Using Stack for build of Haskell code on Travis CI has

number of benefits. For those unfamiliar with it, Travis is a

cloud-base continuous integration system, which will build and test

your code automatically. It integrates with Github and is free for

open-source projects (but also has paid plans for private

projects). Stack's use of cached packages built from Stackage

snapshots means builds will be much shorter than without, and

reduces the guesswork of whether a build failure was introduced by

your own code or something that changed on Hackage. It's also easy

to use multiple environment configurations to test against multiple

snapshots, including the latest nightly, as a way to ensure that

your code builds against a known-to-work set of the latest

packages.

Stack works very nicely on Travis, but until recently the

documentation for how to set it up languished in semi-obscurity on

the Stack wiki. Hereby, we are lifting it out of obscurity. Rather

than repeat ourselves, go look at:

• The Travis with caching section of the user's guide, which should be sufficient for most use cases.

• The Travis CI document, which has more information and a slightly different approach.