jfmengels' blog

Jeroen Engels

Written by Jeroen Engels, author of elm-review. If you like what you read, you can follow me on Twitter or sponsor me.

Great compiler messages? Great test failure messages!

February 18, 2021

If you’ve written a little bit of Elm code, I hope you’ve tried out which allows you to write and run tests for your Elm code (if you never…

Safe dead code removal in a pure functional language

January 28, 2021

A few months ago, a colleague of mine wrote this on Slack: Thanks to elm-review I was able to remove ~7300 lines of code in the front end in…

Test-only values

December 22, 2020

Opaque types is a great technique in Elm. It prevents misuse of a custom type by restricting the possible operations you can apply to it…

1 year of elm-review. What lies ahead?

September 29, 2020

elm-review v1 was released on September 29th 2019. Today therefore marks the first anniversary of its release! 🥳🎉 Ambitions I have pretty…

Hacktoberfest 2020

September 29, 2020

Hacktoberfest will be starting in two days, and it’s a good opportunity to get started in open-source and help out the projects you like or…

2.3.0 - Just try it out

September 08, 2020

This is going to be another simultaneous release for both the CLI and the Elm package. Both bring what I think are very exciting features…

What has happened since elm-review v2?

August 26, 2020

I am in the final preparations for a new (and exciting) release of , and I noticed I didn’t communicate all the changes that happened since…

Single out elements using phantom types

May 04, 2020

Today, I will showcase a technique to single out elements from a type, through the medium of a puzzle (which you can try to solve or ignore…

Safe unsafe operations in Elm

April 27, 2020

In Elm, we often have modules around a data type which needs a validation when you initially create it. For instance, the package defines a…

elm-review v2!

April 08, 2020

Today I am very excited to release 2.0.0 and to share its new features! tl;dr: Here is the list of the introduced features: New review…

Announcing elm-review

September 29, 2019

I am happy to announce the release of and its CLI. What is elm-review? is a tool that analyzes your project’s Elm code, and reports…

The API of a water tap

January 02, 2019

Let’s say we wanted to represent a water tap. This tap will have two knobs, one to control cold water output and another one for warm water…