config.json

The config.json file describes the track's configuration. It contains vital information like the track's exercises and concepts.

Metadata

The following top-level properties contain general track metadata:

language: the track's language (e.g. "C#"). Its length must be <= 255. (required)
slug: the track's language as a lowercased, kebab-case string (e.g. "csharp"). Its length must be <= 255. (required)
active: a boolean value indicating if the track is active (i.e. students can join the track on the website) (required)
blurb: a short description of the language. Its length must be <= 400. (required)
version: the version of the config.json file (currently fixed to 3) (required)
online_editor: an object describing settings used for the online editor: (required)
- indent_style: either "space" or "tab" (required)
- indent_size: the indentation size as an integer (e.g. 4) (required)
- highlightjs_language: the language identifier for Highlight.js (see the full list of identifiers) (optional)
status: an object describing which v3 features should be enabled: (required)
- concept_exercises: a boolean value indicating if Concept Exercises have been built (required). When true the Exercism website interface changes to indicate that concept exercises are available for the track.
- test_runner: a boolean value indicating if a test runner has been implemented (required). When true we put submitted solutions through our testing infrastructure and show the results on the website. The website also allows students to initiate a test run from within the online editor.
- representer: a boolean value indicating if a representer has been implemented (required)
- analyzer: a boolean value indicating if an analyzer has been implemented (required)
files: The patterns for the locations of the files used in an exercise, relative to the exercise's directory. (optional)
- solution: stub implementation file(s) pattern (optional)
- test: test file(s) pattern (optional)
- example: example implementation file(s) pattern (optional)
- exemplar: exemplar implementation file(s) pattern (optional)
- editor: additional read-only editor file(s) patterns (optional)
test_runner: an object describing the track's test runner (if any): (required if status.test_runner is true)
- average_run_time: an integer number value for the number of seconds the test runner takes on average to run (e.g. 4) (required if status.test_runner is true)
approaches: an object with metadata on the track's approaches: (required if the track has any approaches)
- snippet_extension: a string value used for the snippet file's extension (e.g. rb) (required if the track has any approaches)

Files

This key is used to specify track-wide file locations. Rather than maintainers having to manually set the files key in the exercises' config.json files, configlet can automatically populate it using these track-wide patterns.

The file patterns defined in the files object support the following placeholders:

%{kebab_slug}: the kebab-case exercise slug (e.g. bit-manipulation)
%{snake_slug}: the snake_case exercise slug (e.g. bit_manipulation)
%{camel_slug}: the camelCase exercise slug (e.g. bitManipulation)
%{pascal_slug}: the PascalCase exercise slug (e.g. BitManipulation)

Support will be added to configlet to use these pattern to populate the files key in an exercise's .meta/config.json file.

Example

{
  "language": "C#",
  "slug": "csharp",
  "active": true,
  "status": {
    "concept_exercises": true,
    "test_runner": true,
    "representer": false,
    "analyzer": false
  },
  "blurb": "C# is a modern, object-oriented language with lots of great features, such as type-inference and async/await. The tooling is excellent, and there is extensive, well-written documentation.",
  "version": 3,
  "online_editor": {
    "indent_style": "space",
    "indent_size": 4,
    "highlightjs_language": "csharp"
  },
  "test_runner": {
    "average_run_time": 2
  },
  "files": {
    "solution": [
      "%{pascal_slug}.cs"
    ],
    "test": [
      "%{pascal_slug}Tests.cs"
    ],
    "example": [
      ".meta/Example.cs"
    ],
    "exemplar": [
      ".meta/Exemplar.cs"
    ]
  }
}

Exercises

The top-level exercises key is an object with three possible keys:

concept: this is an array listing the track's concept exercises
practice: this is an array listing the track's practice exercises
foregone: this is an array listing the slugs of exercises the track won't implement

