_launch(
             program,
+            disconnectAutomatically=False,
             exitCommands=[
                 # Ensure that output produced by lldb itself is not consumed by the OutputRedirector.
                 "?script print('out\\0\\0', end='\\r\\n', file=sys.stdout)",
@@ -33,6 +34,9 @@ def test_output(self):
 
         self.continue_to_exit()
 
+        # Disconnecting from the server to ensure any pending IO is flushed.
+        self.dap_server.request_disconnect()
+
         output += self.get_stdout(timeout=lldbdap_testcase.DAPTestCaseBase.timeoutval)
         self.assertTrue(output and len(output) > 0, "expect program stdout")
         self.assertIn(

lldb/tools/lldb-dap/DAP.cpp

@@ -223,10 +223,7 @@ llvm::Error DAP::ConfigureIO(std::FILE *overrideOut, std::FILE *overrideErr) {
   return llvm::Error::success();
 }
 
-void DAP::StopIO() {
-  out.Stop();
-  err.Stop();
-
+void DAP::StopEventHandlers() {
   if (event_thread.joinable()) {
     broadcaster.BroadcastEventByType(eBroadcastBitStopEventThread);
     event_thread.join();
@@ -853,13 +850,17 @@ lldb::SBError DAP::Disconnect(bool terminateDebuggee) {
 
   SendTerminatedEvent();
 
+  // Stop forward the debugger output and error file handle.
+  out.Stop();
+  err.Stop();
+
   disconnecting = true;
 
   return error;
 }
 
 llvm::Error DAP::Loop() {
-  auto stop_io = llvm::make_scope_exit([this]() { StopIO(); });
+  auto stop_io = llvm::make_scope_exit([this]() { StopEventHandlers(); });
   while (!disconnecting) {
     llvm::json::Object object;
     lldb_dap::PacketStatus status = GetNextObject(object);

lldb/tools/lldb-dap/DAP.h

@@ -224,8 +224,8 @@ struct DAP {
   llvm::Error ConfigureIO(std::FILE *overrideOut = nullptr,
                           std::FILE *overrideErr = nullptr);
 
-  /// Stop the redirected IO threads and associated pipes.
-  void StopIO();
+  /// Stop event handler threads.
+  void StopEventHandlers();
 
   // Serialize the JSON value into a string and send the JSON packet to
   // the "out" stream.