I have an API key that I don’t want to commit to my source control. What is the best way to “inject” values at compile time? Ideally different values for dev and prod builds. I could find anything in the re-frame and shadow-cljs docs. I found https://shadow-cljs.github.io/docs/UsersGuide.html#closure-defines but they seem also to be static in the config files.

you can override it dynamically via https://shadow-cljs.github.io/docs/UsersGuide.html#config-merge

but I generally recommend keeping "runtime configuration" out of the build completely and instead actually configure it at runtime

eg. you set <script>_APP_CONFIG = {key: "foo"};</script> in your HTML and access it via js/window.MY_APP_CONFIG.key in your code

many different ways to go about this

Sorry I think I am being slow. > eg. you set <script>http://window.MYAPPCONFIG = {key: “foo”};</script> in your HTML Doesn’t that require me to put it into my repo again?

--config-merge seems to be something I can do on my build server with env variables. Do you recommend against doing that?

sorry I was assuming you have some server-side that generates the HTML

No sorry, so far I am working on a plain old client-side SPA

if you really want to turn it into a compile time constant then you can. either --config-merge or env vars work

you can also load the config dynamically at runtime if you don't want to put it into the HTML

as I said ... many different ways to go about this. don't know enough about your app to know what would work for you.

Yeah, maybe a bit more context is useful. I want to write a little authenticated multi collaborator ToDo app, but I want to make it open source. Therefore I don’t want to commit my authentication pool Ids (Using AWS Cognito) to the repository. But ideally provide a simple step on how anyone could create their own user pool and set their ids.

well I would still put it into the HTML that way I think

eg. you create an index.sample.html with some instruction on what to do with it to create the "real" index.html

and just don't put your index.html into the repo?

or you put it into an env var, it is up to you really

I generally advise to keep runtime configuration out of the build

and this is runtime configuration

Nice, I like that. I could also make the script it’s own file and provide a sample. Then it should be relatively easy to provide the real file on a build server. Thank you for your help, I’ll see how I get on 🙂