Concept exercises

Each concept exercise is an entry in the exercises.concept array. Exercises are ordered on the website in the same order they are listed in this file, and should match the typical order in which they should be solved. The following fields make up a concept exercise:

uuid: a V4 UUID that uniquely identifies the exercise. The UUID must be unique both within the track as well as across all tracks, and must never change
slug: the exercise's slug, which is a lowercased, kebab-case string. The slug must be unique across all concept and practice exercise slugs within the track. Its length must be <= 255.
name: the exercise's name. Its length must be <= 255.
concepts: an array of concept slugs that are taught by this concept exercise
prerequisites: an array of concept slugs that must be unlocked before a student can start this exercise
status (optional): the exercise's status, which is one of "wip", "beta" "active", or "deprecated"; defaults to "active" if not specified
- wip: A work-in-progress exercise not ready for public consumption. Exercises with this tag will not be shown to students on the UI or be used for unlocking logic. They may appear for maintainers.
- beta: This signifies active exercises that are new and which we would like feedback on. We show a beta label on the site for these exercise, with a Call To Action of "Please give us feedback."
- active: The normal state of active exercises
- deprecated: Exercises that are no longer shown to students who have not started them (not usable at this stage). See Deprecated Exercises for more information.

Example

{
  "exercises": {
    "concept": [
      {
        "slug": "cars-assemble",
        "name": "Cars, Assemble!",
        "uuid": "93fbc7cf-3a7e-4450-ad22-e30129c36bb9",
        "concepts": [
          "if-statements",
          "numbers"
        ],
        "prerequisites": [
          "basics"
        ]
      },
      ...
    ]
  }
}

Example of work-in-progress

{
  "exercises": {
    "concept": [
      {
        "slug": "cars-assemble",
        "name": "Cars, Assemble!",
        "uuid": "93fbc7cf-3a7e-4450-ad22-e30129c36bb9",
        "concepts": [
          "if-statements",
          "numbers"
        ],
        "prerequisites": [
          "basics"
        ],
        "status": "wip"
      },
      ...
    ]
  }
}

Practice exercises

Each practice exercise is an entry in the exercises.practice array. The following fields make up a practice exercise:

uuid: a V4 UUID that uniquely identifies the exercise. The UUID must be unique both within the track as well as across all tracks, and must never change
slug: the exercise's slug, which is a lowercased, kebab-case string. The slug must be unique across all concept and practice exercise slugs within the track. Its length must be <= 255.
name: the exercise's name. Its length must be <= 255.
practices: an array of concept slugs that the exercise is helping students practice
prerequisites: an array of concept slugs that must be unlocked before a student can start the exercise
difficulty: a number indicating the difficulty of the exercise. The number must be in the range of 1 (easiest) to 10 (hardest). The website interprets the difficulty as follows:
- 1,2,3: easy
- 4,5,6,7: medium
- 8,9,10: hard
status (optional): the exercise's status, which is either "wip", "beta", "active" or "deprecated"; defaults to "active" if not specified
- wip: A work-in-progress exercise not ready for public consumption. Exercises with this tag will not be shown to students on the UI or be used for unlocking logic. They may appear for maintainers.
- beta: This signifies active exercises that are new and which we would like feedback on. We show a beta label on the site for these exercise, with a Call To Action of "Please give us feedback"
- active: The normal state of active exercises
- deprecated: Exercises that are no longer shown to students who have not started them (not usable at this stage).

The "Recommended Order" of the Practice Exercises on the website corresponds with the order of the exercises in the practice array.

Example

{
  "exercises": {
    "practice": [
      {
        "slug": "leap",
        "name": "Leap",
        "uuid": "8ba15933-29a2-49b1-a9ce-70474bad3007",
        "practices": [
          "if-statements",
          "numbers",
          "operator-precedence"
        ],
        "prerequisites": [
          "if-statements",
          "numbers"
        ],
        "difficulty": 1
      },
      ...
    ]
  }
}

Example of beta

{
  "exercises": {
    "practice": [
      {
        "slug": "leap",
        "name": "Leap",
        "uuid": "8ba15933-29a2-49b1-a9ce-70474bad3007",
        "practices": [
          "if-statements",
          "numbers",
          "operator-precedence"
        ],
        "prerequisites": [
          "if-statements",
          "numbers"
        ],
        "difficulty": 1,
        "status": "beta"
      },
      ...
    ]
  }
}

Foregone exercises

If a track knows that it doesn't want to implement an exercise defined in the Problem Specifications repo, the slug of that exercise can be added to the exercises.foregone key. configlet will ignore foregone exercises when outputting the track's unimplemented exercises.

Reasons for why an track might not want to implement an exercise could be:

The exercise can't reasonably be implemented by the language. As an example, the lens-person exercise requires the language to support lenses.
The exercise's topic doesn't fit the language. For example, for some high-level languages, a low-level bit-manipulation exercise might not make sense.

