Confusion around util.env and util.tryEnv in preflight vs inflight contexts

[skyrpex]

The util.env and util.tryEnv utilities work differently in preflight and inflight contexts.

Given the following example:

MY_VAR=123 wing compile main.w

// main.w
bring cloud;
bring util;

log(util.env("MY_VAR")); // Logs 123
let MY_VAR = util.env("MY_VAR");

new cloud.Function(inflight () => {
  log(util.tryEnv("MY_VAR") ?? "<no value>"); // Logs <no value>
  log(MY_VAR); // Logs 123
});

The Cloud Function util.tryEnv is being translated into a lookup to process.env rather than use the host's environment variables. I find this behaviour confusing, maybe even unnecessary. Do we need to access environment variables in inflight functions? The only environment variables we can specify are when invoking the Wing CLI.

IMO, log(util.tryEnv("MY_VAR") ?? "<no value>"); should log 123 as well, with the actual inflight code being inlined as log("123" ?? "<no value>"); (it could even be simplified to log("123")).

[eladb]

Let's start by restricting util.env() to preflight.

It feels like the right direction and one can always assign the value to a preflight variable and capture it:

let myEnv = util.env("MYENV");

inflight () => {
  log(myEnv);
};

Thoughts? Too restrictive?

[skyrpex]

It makes sense to me 👍.

[eladb]

@Chriscbr do we have a way to mark a utility API as "only preflight"?

[github-actions]

Hi,

This issue hasn't seen activity in 60 days. Therefore, we are marking this issue as stale for now. It will be closed after 7 days.
Feel free to re-open this issue when there's an update or relevant information to be added.
Thanks!

[boyney123]

Hey!

Just coming to this from a winglib I'm trying to make for stripe (winglang/winglibs#279).

I literally just come across some of this confusion, trying RANDOM=true wing test and expecting the variable to be accessible in my inflight code (using util.env and util.tryEnv) but no luck, as ofc it's inflight code.

Having it preflight only makes sense, only after I got my head around a few things (thanks @Chriscbr!), but I do wonder people coming from other languages, if it's too restrictive or unintuitive? I expected it to be in both preflight and inflight, this extra layer of cognitive load thew me off abit 🤷‍♂️

[Chriscbr]

Let's start by restricting util.env() to preflight.

It feels like the right direction and one can always assign the value to a preflight variable and capture it:

let myEnv = util.env("MYENV");

inflight () => {
  log(myEnv);
};

Thoughts? Too restrictive?

I think this solution makes sense to me, especially in lieu of the confusion David and other users have run into trying to access environment variables in inflight code. The current design where util.env is a phase-independent function that retrieves an environment variable in the phase this function was called seemed ok to me in the past, but I don't think it's helping people fall into the pit of success.

(Let's make sure util.tryEnv is also preflight-only as well)

[eladb]

Let's do it