Feature/esm export

[ckcr4lyf]

A bug in either node/cjs lexer causes ES6 imports of CJS to fail in some shared environments (steps to reproduce are including in the issue I made here -> nodejs/node#42222)

Although this should ultimately be "solved" in node itself, I was wondering if this ESM export is a potential step dotenv is willing to take.

I'd opened a discussion (Related to this issue - #640), but didn't get any feedback, so thought an MR might be the next step.

This does fix the memory issue for me, when I install dotenv from my fork.

[motdotla]

Thanks for the PR @ckcr4lyf. One concern we have with this is maintaining 2 files that essentially implement the same thing here.

Thoughts on that?

[ckcr4lyf]

I agree, this MR specifically probably isn't the best solution since it leads to duplication with manual copy paste, and maintaining changes as such.

In some of my research, I came across tsup which can bundle the same typescript source into both ESM and CJS.

However considering the size & popularity of dotenv, I was guessing it's been a conscious decision to not introduce compilation from typescript (though it is already a dev dependency). If you are open to the idea, I would be happy to explore a typescript source based build step which leads to producing both esm and cjs form a single source file!

[motdotla]

Your guess is right. We'd rather not get into a build process. Copy/paste isn't the worst thing.

We'll let this sit right now and will consider it over the next few weeks.

Anyone else please chime in with your thoughts as well.

[ckcr4lyf]

Btw: Got feedback from node team - they say this is "intended behavior" - i.e. the lexer for using CJS in ESM reserves a lot of memory, which means in restricted ulimit environments it will not run - nodejs/node#42222 (comment)

So I think at the moment, for anyone using dotenv in a "pure ESM" project (i.e. excluding dependencies), that needs to be run in shared environments with ulimit restrictions, an ESM export fork is required.

[ckcr4lyf]

Update: guybedford over at node team added a fallback parser for importing CJS in an ESM package via nodejs/node#43612

So on latest node (v18.6.0) I do not have this issue with dotenv. Since it is an official release, I will close this MR for now, though I do think it would be nice to have an ESM export for dotenv in the future.