How to use [activation] with [tasks]?

[matthewfeickert]

A colleague of mine has a (org internal repo, sorry) pixi.toml of the following

[project]
name = "Run3ModelGen"
version = "0.1.1"
description = "Add a short description here"
authors = ["My colleague <their email>"]
channels = ["conda-forge"]
platforms = ["linux-64", "osx-64", "osx-arm64"]

[tasks]

build = """
cmake -S source -B build && \
cmake \
    --build build \
    --clean-first \
    --parallel 4
"""

genModels = """
. build/setup.sh && \
mkdir run && \
cd run && \
genModels.py
"""

[target.linux-64.tasks]
# Use nproc as available
build = """
cmake -S source -B build && \
cmake \
    --build build \
    --clean-first \
    --parallel "$(nproc --ignore=1)"
"""

[dependencies]
python = "3.11.*"
gfortran = ">=13.2.0,<13.3"
cmake = ">=3.29.2,<3.30"
numpy = ">=1.26.4,<1.27"
pyyaml = ">=6.0.1,<6.1"
make = ">=4.3,<5"
which = ">=2.21,<3"

[target.linux-64.dependencies]
gcc = ">=13.2.0,<13.3"
cxx-compiler = ">=1.0.0,<1.1"

[pypi-dependencies]
pyslha = ">=3.2.6"
uproot = ">=5.3.3"

However, after running

$ pixi run build

to build the unpackaged C++ dependencies acquired via Git, pixi run genModels fails with:

$ pixi run genModels 
✨ Pixi task (genModels in default): . build/setup.sh && mkdir run && cd run && genModels.py

.: command not found

Available tasks:
	build
	genModels

as the shell that pixi run uses isn't one that understands . as a source command(?).

pixi does support activation scripts with [activation], but how would one write the TOML to specify an activation script for a specific task in an environment?

[ruben-arts]

Currently this is not possible. The latest release does support setting environment variables per task:

[tasks]
run = { cmd="python run.py $ARGUMENT", env={ ARGUMENT="value" }}

But that might only marginally help.

The other solution would be to run a shell in the pixi task e.g.:

[tasks]
hello = "bash -c 'source env.sh && echo $HELLO'"

# env.sh file
export HELLO="Hello, World!"

This can obviously go wrong, but you could make these tasks per target to make them a little more safe.

[matthewfeickert]

Thanks @ruben-arts.

The other solution would be to run a shell in the pixi task

I think this is probably the best way forward for the time being (in pixi v0.21.0).

Currently this is not possible

Are there any plans to implement something like this in the future? Or is this not a goal for the pixi task runners in general?

[ruben-arts]

I could see support for that coming to the tasks yes, and it shouldn't be to hard as we already do the activation anyway.

[tacaswell]

I have a very similar problem, but I need to pass different env depending on the platform (in my case setting different CC and CXX on windows) so hard coding the env is not enough.

[matthewfeickert]

@ruben-arts is this in any way connected to the limitations of the deno shell currently used, and might be affected by https://github.com/prefix-dev/shell in the future? Or is this unrelated and would required additional new features in pixi?

[ruben-arts]

This is on pixi's side, this constantly gets rained down by other features. Would definitely be open for a design discussion and get the feature contributed by the community to get this in sooner!