HLint on Travis/Appveyor

Summary: Running HLint on your CI is now quick and easy.

I've always wanted to run HLint on my continuous integration servers (specifically Travis for Linux and Appveyor for Windows), to automatically detect code that could be improved. That has always been possible, and packages like lens and freer-effects have done so, but it was unpleasant for two reasons:

• Setting up a custom HLint settings file and applying these settings was a lot of upfront work.
• Building hlint on the CI server could be quite slow.

With HLint v2.0.4, both of these issues are addressed. I am now running HLint as standard for many of my projects. The two steps are outlined below.

Setting up custom HLint settings

Locally run hlint . --default > .hlint.yaml and it will generate a file which ignores all hints your project currently triggers. If you then run hlint . there will be no warnings, as the ignore settings will automatically be picked up. Check in .hlint.yaml.

Later, as a future step, you may wish to review your .hlint.yaml file and fix some of the warnings.

Running HLint on the server

There are now precompiled binaries at GitHub, along with scripts to download and execute them for each CI system. In both cases below, replace ARGUMENTS with your arguments to hlint, e.g. . to check the current directory.

On Travis, execute the following command:

wget https://raw.github.com/ndmitchell/hlint/master/misc/travis.sh -O - --quiet | sh -s ARGUMENTS

On Appveyor, add the following statements to .appveyor.yml:

- set PATH=C:\Program Files\Git\mingw64\bin;%PATH%
- curl -ohlint.bat -L https://raw.githubusercontent.com/ndmitchell/hlint/master/misc/appveyor.bat
- hlint ARGUMENTS

Since these are precompiled binaries the additional time required to run HLint should be minimal.