[feat]: Request for more output in stdout/stderr for non-interactive process

[robinjhuang]

Summary

Hi!

We are using uv to install python venvs and pytorch in our desktop application. I previously posted our issue of not getting interactive output in a regular subprocess #9129.

Would it be possible to include more detailed output? Doesn't have to be interactive. The issue is that right now when we install a requirements.txt file, we don't see any output until everything is finished.

If I launch uv pip instal torch torchvision torchaudio, nothing is written to stdout or stderr until it's finished. Since torch with cuda is large, this can take a while.

[stderr] Resolved 14 packages in 7ms
[stderr] Installed 14 packages in 327ms
[stderr]  + filelock==3.17.0
 + fsspec==2024.12.0
 + jinja2==3.1.5
 + markupsafe==3.0.2
 + mpmath==1.3.0
 + networkx==3.4.2
 + numpy==2.2.2
 + pillow==11.1.0
 + setuptools==75.8.0
 + sympy==1.13.1
 + torch==2.6.0
 + torchaudio==2.6.0
 + torchvision==0.21.0
 + typing-extensions==4.12.2

What would be ideal is:

Resolved 14 packages in 7ms
Installing fsspec...
Finished installing fsspec.
Installing jinja2...

Example

No response

[webfiltered]

Definitely an update of package installed would be good at a minimum. Adding some kind of rudimentary fixed-length percent update, e.g. output 100 full stops for each package, would be a significant improvement in monitoring the uv process' progress without an interactive terminal.

Unless there is some other way for the calling process to see current download updates (even active polling)?

[konstin]

We have an interactive progress bar for downloads, i assume that's not showing for you?

Screencast.from.2025-01-31.11-16-49.webm

Can you share which platform and terminal you're using; Are you applying any redirects of stdout/stderr?

[webfiltered]

Hey, thanks for the quick response! The indicatif progress is great whenever we're observing via terminal on any platform.

The issue we're facing is when stdout/stderr are not connected to a terminal, there is simply no output at all. We're using spawn in node.js, but the same holds true for python subprocess.

[webfiltered]

Apologies, forgot to answer everything. Tested on Windows 11 & Ubuntu 24. If we spawn uv via node-pty, we get output and can log / observe monitor. But this comes with its own limitations and introduces several more issues.

If there is a proper / better way to interpret current state / progress from a calling process, we'd be happy to use that.

[zanieb]

Hm it's weird that we wouldn't write output when using subprocess. I'd consider that a bug, if we can reproduce.

@Gankra is considering allowing interaction with current state from a parent process using a json-lines output, but that's a bit separate.

[robinjhuang]

To be clear, there is some amount of output right now using subprocess (posted above). But we don't get the progress bars of any sort. Using uv 0.5.25. Would be great to get the progress in stdout or stderr as well using subprocess, even if it's not well-formatted.

[zanieb]

Oh.. yeah the progress bars don't work in a non-interactive mode (and I wouldn't expect them to). They require repeated drawing in the terminal.

I don't think we'll implement simple visibility into progress in this context — the json-lines output format is the way to go here.

[webfiltered]

Ah sorry, by nothing, I meant nothing from the point where uv starts downloading until it exits (even if it's 20 packages).

[robinjhuang]

JSON output would be great! What sort of output would it look like?

{ name: "pyyaml", progress: "0.25" , state: "downloading" }

Something like that?

[zanieb]

Still TBD, @Gankra would have more details but we're still designing this. See also #411

[robinjhuang]

@webfiltered Did some digging and we realized we might be able to use RUST_LOG=trace to get way more output in subprocess. Using string parsing, this seems like a good enough solution to track progress of installations.

Leaving this here for anyone else who might benefit.