Tool to assist in managing Exercism language tracks.
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A tool for managing Exercism language track repositories.


Exercism makes certain assumptions about language tracks. The configlet lint command makes it simple to verify up-front that the changes to a track's configuration, as well as changes and additions to the exercises will play nicely with the website.

configlet lint checks for the following configuration issues:

  1. config.json contents that are invalid according to the specification.
  2. Inconsistencies between the lists of track slugs in config.json and the corresponding implementation files:
    • Slugs referenced in config.json that have no corresponding implementation.
    • Slugs referenced in config.json whose implementation is missing an example solution.
    • Implementations for slugs that are not referenced in config.json.
    • Implementations for slugs that have been declared as foregone in config.json.


Inspired by Go's gofmt tool, configlet's fmt command will consistently format a track's configuration files.

configlet fmt formats according to the following rules:

  1. The JSON files, config.json and maintainers.json will be indented by 2 spaces.
  2. In the config.json file:
    • Exercises will have their list of topics sorted alphabetically.
    • Topics names will be normalised to be lowercase and contain underscores in place of spaces.


The configlet generate command may be used to generate README's for all exercises on the track, as a whole or individually. The overall purpose of this command is to utilize common problem-specifications data in generating a template-based README for each exercise, while at the same time permitting overrides of this data on a track exercise basis.

Using this command for README generation allows for some conveniences:

  1. The use of a track specific README template file.
  2. The automatic inclusion of information from the problem-specifications repository.
  3. Allow overrides of that problem-specification data on a per-exercise basis.
  4. The ability to insert language specific exercise information ("hints") to an exercise README.
  5. Full customization of a README template per exercise (if necessary).

generate looks for specific files in the track root's config/ directory and in each exercise's .meta/ directory. It will then use these files, if present, and the problem-specifications data to generate an exercise's README.

Much of the utility of this command comes from the ability to locally override README templates and exercise information.

(When working with READMEs you may find a local renderer for GitHub Markdown helpful to preview your work before committing.)

The README Template

The template file used as the basis for README generation lives in a track root's config/ directory as config/exercise_readme.go.tmpl. This template file may be overridden for an exercise by placing the overriding template in the exercises .meta/readme.go.tmpl.

As configlet is written in the Go language this README template file is in the Go template format.

There are a number of template variable substitutions you may place in the template file:


This variable is sourced from an exercise's file in the problem-specifications repo. You may override this variable's contents for an exercise by adding a .meta/ file in that track exercise's directory.


The credits are a description of the source of an exercise with an optional hyperlink to that source. This information originates from the metadata.yml located in the exercise's problem-specifications entry. You may override this information for an exercise by adding a .meta/metadata.yml file in that track exercise's directory.


This variable is a readable version of the exercise's slug in title case. There are alternative formats of the name available. These formats may be useful if you need to reference the exercise name in regards to tooling.

Variable Contents
.Spec.Slug difference-of-squares
.Spec.Name Difference Of Squares
.Spec.MixedCaseName DifferenceOfSquares
.Spec.SnakeCaseName difference_of_squares


Language tracks will most likely have some unique information common to every exercise in the track (testing, environment configuration, etc...). This may be placed in a track's config/ file the contents of which will then be available in this template variable.


Exercises may have information specific to that exercise's implementation in the track language (for example, the introduction of a specific language concept). In this case placing a .meta/ in that track exercise's directory will make those contents available in this template variable.


The track configuration file can be hard to review, especially the new structure being used for nextercism. The tree command can help with the process of setting up your configuration file for nextercism. It will:

  1. Display the core track exercises and unlocked exercises as a tree.
  2. List out the bonus exercises separately.
  3. Issue warnings if expected elements from the nextercism-style configuration are missing.
  4. Optionally show the difficulty of the exercises via the --with-difficulty option.


The configlet upgrade command downloads and installs the latest released version of configlet. Running the upgrade command on an already up-to-date version of configlet will exit with no change to the system. The version command configlet version -l can be used to check for the latest available version.


Exercises in each track config.json file must have a UUID. You may request a randomly generated exercise UUID from configlet using:

$ configlet uuid


$ configlet [command] <path/to/track>

If you have installed the configlet binary and are at the root of an exercism language track, then you can run the following:

$ configlet [command] .