Example

{
  "exercises": {
    "foregone": [
      "lens-person"
    ]
  }
}

Concepts

Each concept is an entry in the top-level concepts array. The following fields make up a concept:

uuid: a V4 UUID that uniquely identifies the concept. The UUID must be unique both within the track as well as across all tracks, and must never change
slug: the concept's slug, which is a lowercased, kebab-case string. The slug must be unique across all concepts within the track. Its length must be <= 255.
name: the concept's name. Its length must be <= 255.
tags: Specify the conditions for when a submission is linked to an approach. (optional)
- all: An array of tags that must all be present on a submission (optional, unless any has no elements)
- any: An array of tags of which at least one must be present on a submission (optional, unless all has no elements)
- not: none of the tags must be present on a submission (optional)

Example

{
  "concepts": [
    {
      "uuid": "b9a421b2-c5ff-4213-bd6d-b886da31ea0d",
      "slug": "numbers",
      "name": "Numbers",
      "tags": {
        "all": [
          "concept:number"
        ]
      }
    }
  ]
}

Key features

The language's key features succinctly describe what the most important features of the language are. They are intended to promote the more interesting features of a language to potential students. Titles should strive to use as little technical jargon as possible, bearing in mind that students might not be familiar with what language-specific jargon means before learning that language.

The key features are specified in the top-level key_features field which is defined as an array of objects with the following fields:

title: a concise header for the key feature. Its length must be <= 25. Markdown is not supported.
content: a description of the key feature. Its length must be <= 100. Markdown is not supported.
icon: the icon to show for the feature. You can choose an icon that you think fits, regardless of its name. The following icons can be used:
- community
- concurrency
- cross-platform
- documentation
- dynamically-typed
- easy
- embeddable
- evolving
- expressive
- extensible
- fast
- fun
- functional
- garbage-collected
- general-purpose
- homoiconic
- immutable
- interactive
- interop
- multi-paradigm
- portable
- powerful
- productive
- safe
- scientific
- small
- stable
- statically-typed
- tooling
- web
- widely-used

You can check the visual appearance of these icons on the key feature icons section.

Exactly 6 key features must be specified.

Example

{
  "key_features": [
    {
      "title": "Fault-tolerant",
      "content": "Elixir runs on the Erlang VM, known for running low-latency, distributed and fault-tolerant systems.",
      "icon": "safe"
    },
    ...
  ],
}

Execution mode

execution_mode/compiled: code is compiled first before being executed
execution_mode/interpreted: code is interpreted directly

Platform

platform/windows: runs on Windows
platform/mac: runs on Mac
platform/linux: runs on Linux
platform/ios: runs on iOS
platform/android: runs on Android
platform/web: runs on Browser

Runtime

runtime/standalone_executable: runs as standalone executable
runtime/language_specific: runs on language-specific runtime
runtime/clr: runs on Common Language Runtime (.NET)
runtime/jvm: runs on JVM (Java)
runtime/beam: runs on BEAM (Erlang)
runtime/wasmtime: runs on Wasmtime (WebAssembly)

Used for

used_for/artificial_intelligence: Artificial Intelligence
used_for/backends: Backends
used_for/cross_platform_development: Cross-platform development
used_for/embedded_systems: Embedded systems
used_for/financial_systems: Financial systems
used_for/frontends: Frontends
used_for/games: Games
used_for/guis: GUIs
used_for/mobile: Mobile
used_for/robotics: Robotics
used_for/scientific_calculations: Scientific calculations
used_for/scripts: Scripts
used_for/web_development: Web development

Note that it is perfectly fine to include multiple tags from a single category.

Example

{
  "tags": [
    "paradigm/declarative",
    "paradigm/functional",
    "paradigm/object_oriented",
    "platform/linux",
    "platform/windows",
    "runtime/jvm"
  ]
}

Example

This is an example of what a valid config.json file can look like:

