How to get a create an environment that doesn't install with the default environment?

[matthewfeickert]

While Issue #1067 and PR #1092 are addressing this with the addition of no-default-feature, currently, with pixi 0.18.0, how would you install an environment where there is a directly conflicting dependency with the default environment?

$ pixi --version
pixi 0.18.0

with pixi.toml of

[project]
name = "columnar-analysis-benchmarks"
version = "0.1.0"
description = "Add a short description here"
authors = ["Matthew Feickert <[email protected]>"]
channels = ["conda-forge"]
platforms = ["linux-64"]

[tasks]

[dependencies]
python = "3.11.*"
coffea = "==2024.4.0"

[feature.ab-stable.dependencies]
python = "3.11.*"
coffea = "==2023.12.0"

[environments]
ab-stable = {features = ["ab-stable"], solve-group = "ab-stable"}

as this fails on pixi install and pixi install --environment ab-stable with

  × failed to solve the conda requirements of 'ab-stable' 'linux-64'
  ╰─▶ Cannot solve the request because of: The following packages are incompatible
      ├─ coffea ==2024.4.0 can be installed with any of the following options:
      │  └─ coffea 2024.4.0
      └─ coffea ==2023.12.0 cannot be installed because there are no viable options:
         └─ coffea 2023.12.0, which conflicts with the versions reported above.`

I want to have multiple environments with different versions to be able to debug a script across multiple environments with different installed versions, e.g.:

$ pixi run --environment ab-stable python failing_example.py

[matthewfeickert]

I think the answer as of pixi v0.18.0 is "you don't" and you instead construct multiple environments that work with a very minimal "default" environment like the following:

[project]
name = "columnar-analysis-benchmarks"
version = "0.1.0"
description = "Add a short description here"
authors = ["Matthew Feickert <[email protected]>"]
channels = ["conda-forge"]
platforms = ["linux-64"]

[tasks]

[dependencies]
python = "3.11.*"

[feature.ab-stable.dependencies]
coffea = "==2023.12.0"

[feature.ab-dev.dependencies]
coffea = "==2024.4.0"

[environments]
ab-stable = ["ab-stable"]
ab-dev = ["ab-dev"]

[ruben-arts]

Correct. We actually didn't have an example of this case yet. But the logic dictates the behavior like this. I could think of a situation where you would like to make it "overwrite" the dependencies based on definitions. This however requires the developer to know to overwrite behavior. So not sure if it is worth it to replace this behavior.

One tip:
You can redifine the default environments.

[environments]
default = ["ab-stable"]
ab-dev = ["ab-dev"]

This would create the same ux as your initial example

[matthewfeickert]

I'm not sure off the top of my head when this was added, but in pixi v0.41.4 there is now the concept of non default environments where you explicitly indicate that

the environment not [have] the default feature, and only the features you specify.

In the [environments] table you can indicate this with setting the no-default-feature field to true

[environments]
example = {features = ["example"], no-default-feature = true}