dinamically set env variable

[ZeeD]

Is your feature/enhancement proposal related to a problem? Please describe.

I am starting an airflow project.
I successfully used pdm to install airflow, my dependencies, etc...

my goal is to set AIRFLOW_HOME to a folder of my project (basically I want a layout like the following one)

.../myproject
├── airflow
│   └── dags
...
├── pdm.lock
└── pyproject.toml

and also, I am trying to leverage pdm scripts support.

basically I want to set

[tool.pdm.scripts]
_.env = { AIRFLOW_HOME = ".../myproject/airflow" }
start = { cmd = "airflow standalone" }

but airflow expect an absolute path for AIRFLOW_HOME and I don't want to hardcode that in the pyproject.toml file

Describe the solution you'd like

There are many tricks that could help me, but at the end I want to be able to set an environmental variable dinamically, and not with a literal.

• maybe pdm could expose ${PROJECT_ROOT} as an env variable AND let me set AIRFLOW_HOME = "${PROJECT_ROOT}/airflow"
• or pdm let me invoke a command, so I could write something like AIRFLOW_HOME = "$({pdm} info --where)/airflow"

but at the moment the values are treated as literals

[o-moe]

Have you seen the pdm-dotenv plugin from the awesome-pdm list? Maybe you can utilize it to define your AIRFLOW_HOME and use it with pdm.

[ZeeD]

hi @o-moe , thanks for your suggestion.
I was checking the plugin, but from a cursory look I might have some doubts about its benefits.

Moreso that my understanding is that pdm's [tool.pdm.scripts] section already support the load of a shared custom env file, via _.env_file = ".env"

In any case your suggestion bring me to do some additional tests, and it seems that I can recycle env variables in the .env file. Witch is reasonable, as from my understanding pdm is using python-dotenv under the hood.

But it seems to me that PROJECT_ROOT is not available during the .env analysis, so I'm stuck again, because I cannot retrieve the project full path.
And from what I know python-dotenv doesn't support any kind of process execution in the .env file boy, but maybe I'm wrong.

Do you think there are some paths I've missed?

[ZeeD]

Hi, it's me again.

I've tried to find a workaround, and I've summarized my work on https://github.com/ZeeD/pdm-dotenv-test and indeed it "works": it's possible to just clone the repo, run pdm install once and then pdm run test will show an absolute path using the project folder.

The idea was to leverage pdm-dotenv plugin to pre-load a custom .env.projectroot file. This file is auto-generated after the install of the project locally.

Yet, I have some questions:

• first of all, is the approach sound? I'm not sure I'm doing something "wrong" with the plugins and the event handlers.
• on a technical level, is it correct to leverage the post_install hook to install the pdm-dotenv plugin? it seems to me that pdm install doesn't install the plugin and I don't know why
• for the dotenv_projectroot.py - that is basically just an helper for the initial installation - is there a better folder I should use? I don't want to mix it with the other sources (in src)

In any case, I still think that it would make sense for pdm itself to set the PROJECT_ROOT env variable

[ZeeD]

oh, thanks!