Add feature to dynamically set environment variables in `envs.ENV.env-vars`

[ketozhang]

Discussed in https://github.com/pypa/hatch/discussions/1554

^{Originally posted by ketozhang June 6, 2024} Is there any way to dynamically set environment variables?

In my use case, I want to set a secret variable dynamically using a command that takes in another env var for the secret key/name.

[tool.hatch.envs.default.env-vars]
SECRET_KEY="some-key-name"
SECRET="$(get-secret $SECRET_KEY)"  # get-secret is a placeholder command

The only way I can think of is to set it in scripts.

[tool.hatch.envs.default.scripts]
test="SECRET=$(get-secret $SECRET_KEY) printenv"

...which does not scale, unless you can use secret="export SECRET=..." then test=["secret", "printenv"], but I don't think hatch preserves export.

[ofek]

Out of curiosity, does that workaround I mentioned in that discussion work for you (temporarily)?

[ketozhang]

Yes it does–thank you!

[johnpyp]

Just to note for other readers until a better solution is put in place, you can currently do this by creating an Environment Collector plugin which can arbitrarily edit the env vars of all environments.

[sebag90]

based on @johnpyp's suggestion I created a plugin to automatically collect variables from a .envfile and set it to all hatch environments:

from pathlib import Path
import re

from hatch.env.collectors.plugin.interface import EnvironmentCollectorInterface


class EnvVarSetter(EnvironmentCollectorInterface):
    def finalize_environments(self, config):
        env_file = Path(".env")
        if not env_file.exists():
            return config

        # collect new env vars in .env
        new_vars = dict()
        pattern = re.compile(r"""^([^\s=]+)=(?:[\s"']*)(.+?)(?:[\s"']*)$""")
        with env_file.open(encoding="utf-8") as infile:
            for line in infile:
                match = pattern.match(line)
                if match is not None:
                    new_vars[match.group(1)] = match.group(2)

        # add new env vars
        for env_name, env_entry in config.items():
            if not env_name.startswith("hatch"):
                if "env-vars" not in env_entry:
                    env_entry["env-vars"] = new_vars
                else:
                    env_entry["env-vars"].update(new_vars)

        return config

and then simply add this to your pyproject.toml:

[tool.hatch.env.collectors.custom]
path = "path/to/envvarsetter.py"

I guess the plugin can be easily modified to set other variables