Allow "request": "attach" and "autoReload": to auto-reload code in remote service

[DiamondJoseph]

I would like to use debugpy to diagnose issues and try potential solutions in a running service. autoReload appears to be mutually exclusive with "request": "attach", only allowed if "request": "launch".

Is this a hard limitation that will never be possible?

Some of the services to be debugged are serving control systems for hardware on specific Kubernetes nodes, so using something like Telepresence to proxy traffic to a local instance of the service is not practical.

Ideally, launching with "request": "attach" and autoReload would connect to the service, allow live code changes and on disconnect return the code to its initial state. Any code changes are preserved on the developer machine and can be re-deployed, leaving the running service in an unknown state for the minimum amount of time.

Snapshot of Intellisense telling me that autoReload is not allowed.

[rchiodo]

Reload is tricky, you can read more about it here (debugpy basically does the same thing as xreload):
https://github.com/JayfonLin/xreload

What you're asking for is reload on attach, which I'm not sure why it isn't supported. Seems like it could be. Essentially there's a thread in the debugger that's just sitting there waiting for file change notifications. It then attempts to reload the affected module. Not sure why that wouldn't work during attach.

The putting everything back on detach would be iffy though. Reload doesn't always work. What if you made a change and it couldn't be put back?

[rchiodo]

Transferring to a discussion item

[DiamondJoseph]

The putting everything back on detach would be iffy though.

If that's not feasible that's fine, just means we [my org] have to enforce that workflow.

If you believe it does/could/should work and can make a minimal example, it could just be that the schema for VSCode's debugpy launch config is incorrect and our [my org's] containerised service build will need to be amended- I've tried making some exploratory changes without success but if I knew it was possible I could dedicate more time.

[rchiodo]

The schema may just be out of date. The launch.json is still sent to the debugger regardless of what errors are from the schema.

Yeah it seems it works for me just fine with attach. I tried it with this launch.json:

    {
      "name": "Python Debugger: Attach to listening debugpy",
      "type": "debugpy",
      "request": "attach",
      "connect": {
        "port": 5691
      },
      "justMyCode": true,
      "logToFile": true,
      "autoReload": {
        "enable": true,
        "include": [
          "**/*.py",
          "**/*.pyw"
        ]
      },

Then I had an app like so:

import debugpy
debugpy.log_to("C:\\Users\\rchiodo\\source\\testing\\test_pylance")
debugpy.listen(5691)  # listen for incoming DAP client connections
debugpy.wait_for_client()  # wait for a client to connect
import os
print(os.getpid())
import test_import_debugattach

print("After attach")

while True:
    input('Hit enter to continue')
    test_import_debugattach.print_something()

And test_import_debugattach.py had this:

def print_something():
    print("Hello, world!")
    return 42

Modifying the print_something after one iteration of the loop yielded this result:

33624
After attach
Hit enter to continue
Hello, world!
Hit enter to continue
Hello, world! after reload
Hit enter to continue

[rchiodo]

Reload is kind of a hack though. Change things too much it and it won't work

[rchiodo]

I entered a PR to change the schema so it would allow autoReload.
microsoft/vscode-python-debugger#676

[DiamondJoseph]

Yep I've observed it working locally now too. I'll investigate further next week.