Digital Ocean App Platform tsc command not found

When trying to deploy my node app on Digital Ocean’s App Platform, the build failed and the error was:

tsc: command not found

Here is what my build command was

"build": "tsc"

Apparently I needed to install the dev dependencies, so using

"build": "npm install --only=dev && tsc"

worked

Here are some community posts discussing this:

https://www.digitalocean.com/community/questions/app-platform-keeps-using-cached-node_modules-despite-changes

https://www.digitalocean.com/community/questions/how-do-you-use-node-js-devdependencies-in-the-app-platform-builds