{
  "language": "C#",
  "slug": "csharp",
  "active": true,
  "status": {
    "concept_exercises": true,
    "test_runner": true,
    "representer": false,
    "analyzer": false
  },
  "blurb": "C# is a modern, object-oriented language with lots of great features, such as type-inference and async/await. The tooling is excellent, and there is extensive, well-written documentation.",
  "version": 3,
  "online_editor": {
    "indent_style": "space",
    "indent_size": 4,
    "highlightjs_language": "csharp"
  },
  "test_runner": {
    "average_run_time": 2
  },
  "files": {
    "solution": [
      "%{pascal_slug}.cs"
    ],
    "test": [
      "%{pascal_slug}Tests.cs"
    ],
    "example": [
      ".meta/Example.cs"
    ],
    "exemplar": [
      ".meta/Exemplar.cs"
    ]
  },
  "exercises": {
    "concept": [
      {
        "slug": "lucians-luscious-lasagna",
        "name": "Lucian's Luscious Lasagna",
        "uuid": "7d358894-4fbd-4c91-b49f-d68f1c5aa6bc",
        "concepts": [
          "basics"
        ],
        "prerequisites": []
      },
      {
        "slug": "cars-assemble",
        "name": "Cars, Assemble!",
        "uuid": "93fbc7cf-3a7e-4450-ad22-e30129c36bb9",
        "concepts": [
          "if-statements",
          "numbers"
        ],
        "prerequisites": [
          "basics"
        ],
        "status": "wip"
      }
    ],
    "practice": [
      {
        "slug": "hello-world",
        "name": "Hello, World!",
        "uuid": "6c88f46b-5acb-4fae-a6ec-b48ae3f8168f",
        "practices": [
          "strings"
        ],
        "prerequisites": [
          "basics"
        ],
        "difficulty": 1
      },
      {
        "slug": "leap",
        "name": "Leap",
        "uuid": "8ba15933-29a2-49b1-a9ce-70474bad3007",
        "practices": [
          "if-statements",
          "numbers",
          "operator-precedence"
        ],
        "prerequisites": [
          "if-statements",
          "numbers"
        ],
        "difficulty": 2,
        "status": "beta"
      }
    ]
  },
  "concepts": [
    {
      "uuid": "2eb4a463-355f-46ef-ac55-a75ec5afdf86",
      "slug": "basics",
      "name": "Basics"
    },
    {
      "uuid": "4466e33e-dcd2-4b1f-9d9d-2c4315bf5188",
      "slug": "if-statements",
      "name": "If Statements"
    },
    {
      "uuid": "b9a421b2-c5ff-4213-bd6d-b886da31ea0d",
      "slug": "numbers",
      "name": "Numbers"
    },
    {
      "uuid": "7a86561d-173b-45c0-a53c-1ffd7b9ff259",
      "slug": "strings",
      "name": "Strings"
    }
  ],
  "key_features": [
    {
      "title": "Modern",
      "content": "C# is a modern, fast-evolving language.",
      "icon": "expressive"
    },
    {
      "title": "Cross-platform",
      "content": "C# runs on almost any platform and chipset.",
      "icon": "cross-platform"
    },
    {
      "title": "Multi-paradigm",
      "content": "C# is primarily an object-oriented language, but also has lots of functional features.",
      "icon": "multi-paradigm"
    },
    {
      "title": "General purpose",
      "content": "C# can be used for a wide variety of workloads, like websites, console applications, and even games.",
      "icon": "general-purpose"
    },
    {
      "title": "Tooling",
      "content": "C# has excellent tooling, with linting and advanced refactoring options built-in.",
      "icon": "tooling"
    },
    {
      "title": "Documentation",
      "content": "Documentation is excellent and exhaustive, making it easy to get started with C#.",
      "icon": "documentation"
    }
  ],
  "tags": [
    "paradigm/declarative",
    "paradigm/functional",
    "paradigm/object_oriented",
    "platform/linux",
    "platform/windows",
    "runtime/jvm"
  ]
}

config.json

Metadata

Files

Example

Exercises

Concept exercises

Example

Example of work-in-progress

Practice exercises

Example

Example of beta

Foregone exercises

Example

Concepts

Example

Key features

Example

Tags

Paradigms

Typing

Execution mode

Platform

Runtime

Used for

Example

Language Tracks

#48in24 Challenge

Your Journey

Exercism Perks

Community Videos

Brief Introduction Series

Interviews & Stories

Discord

Forum

Getting started

Mentoring

Docs

Contributors

Donate

About Exercism

Our Impact

Insiders

SWAG

config.json

Metadata

Files

Example

Exercises

Concept exercises

Example

Example of work-in-progress

Practice exercises

Example

Example of beta

Foregone exercises

Example

Concepts

Example

Key features

Example

Tags

Paradigms

Typing

Execution mode

Platform

Runtime

Used for

Example