by flocabulary

GitHub Readme.md

Post-build Clean Buildpack

A simple buildpack to run after all other buildpacks have completed, which removes a set of files defined in .slug-post-clean, so that they are not included in the finished slug.


While this may seem to duplicate functionality provided by Heroku's .slugignore, there is a key difference: .slugignore'd files are removed after the repo is cloned, but before any buildpack is run. They can therefore not be involved in the build process itself.

However, it is not uncommon for there to exist files in the repo that are necessary for the build, but are not required at runtime. There may also be installable build dependencies that are not runtime dependencies.

In our case, a complex front-end build involves significant CSS, JS and image assets, along with a large installation of node modules, all of which are used only for building the production assets, but then remain part of the slug.


You will need to use multiple buildpack. The post-build-clean buildpack must be last in the buildpack order, and a Procfile is required for Heroku to correctly identify the process types (otherwise last buildpack in the list will be used to determine the process types for the application).

Artifcats list

The .slug-post-clean file supports single-file and single-directory declarations only, e.g.:


Notice that an empty ending line will be required.

It might be expanded to support file globs, but for the moment it's not necessary and the testing implications give me the willies.