Node.js now installs `devDependencies` by default
Change effective on 01 March 2018
Many users getting started with Node.js on Heroku run a
build step with webpack, ng-cli, or another build tool
only to find that it’s in their devDependencies and
therefore not installed by default on Heroku.
We’ve updated the default behavior to install all
dependencies listed in package.json during build, and to
strip out the developer dependencies before the app is
deployed.
Visit Dev Center to learn how you can customize this behavior
You will see a new section in your logs where we prune the
devDependencies:
$ git push heroku master
...
-----> Pruning devDependencies
removed 24 packages in 0.241s
...