Updates to py_require()

[t-kalinowski]

Changes:

• Update order of discovery:

  • continue to discover r-reticualte venv before bootstrapping
  • only bootstrap a venv if initializing python
  • give a way to opt out

• Update uv_get_or_create_env():

  • pass through stderr from uv
  • simplify pre+post processing

• Update uv_binary()

  • allow resolving without bootstraping install

• Update uv cache resolution:

  • Fix issue where reticulate resolved the incorrect cache dir if a user-managed uv installation is used. Right now this is done by forcing to always use the reticulate cache, but it might make sense instead to let uv use it's default uv cache dir if the uv installation is not managed by reticulate.

• Changes to tests:

  • declare requirements for tests with py_require()
  • capture stderr from uv in tests
  • use color in snapshots
  • skip tests around cache resolution that fail if using user-installed uv
  • skip tests of py_require() that fail if python is already initialized

[t-kalinowski]

Restarting R session...

> reticulate::repl_python()
Python 3.13.1 (/Users/tomasz/Library/Caches/r-reticulate/uv-cache/archive-v0/Kc-xLPZ1uy6xA8d7Kourf/bin/python3)
Reticulate 1.40.0.9000 REPL -- A Python interpreter in R.
Enter 'exit' or 'quit' to exit the REPL and return to R.
>>> 

• We might want to change how we present the path to the python installation here, seeing the actual path in the cache dir isn't helpful. Maybe something like:

  Python 3.13.1 (Reticulate managed installation)
  Installed Python Packages: numpy, pandas, ...<other requirements from py_require()>
  Reticulate 1.40.0.9000 REPL -- A Python interpreter in R.
  Enter 'exit' or 'quit' to exit the REPL and return to R.

• We should probably default to Python 3.11 here, given this is a fresh R session.

[edgararuiz]

We should probably default to Python 3.11 here, given this is a fresh R session.

You're talking about only for repl_python(), right?

[edgararuiz]

We might want to change how we present the path to the python installation here, seeing the actual path in the cache dir isn't helpful.

I would suggest to go even simpler:

Python version: 3.13.1 
Installed Python packages: numpy, pandas, ...<other requirements from py_require()>
Reticulate 1.40.0.9000 REPL -- A Python interpreter in R.
Enter 'exit' or 'quit' to exit the REPL and return to R.

[t-kalinowski]

You're talking about only for repl_python(), right?

Good question. Maybe we should modify the print methods for py_config and py_last_error too, to avoid showing the path to the cached env.

[edgararuiz]

Actually, using UV_PYTHON seems to be a good mechanism to set a "soft" default:

> x <- uv_get_or_create_env()
> system2(x, c("--version"))     
Python 3.13.1
> 
> withr::with_envvar(
+   list("UV_PYTHON" = "3.11"), {
+     x <- uv_get_or_create_env()
+     system2(x, c("--version"))
+   }
+ )
Python 3.11.11                   
> 
> withr::with_envvar(
+   list("UV_PYTHON" = "3.11"), {
+     x <- uv_get_or_create_env(python_version = c("3.10"))  
+     system2(x, c("--version"))
+   }
+ )
Python 3.10.16                   
> 
> withr::with_envvar(
+   list("UV_PYTHON" = "3.11"), {
+     x <- uv_get_or_create_env(python_version = c(">=3.11", "<=3.12"))  
+     system2(x, c("--version"))
+   }
+ )
Python 3.12.0  

[t-kalinowski]

Thanks Edgar! I merged to unblock Max; We'll address remaining issues in followup PR's.