Command Substitution

[nVitius]

I added code to this plugin to do command substitution like bash does: $(some_command)

My personal use case was that I wanted to have the version from package.json inside of a env var in my Vue app.
Using this update, you can do something like: APP_VERSION="$(cat package.json | jq '.version')"

I've added a simple test (using echo) and made sure that all other existing tests are still working.
I think this could be a really valuable addition to the plugin.

[Heziode]

You should add an option to allow enable/disable this feature, because the execution of command can be dangerous.

[nVitius]

@Heziode The easiest solution that occurs to me is adding a prefix to the keys. Something like: EVAL_APP_VERSION

What do you think?

[Heziode]

IMHO, it should be done with an option inside the conf object, like this:

dotenv-expand/lib/main.js

Line 5 in de9e5cb

var environment = config.ignoreProcessEnv ? {} : process.env

This will also require to update the inde.d.ts (that also have a missing value that wil be fixed with #47):

dotenv-expand/index.d.ts

Lines 3 to 8 in de9e5cb

	interface DotenvResult {
	error?: Error;
	parsed?: {
	[name: string]: string;
	};
	}

[nVitius]

My issue with using the config object is that some of the popular bundlers (namely vue-cli and parcel) use dotenv (and dotenv-expand) but don't expose any way to pass configuration options into it.

Also, dotenv itself doesn't seem to officially support custom config values like ignoreProcessEnv
Reference: https://github.com/motdotla/dotenv/blob/72fb66b051280ef5c2cc40ce4962ac4601f7f515/lib/main.js

At least, they aren't included in the type definition.

[Heziode]

My issue with using the config object is that some of the popular bundlers (namely vue-cli and parcel) use dotenv (and dotenv-expand) but don't expose any way to pass configuration options into it.

Indeed, I hadn't thought of that. Afterwards, nothing prevents you from adding it to your project.

For implemenation details, etc. I think that @motdotla is more relevant to answer, since it's his lib.

[cryptiklemur]

Why not use the config value, with a fallback to an env variable itself if not set

DOTENV_EVAL=false or something

[nVitius]

@motdotla
Can we get your feedback on this PR please?

[motdotla]

@nVitius thank you so much for this contribution 💛

That said, we decided to move it to its own module here: https://github.com/motdotla/dotenv-eval

We should see that module grow in complexity as it handles any edge cases.

[nVitius]

@motdotla a lot of projects use dotenv through an external tool and don't have access to configure dotenv or add new dependencies. I use dotenv a lot in my vue projects and vue-cli handles loading in dotenv. There would be no way for me to leverage command substitution in this case. Have you given any thought on how that might be solved for?

[motdotla]

@nVitius very good point.

So does vue-cli already default include dotenv-expand?

[motdotla]

(a part of me is also starting to think that maybe expand's functionality should move directly into Dotenv's)

[Heziode]

(a part of me is also starting to think that maybe expand's functionality should move directly into Dotenv's)

This is exactly what I did, when I rewrote your lib in Ada: https://github.com/Heziode/ada-dotenv

[ccmattr]

(a part of me is also starting to think that maybe expand's functionality should move directly into Dotenv's)

It would be amazing if dotenv-expand and dotenv-eval could be included by default. Theres no reason to say the package users couldnt limit the functionality through configuration.