.travis.yml

# NB: don't set `language: haskell` here

# explicitly request legacy non-sudo based build environment
sudo: required

# The following enables several GHC versions to be tested; often it's enough to test only against the last release in a major GHC version. Feel free to omit lines listings versions you don't need/want testing for.
env:
 - CABALVER=1.24 GHCVER=8.0.2
 - CABALVER=2.0 GHCVER=8.2.2
 
# Note: the distinction between `before_install` and `install` is not important.
before_install:
 - travis_retry sudo add-apt-repository -y ppa:hvr/ghc
 - travis_retry sudo apt-get update
 - travis_retry sudo apt-get install libcairo2 libpango1.0-0 libpangomm-1.4-dev
 - travis_retry sudo apt-get install happy-1.19.4 alex-3.1.3
 - export PATH=/opt/alex/3.1.3/bin:/opt/happy/1.19.4/bin:$PATH
 - travis_retry sudo apt-get install cabal-install-$CABALVER ghc-$GHCVER # see note about happy/alex
 - export PATH=/opt/ghc/$GHCVER/bin:/opt/cabal/$CABALVER/bin:$PATH

install:
 - cabal --version
 - echo "$(ghc --version) [$(ghc --print-project-git-commit-id 2> /dev/null || echo '?')]"
 - travis_retry cabal update
 - cabal install --only-dependencies --enable-tests --enable-benchmarks

# Here starts the actual work to be performed for the package under test; any command which exits with a non-zero exit code causes the build to fail.
script:
 - if [ -f configure.ac ]; then autoreconf -i; fi
 - cabal configure --enable-tests --enable-benchmarks -v2  # -v2 provides useful information for debugging
 - cabal build   # this builds all libraries and executables (including tests/benchmarks)
 - cabal test
 - cabal check
 - cabal sdist   # tests that a source-distribution can be generated

# Check that the resulting source distribution can be built & installed.
# If there are no other `.tar.gz` files in `dist`, this can be even simpler:
# `cabal install --force-reinstalls dist/*-*.tar.gz`
 - SRC_TGZ=$(cabal info . | awk '{print $2;exit}').tar.gz &&
   (cd dist && cabal install --force-reinstalls "$SRC_TGZ")