fix(cli): limit test parallelism on Windows to avoid pipe error (#22776)

One last attempt to fix the parallelism issue on Windows.

cli/lsp/testing/execution.rs

@@ -245,6 +245,13 @@ impl TestRun {
       unreachable!("Should always be Test subcommand.");
     };
 
+    // TODO(mmastrac): Temporarily limit concurrency in windows testing to avoid named pipe issue:
+    // *** Unexpected server pipe failure '"\\\\.\\pipe\\deno_pipe_e30f45c9df61b1e4.1198.222\\0"': 3
+    // This is likely because we're hitting some sort of invisible resource limit
+    // This limit is both in cli/lsp/testing/execution.rs and cli/tools/test/mod.rs
+    #[cfg(windows)]
+    let concurrent_jobs = std::cmp::min(concurrent_jobs, 4);
+
     let (test_event_sender_factory, mut receiver) = create_test_event_channel();
     let fail_fast_tracker = FailFastTracker::new(fail_fast);
 

cli/tools/test/mod.rs

@@ -1191,8 +1191,18 @@ async fn test_specifiers(
     })
   });
 
+  // TODO(mmastrac): Temporarily limit concurrency in windows testing to avoid named pipe issue:
+  // *** Unexpected server pipe failure '"\\\\.\\pipe\\deno_pipe_e30f45c9df61b1e4.1198.222\\0"': 3
+  // This is likely because we're hitting some sort of invisible resource limit
+  // This limit is both in cli/lsp/testing/execution.rs and cli/tools/test/mod.rs
+  let concurrent = if cfg!(windows) {
+    std::cmp::min(concurrent_jobs.get(), 4)
+  } else {
+    concurrent_jobs.get()
+  };
+
   let join_stream = stream::iter(join_handles)
-    .buffer_unordered(concurrent_jobs.get())
+    .buffer_unordered(concurrent)
     .collect::<Vec<Result<Result<(), AnyError>, tokio::task::JoinError>>>();
 
   let handler = spawn(async move { report_tests(receiver, reporter).await.0 });