Pylance Ports Still Listed After VS Code Close On WSL

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Pylance Ports Still Listed After VS Code Close on WSL

Hey guys! Today, we're diving into a quirky issue that some of you might have encountered while using VS Code with Pylance on a Remote: WSL (Windows Subsystem for Linux) setup. Specifically, we're talking about those pesky forwarded ports that seem to stick around even after you've closed VS Code. It's like that one guest who just doesn't want to leave the party, right? Let's break down what's happening, why it's happening, and how we can tackle it.

The Curious Case of Lingering Pylance Ports

So, here's the scenario: You're working on a Python project within WSL, and Pylance – the super helpful language server for Python in VS Code – kicks in to provide all those neat features like auto-completion, error checking, and more. To do its magic, Pylance spins up an instance on a random port. All good so far. But, the problem arises when you close VS Code. Instead of gracefully shutting down and cleaning up after itself, it seems like the old Pylance forwarded ports remain listed. This is where things start to get a little messy.

Imagine reopening VS Code on another Python file, and boom, you've got another forwarded port listed. Over time, this can lead to a whole bunch of ports cluttering up the landscape, even though only one Pylance process is actively running. It's like having a phantom army of ports, and nobody wants that! This issue appears to stem from the Pylance process not being terminated correctly on the remote WSL environment when VS Code closes. Interestingly, this problem doesn't seem to pop up as frequently on the Windows host itself, making it a bit of a WSL-specific head-scratcher.

Why Does This Happen?

The million-dollar question, right? While we don't have a definitive answer etched in stone, the clues suggest that the issue lies in how the Pylance process is being managed within the Remote: WSL environment. It's possible that the shutdown signals aren't being correctly propagated, or that there's a timing issue where VS Code closes before Pylance has a chance to fully shut down. Whatever the root cause, the result is the same: orphaned ports lingering like forgotten party balloons.

The Impact of Unclosed Ports

Okay, so you've got a few extra ports listed – what's the big deal? Well, while it might seem like a minor annoyance, these lingering ports can actually cause a few headaches down the line. For starters, it's just plain messy. A cluttered port list makes it harder to see what's actually in use, which can be a pain when you're trying to debug networking issues or configure other services. More importantly, each of these unclosed ports represents a potential resource leak. While they might not be consuming a ton of resources individually, a large number of them can start to add up, potentially impacting performance or even leading to port exhaustion issues. Nobody wants their development environment to grind to a halt because of a port traffic jam!

Decoding the Environment Data

To get a clearer picture, let's look at the environment where this issue was observed. The user who reported this was running:

  • Pylance version: 2025.9.1
  • OS: Fedora 42 WSL2 on Microsoft Windows 11 Pro, version 10.0.26100 build 26100
  • Python version: Python 3.13.7

This setup is fairly typical for developers using WSL for Python development, which means that this issue could potentially affect a wide range of users. The fact that it's happening on a relatively recent version of Pylance (2025.9.1) suggests that it's not an ancient bug that's been lurking in the shadows for ages. It's a present-day puzzle that needs solving!

Reproducing the Port Problem: A Step-by-Step Guide

To really understand an issue, it's often helpful to reproduce it yourself. So, if you're curious to see this port-lingering phenomenon in action, here's a step-by-step guide:

  1. Open a Python file on WSL: Fire up VS Code and open any Python file within your WSL environment. This will kickstart Pylance and get the ball rolling.
  2. Wait for the extension to activate and forward a port: Give Pylance a moment to do its thing. You should see a new port being forwarded for the Pylance process.
  3. Close VS Code: Time to shut things down. Close your VS Code window.
  4. Re-open VS Code on WSL: Now, reopen VS Code and connect to your WSL environment again.
  5. Open a Python file: Open another Python file (or the same one) to reactivate Pylance.

If you're experiencing this issue, you should now see multiple ports listed, even though only one Pylance process is actually running. Ta-da! You've reproduced the problem.

Expected vs. Actual Behavior

So, what should happen, and what's actually happening? Ideally, when you close VS Code, the Pylance process should terminate cleanly, and any forwarded ports should be closed along with it. This means that when you reopen VS Code, you should only see one port listed for the current Pylance process. However, the actual behavior is that the old ports remain listed, creating a bit of a port graveyard. It's like the ports are saying,