Travis CI

This page documents how to use Stack on Travis CI. We assume you have basic familiarity with Travis. We provide two fully baked example files ready to be used on your projects:

  • The simple Travis configuration is intended for applications that do not require multiple GHC support or cross-platform support. It builds and tests your project with just the settings present in your stack.yaml file.
  • The complex Travis configuration is intended for projects that need to support multiple GHC versions and multiple OSes, such as open source libraries to be released to Hackage. It tests against cabal-install, as well as Stack on Linux and macOS. The configuration is significantly more involved to allow for all of this branching behavior.

NOTE: It is likely going to be necessary to modify this configuration to match the needs of your project, such as tweaking the build matrix to alter which GHC versions you test against, or to specify GHC-version-specific stack.yaml files if necessary. Don't be surprised if it doesn't work the first time around. See the multiple GHC section below for more information.

Each of these configurations is ready to be used immediately, just copy-paste the content into the .travis.yml file in the root or your repo, enable Travis on the repo, and you're good to go.

You may also be interested in using AppVeyor, which supports Windows builds, for more cross-platform testing. There's a short blog post available on how to do this.

The rest of this document explains the details of common Travis configurations for those of you who want to tweak the above configuration files or write your own.

Note: both Travis and Stack infrastructures are actively developed. We try to document best practices at the moment.

Container infrastructure

For Stack on Travis to be practical, we must use caching. Otherwise build times will take an incredibly long time, about 30 minutes versus 3-5. Caching is currently available only for container-based Travis infrastructure. Shortly we have to add

sudo: false

# Caching so the next build will be fast too.
cache:
  directories:
  - $HOME/.stack

To the .travis.yml. This however restricts how we can install GHC and Stack on the Travis machines.

Installing Stack

Currently there is only one reasonable way to install Stack: fetch precompiled binary from the Github.

before_install:
# Download and unpack the stack executable
- mkdir -p ~/.local/bin
- export PATH=$HOME/.local/bin:$PATH
- travis_retry curl -L https://www.stackage.org/stack/linux-x86_64 | tar xz --wildcards --strip-components=1 -C ~/.local/bin '*/stack'

Installing GHC

There are two ways to install GHC:

  • Let Stack download GHC
  • Install GHC using apt plugin

See the above scripts for an example of the first option (letting Stack download GHC). Here, we will explain the second option. With single GHC the situation is simple:

before_install:
  # Install stack as above
  # ...
  # Configure stack to use the system GHC installation
  - stack config set system-ghc --global true
  - export PATH=/opt/ghc/7.10.2/bin:$PATH

addons:
  apt:
    sources:
    - hvr-ghc
    packages:
    - ghc-7.10.2

Multiple GHC - parametrised builds

Travis apt plugin doesn't yet support installing apt packages dynamically (https://github.com/travis-ci/travis-ci/issues/4291). That for we need to write a bit repetitive .travis.yml.

Also for different GHC versions, you probably want to use different stack.yaml files.

# N.B. No top-level env: declaration!

matrix:
  include:
  - env: GHCVER=7.8.4 STACK_YAML=stack.yaml
    addons:
      apt:
        sources:
        - hvr-ghc
        packages:
        - ghc-7.8.4
  - env: GHCVER=7.10.1 STACK_YAML=stack-7.10.yaml
    addons:
      apt:
        sources:
        - hvr-ghc
        packages:
        - ghc-7.10.1
  - env: GHCVER=head STACK_YAML=stack-head.yaml
    addons:
      apt:
        sources:
        - hvr-ghc
        packages:
        - ghc-head
  allow_failures:
    - env: GHCVER=head STACK_YAML=stack-head.yaml

before_install:
  # ghc
  - export PATH=/opt/ghc/$GHCVER/bin:$PATH

Especially to use ghc HEAD you need to pass --skip-ghc-check option to Stack.

Running tests

After the environment setup, actual test running is simple:

script:
  - stack --no-terminal --skip-ghc-check test

In case you're wondering: we need --no-terminal because stack does some fancy sticky display on smart terminals to give nicer status and progress messages, and the terminal detection is broken on Travis.

Other details

Some Stack commands will run for long time (when cache is cold) without producing any output. To avoid timeouts, use the built in travis_wait.

install:
  - travis_wait stack --no-terminal --skip-ghc-check setup
  - travis_wait stack --no-terminal --skip-ghc-check test --only-snapshot

Examples

Future enhancements

Once Travis whitelists the stack .deb files, we'll be able to simply include stack in the addons section, and automatically use the newest version of stack, avoiding that complicated before_install section This is being tracked in the apt-source-whitelist and apt-package-whitelist issue trackers.