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Migration from v1 to v2


If you are trying to run v1 of the elm-review CLI and it suddenly stopped working, I am very sorry about that!

Fortunately, there is an easy fix: updating the CLI to version 1.0.2.

npm install -D elm-review@1.0.2

The problem is that previous versions try to build an application behind the scenes, and installs the jfmengels/elm-review package every time. Those versions were not saying which version of jfmengels/elm-review to use though, due to limitations of what elm install offered and elm-json offered at the time.

And now that v2 has been released, well it may well try to install a version of jfmengels/elm-review that doesn't work for your project.

But elm-json's author @zwilias was very responsive to this need, and version 1.0.2 now installs jfmengels/elm-review 1.0.0 <= x < 2.0.0. So kudos to him!

Rule writing

The API for the rules you created in v1 is pretty much the same in v2.

The differences are mostly functions and types that were renamed, and a single argument somewhere to add.

You fortunately won't have to change anything in the logic of your rule or tests.

There are a lot of other API changes not related to creating rules, which are related to making everything work for the CLI. I am not going to describe these here because it's unlikely that someonetiuched that. If I am wrong about this and you did depend on these APIs, come talk to me or open an issue.

Review configuration

Folder structure change

The default folder structure has been updated, therefore I recommend removing your review/ folder (at least the ReviewConfig.elm and elm.json) then running elm-review init. Then you can copy paste what you had in your previous ReviewConfig into the new one.

In practice, you should be able to have a very similar configuration, but the following sections might make you change a few things.

Tests now included by default

If you were running elm-review with arguments, I recommend removing them and to see if that works out.

The tests/ directory is now included by default, so you might get errors from that. To ignore these errors for the moment, you can change the arguments to elm-review, or use Rule.ignoreErrorsForDirectories. I recommend having your tests reviewed after the migration phase.

Rule changes

Here are the changes for the review packages from jfmengels.


The NoDebug rule is split into NoDebug.Log and NoDebug.TodoOrToString. Just remove the former and add the latter two rules to have the same.


NoUnused.CustomTypeConstructors now takes an argument, which you can replace by [].

Notice that both NoUnused.Variables and NoUnused.CustomTypeConstructors can report new errors though, so you might need to fix the errors or to disable the rule temporarily.

There are now a lot of new rules that you can pick up from, so go check those out!