Heroku Buildpack for Stack

Heroku buildpack for Stack. Based on the excellent heroku-buildpack-ghc

Usage

Create an app with this buildpack:

$ heroku create --buildpack https://github.com/mfine/heroku-buildpack-stack.git

Set this buildpack on an existing app:

$ heroku buildpacks:set https://github.com/mfine/heroku-buildpack-stack

Binary executables are placed in /app/.local/bin/ after compilation, a directory which Heroku includes in your $PATH, so assuming that your application is binding to $PORT, you can serve your app by creating a Procfile at your project root that defines a web process type for the executable defined in your .cabal file:

$ cat *.cabal | grep executable
executable YOURAPPNAME-exe

$ echo "web: YOURAPPNAME-exe" >> Procfile

Templating stack.yaml

To avoid committing secrets into stack.yaml for access to private repos, an app's config vars values can be substituted for tags enclosed in double brackets. For example, given a stack.yaml containing:

packages:
-location:
    git: https://mfine:{{GITPASS}}@github.com/mfine/heroku-buildpack-stack.git

and an application with config vars:

$ heroku config -app calm-storm-51595
=== murmuring-beyond-51595 Config Vars
GITPASS: abc123
$

before compilation, the stack.yaml will be substituted as follows:

packages:
-location:
    git: https://mfine:abc123@github.com/mfine/heroku-buildpack-stack.git

Makefile Support

This buildpack now supports an optional Makefile, in case you need to coordinate other build steps with Stack. It assumes that the Makefile includes a make install target that uses the Stack build command with the flag --copy-bins. For example, a possible install target configuration in the Makefile could be:

install:
    stack build --copy-bins