The instructions below are the explicit way of creating and pushing a production or development build. Have a look at the npm scripts I've provided to make this process simpler.
You should know and understand how to create and run a Google Apps Script. If you haven't built a Google Apps Script before, then stop here and go through Google's official tutorials. Then, I also highly recommend you work through the video tutorial series from 'Learn Google Spreadsheets'.
As a first step, I suggest you try building your first script using the default source file, and the npm script prod. This way, you can be confident that you understand the steps necessary to develop and run a script using Google's command-line interface clasp. The npm scripts create, followed by prod will create a spreadsheet and a script cljs-gas-app-example. The source file for this script, core.cljs will log "Hello cljs from GAS with clasp" to the script console and write "I don't do anything yet! to cell A1". To run this script, find the cljs-gas-example spreadsheet in your Google Drive folder, select Tools->Script Editor and, from the script editor, select Run.
npm installto install the clasp cli toolsnpx clasp loginto login to and authorize the Clasp Apinpx clasp create --title <title> --type <type> --rootDir ./exportto create the spreadsheet and script.
Any code that you write for Google's Workspace API must be uploaded and executed on Google Servers. Therefore, developing and testing locally is limited. Forget about a REPL, your feedback cycle is now: compile, upload (using the clasp push command) and debug using console.log debugging. You could mock out the parts of Google's API (see Laurent Charignon's blog post for an example approach. But that's a lot of work for a questionable return.
The following will compile the source files using the map from dev.ednthe map from dev.edn. The differences from build.edn are {:pseudo-names :true} with {:pretty-print true}. With this configuration, your apps script function names and lines are preserved, in case there is a function missing from resources/gas.ext.js externs file. Then, add an externs entry for this missed case.
$ npm run dev
...
# After successful compiliation
# push your dev build (i.e., Apps Script) to your Google Drive folder
$ npm run push
The following will compile the src directory files once, using {:mode :advanced}, {:pseudo-names false}, and {:pretty-print false}. Then, push your Apps Script export/Code.gs to your Google Drive folder.
$ npm run build
...
# After successful compiliation
# push your dev build (i.e., Apps Script) to your Google Drive folder
$ npm run push
Pull requests are welcome.