what is config supposed to be in this context?

yes, you can do almost everything in a build hook but I don't quite have enough information to give an answer

ClassNotFoundException config is a bit weird, so not sure about that one. would help to know what config is supposed to be?

I have a file like config.cljs where I defined some env variables like (goog.define GRAPHQL_URL "") which in turn are overwritten by the compiler with

:release
{:closure-defines
 {config/GRAPHQL_URL         "url"

the file is like $company-name-space.web.config.cljs

ok there is so many issues with this description. please be mindful of the names and descriptions

so I suppose the really actual filename is $company-name-space/web/config.cljs?

and its actual ns is $company-name-space.web.config?

and use are using goog-define and not goog.define?

and then what are you trying to do with that value inside a build hook?

issue one: config/GRAPHQL_URL is not correct. it needs to use the full namespace, so $company-name-space.web.config/GRAPHQL_URL

issue two: what is the purpose of this build hook? you can already define separate development/release values, just via the config? (which appear to already use given the :release key?)

I'm sorry for the issues in the description, I'll be more accurate the next time. The use case I have is that we have to create different snippets of javascript code to inject in the index.html depending on the value of the build: so if it's :release we use a an id for the google analytics snippet, whereas if it's :dev we use another value so that the metrics of the apps are different for production and stage. Right now the problem I'm facing is that I can't reference the value of the google analytics id as env variable and use that env variable inside the hook. Maybe it's possible and I just misunderstood the way hooks and env vars works in shadow. The workaround I found out was to declare the value of those ids in the hooks file and change it depending on the value of the build, but ideally I'd prefer to use the env var if possible. I don't know if with this explanation it makes more sense. Thanks for replying anyway, I really appreciate your support!

so, this build hook is generating the index.html?

You can reference any environment variable via (System/getenv "THAT_VARIABLE"), if you mean actual system environment variable

hooks run clojure code, so it is not CLJS (which doesn't have access to environment variables directly)

for CLJS you can use https://shadow-cljs.github.io/docs/UsersGuide.html#shadow-env in the build config though

no, the hook is not generating the index.html , but is creating a JavaScript file that is referenced in the index.html

and btw, I don't know if this is a proper way to use the hooks in shadow, but I found it pretty cool and useful!

no, it is not recommended use of build hooks

anything that could just be a function since it didn't need any access to the build state should just be a function 😛

well in this case I thought I needed the access to the build state to use and id or another depending on :dev or :release but I see your point 😄

anyway, in the company where I work we're almost done migrating our project from an old figwheel config to shadow, it's been very interesting to migrate the project and shadow it's amazing, thank you for your work!

FWIW this is what I mean https://shadow-cljs.github.io/docs/UsersGuide.html#clj-run. create a regular function here. call it from a function like this.

Interesting, I wasn't aware of this case, will look into it