Clojurians Log v2

Is there a way to set the environment variable before lein test runs?

MYENV=1 lein test ?

There are plugins that set environment variables, I don't know which is best though. Environment variables are sadly not first class at all in the jvm without third party extensions with limited cross platform support.

@noisesmith Could you recommend one or two which would do this? I am looking for something that I can configure like this

:profiles {:test {:env {"MYENV" "test"
                  :dependencies [[ring/ring-mock "0.4.0"]]}}

lein-environ should work https://github.com/weavejester/environ#installation - it's not the only option though, I can't tell you which is better

note there's a lib and a plugin, for what you want the plugin is mandatory

(lein can only set the env vars by launching a second vm, that's what the plugin is for)

You can be super hacky and set Java env variables at runtime in an impl-dependent way (that happens to work across any version in recent history that I’ve seen):

(defn set-env! [env-name env-val]
  (let [e (System/getenv)
        cl (.getClass e)
        field (doto (.getDeclaredField cl "m")
                (.setAccessible true))
        em (.get field e)]
    (.put em env-name env-val)))

oh, wow...

@mikerod Is it possible to set this before lein test starts?

I wonder if this works on windows (my understanding was that the jvm lacked setenv because win lacked that API...)

How do you use those env vars? Can system properties be used instead? (I do this with our config tests)

lein-env, linked above, supports this. And something multiple libraries offer is a merge of config from a file, the environment, and jvm system properties, so that you can set things via env in prod, and use files and programmatic property setting for local dev.

env and aero each support some variant of that

@danisam17 yeah, it could be done as a :prep-tasks or something probably. I’m not sure this is the best approach to do things - I’ve used it but only in a testing tool with important caveats that I verified it worked on like JDK8 through 11 so far on an OpenJDK based JVM

the funny part of Java’s env variables is just that they are loaded and stored in a mutable hashtable

and after that - that’s the Java “source of truth”

so you can mutate it… (of course this does require open security priv’s, which you’d have in cases where you’re running the system etc)

oh so that technique isn't actually changing the process environment, just the mutable table that's used to look it up?

yep