Speeding up Haskell builds on CircleCI

I’ve gotten so used to how awesome continuous integration is I don’t think I could live without it anymore. Unfortunately building Haskell projects was becoming a pain since everything had to be rebuilt each commit.

Now using Circle CI along with stack allows projects to be built in the fraction of the time.

As of commit 60ee51b my circle.yml file looks like this:

This is the configuration file for circleci.com (CI which builds the site)

# Manually install to avoid install conflicts
# cf. https://github.com/jaspervdj/hakyll/issues/340#issuecomment-96101869
dependencies:
  cache_directories:
    - "~/.stack"
  pre:
    - wget https://github.com/commercialhaskell/stack/releases/download/v0.1.10.0/stack-0.1.10.0-linux-x86_64.tar.gz -O /tmp/stack.tar.gz
    - tar -zxvf /tmp/stack.tar.gz --strip 1 -C /tmp/
    - ls -laxo /tmp
    - chmod +x /tmp/stack
    - sudo mv /tmp/stack /usr/bin/stack
  override:
    - stack setup
    - stack build

general:
  branches:
    ignore:
      - compiled-html # actaul website content

# Compile pages during the test stage
test:
  override:
    - make check

Breaking it down

This section tells circleCI to keep this directory around build to build.

dependencies:
  cache_directories:
    - "~/.stack"

This downloads the latest stack release to /tmp of the build container, extracts the package to /tmp, copies the executable to the bin directory, and sets the executable bit on stack.

pre:
  - wget https://github.com/commercialhaskell/stack/releases/download/v0.1.10.0/stack-0.1.10.0-linux-x86_64.tar.gz -O /tmp/stack.tar.gz
  - tar -zxvf /tmp/stack.tar.gz --strip 1 -C /tmp/
  - ls -laxo /tmp
  - chmod +x /tmp/stack
  - sudo mv /tmp/stack /usr/bin/stack

Make sure GHC and all packages declared in .cabal are built.

override:
  - stack setup
  - stack build