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elm-review CLI

Run elm-review from Node.js.

elm-review reporter output


# Save it to your package.json, if you use npm in your project.
# This is the recommended way.
npm install elm-review --save-dev

# Install globally. This is not recommended.
npm install -g elm-review

See below if you want to try it out without installing it.


# Print the help
elm-review --help

# Review your project

# Create an empty review configuration
elm-review init

# Create a new project containing elm-review rules
# aimed at being published on the Elm package registry
elm-review new-package

# Create an empty new rule to get started.
# Very helpful for projects created with new-package
elm-review new-rule

Try it out

You can try elm-review out without setting up anything!

First of all, if you have node installed, it comes with npx, which lets you run elm-review without installing it by prepending the command by npx, like npx elm-review. It is a bit slower and requires Internet access, but it's useful to try it out.

You can also run a configuration you found on GitHub, using the --template flag. Even if you already have a configuration, you can use this to try out the rules from a new package before adding them to your configuration. For instance, if you want to find and remove the dead code in your project, you can use the example configuration from the jfmengels/elm-review-unused package.

npx elm-review --template jfmengels/elm-review-unused/example

# You can even use the configuration to fix all the errors that can be auto-fixed.
npx elm-review --template jfmengels/elm-review-unused/example --fix-all

If you are happy with the configuration, you can base your own configuration off of it, and then edit it:

npx elm-review init --template jfmengels/elm-review-unused/example

I highly recommend reading this section on when to enable rules in your configuration though.

You can use the same mechanics to try out a single rule before adding the dependency to your existing configuration and adding it to your configuration.

npx elm-review --template jfmengels/elm-review-unused/example --rules NoUnused.Variables


elm-review is configured through a review/ folder in your project. It is a self-contained Elm project where you can specify your dependencies, and write, import, and configure review rules.

Rules are configured in the review/ReviewConfig.elm file:

module ReviewConfig exposing (config)

import Review.Rule exposing (Rule)
import Third.Party.Rule
import My.Own.Custom.rule
import Another.Rule

config : List Rule
config =
    [ Third.Party.Rule.rule
    , My.Own.Custom.rule
    , Another.Rule.rule { ruleOptions = [] }

Get started

You can get started with an empty configuration by running the elm-review init command with the command line tool installed, which will add a review folder to your project.

You can also use an existing configuration using elm-review init --template <some configuration>. I created some configurations that I believe can be good starting points.

# Start with an empty configuration
elm-review init

# Starter configuration for an Elm application
elm-review init --template jfmengels/elm-review-config/application

# Starter configuration for an Elm package
elm-review init --template jfmengels/elm-review-config/package

Once you have set up an initial configuration, you can add new rules. As elm-review does not come with built-in rules, you can look for packages with rules on the Elm package registry by searching for packages named elm-review-.

Once you've found a package that you like, you can install it with the elm install command, just like any other Elm project dependency.

cd review/ # Go inside your review configuration directory
elm install authorName/packageName
# then update your `review/src/ReviewConfig.elm` to add the rule
# as explained in the package's documentation

Before you start adding rules or an unfamiliar existing configuration, I suggest reading the rest of this document, especially the section on when to enable a rule.

Run a review

Once you're done configuring, run elm-review to analyze your project.

You can also run elm-review --fix. The CLI will present you fixes for the errors that offer an automatic fix, which you can then accept or not. When there are no more fixable errors left, elm-review will report the remaining errors as if it was called without --fix. Fixed errors will be reformatted using elm-format.

Run elm-review --help for more information on the available flags.

elm-review # Analyze your project
elm-review --fix # Analyze your project and potentially proposes automatic fixes
elm-review --help # for more information and the available flags

Which parts of the project will be analyzed?

elm-review targets a project, and therefore requires an elm.json. By default, it will review all the Elm files of the project and of the tests.

  • For packages: all the Elm files in src/ and tests/
  • For applications: all the Elm files in tests/ and in the project's elm.json's source-directories

If you wish to, you can list the directories you wish to have reviewed, so as to review additional directories or to remove ignore some of directories, by adding them as arguments to the command line.

# Review `src/` if project is a package, or the "source-directories" otherwise, along with `tests/`
# Review only the Elm files in the `src/Dashboard/`
elm-review src/Dashboard/
# Review all the Elm files in the src/, tests/ and review/ directories
elm-review src/ tests/ review/
# Review a specific file
elm-review src/Dashboard.elm

The recommended way to use elm-review is without arguments. It is best not to "remove" directories from the project, because some rules expect to have access to all the files in order to make the best analysis. If some data is missing, they may make incorrect reports. If you wish to ignore some files, it is best to handle that in the implementation and/or configuration of your rules.

If you add files that are not part of the project, you may run into different problems, such as conflicting module names (two Main.elm files), relying on different dependencies, etc. It is best to run elm-review once for each project, and depending on your needs, with different configurations (using the --config flag).

Exit status

If any rule from your configuration reports an error in one of the analyzed files, the process will exit with status 1. Otherwise, it will exit with status 0.

If the process fails for any other reason (crash, misconfiguration, ...), it will exit with status 1.

Why is there a need for a review/ directory?

When the CLI looks at your configuration, it is in practice compiling an application using the configuration in your project, then running that application to analyze your project.

The CLI need at least two pieces of information from your configuration:

  • An elm.json file to know the external packages your configuration depends upon (like the ones that contain the rules you enabled), and the Elm version of your project
  • A ReviewConfig.elm file that sets the rules to enforce for your project

Your custom rules, unless you want to share them in the Elm package registry, should be in the review/ directory too, so as not to pollute your project's dependencies. If they are in here, we need to include these custom rules and their dependencies in the application files.

Tooling integration

If you are interested in using elm-review inside a different environment than a terminal (like editors, CI, other Elm tools, ...), check out the documentation for tooling integration.


Thanks to @MartinSStewart for working on reducing the file cache size (and therefore speeding up the whole execution).