[question] Use multiple virtual environments

[Marcin-Radecki]

Hi, we'd like to use both virtualrunenv and virtualenv together when installing a package. We define some environmental variables in a recipe, which needs to be visible by a package consumers - this is done by virtualenv generator. Also we need to use virtualrunenv in order to configure envs like LD_LIBRARY_PATH etc.

I have not found info in the docs that following actually works: conan install -g only supports one virtual environment at a time, but you can pass multiple -g in the same command:

bash-4.2$ conan install package/1.0 -g virtualenv -g virtualrunenv
bash-4.2$ source activate.sh 
(conanenv) bash-4.2$ source activate_run.sh 
(conanrunenv) (conanenv) bash-4.2$ env
# LD_LIBRARY_PATH, PATH and other envs properly configured

My question is where it is an advised way to do so. If yes, do you think it's worth adding such example to official docs?

• I've read the CONTRIBUTING guide.

[memsharded]

Hi @Marcin-Radecki

Conan virtual environment are mostly intended to be composable. What you are doing is the way to go. There might be another approach that is to explicitly add PATH and other variables explicitly in each package package_info() method, and then use only virtualenv generator. But what you are doing is indeed completely fine.

The only caveat is that there are still some pending issues specially regarding how virtualenvs are deactivated, that has some issues. I would advise to simply reset the environment when you are composing virtualenv, while this is fixed.

Moving this to the docs repo, it could be worth adding some example there too. Thanks for the feedback!

[Marcin-Radecki]

Hi @memsharded , just one more comment with regards to composing multiple environments: I noticed in Conan 1.21.0 that both activate.sh and activate_run.sh contain below line

export CONAN_OLD_PATH="$PATH"

whereas both deactive.sh and deactivate_run.sh have following line:

export PATH="$CONAN_OLD_PATH"
unset CONAN_OLD_PATH

That means that even though composing virtual environments works, decomposition of them does not - in addition to an exmaple in my first message:

(conanrunenv) (conanenv) bash-4.2$ source deactivate_run.sh 
(conanenv) bash-4.2$ source deactivate.sh 

The last line is deliberately empty - the second deactivate.sh breaks up bash prompt, as it tries to set PS1 with an empty string. Moreover, the PATH and broken too as it becomes empty, whereas it should become a value before first activate.sh was run.