eslint-plugin-dci-lint

This is a TypeScript ESLint plugin that helps you adhere to DCI conventions. For more information about DCI (Data, Context and Interaction), read this introduction.

Installation

Note: Version 0.9+ of the plugin uses ESLint 9 and ESM.

Use npm or pnpm to install the plugin and its required packages:

npm i -D eslint @eslint/js typescript typescript-eslint eslint-plugin-dci-lint

pnpm i -D eslint @eslint/js typescript typescript-eslint eslint-plugin-dci-lint

Configuration

Add the dci-lint plugin and the typescript parser to your eslint.config.js configuration file:

import eslint from "@eslint/js";
import tseslint from "typescript-eslint";
import dciLint from "eslint-plugin-dci-lint";

export default tseslint.config(
  eslint.configs.recommended,
  tseslint.configs.recommended,
  dciLint.configs.recommended,
  {
    rules: {
      //"dci-lint/literal-role-contracts": "off"
    },
  }
);

Linting the code

In the project directory, you can run ESLint with npx eslint . but while coding it's best to use it with a code editor. This VS Code extension gives you linting as you type (or search for ESLint in the extensions panel).

How to use / DCI Tutorial

A comprehensive tutorial series is available at https://blog.encodeart.dev/dci-tutorial-for-typescript-part-1.

Supported Rules

Required

These rules should not be turned off. Let me know if you have a good reason to do so.

Rule	Usage
dci-lint/atomic-role-binding	All RoleMethods must be bound (assigned) in the same function.
dci-lint/grouped-rolemethods	RoleMethods must be grouped together, without unrelated code between them.
dci-lint/no-this-in-context	Disallows this in Contexts.
dci-lint/private-role-access	Private RoleMethods and Role contracts can only be accessed within their own Roles.

Optional

These rules are optional but are set to warn as default.

Rule	Usage
dci-lint/literal-role-contracts	Role contracts should be defined as an object type, primitive type or an array (in bracket syntax).

Turning this rule off can undermine the readability of the Context by requiring knowledge about types defined elsewhere in the code, but it can be convenient if you're working with a standardized API like the W3C web standards.

Additionally, a few other standard types are allowed as non-literal types for Roles:

Iterable | Array | Map | Set | Readonly | NonNullable | Awaited

Disabled

These rules are optional and are disabled as default.

Rule	Usage
dci-lint/immutable-roles	Enforces all Roles to be const.
dci-lint/sorted-rolemethods	RoleMethods must be placed in alphabetical order.

More information

Please dive into fulloo.info and its extensive documentation. The trygve manual on that site is a worthwhile read for any programmer regardless of skill level.

VS Code snippets

For VS Code, there are also some useful snippets in the typescript.json file in this repo. To use it:

• Go to File > Preferences > Configure User Snippets
• Choose TypeScript in the list
• Paste the contents of the file there.

You can now use the keywords "context", "role" and "rm" in .ts files to quickly generate Contexts, Roles and RoleMethods.

Test example

Paste this code in a .ts file to test if the plugin works with the linter. An error, "Accessing Role contract outside its own RoleMethods" should appear.

/**
 * @DCI-context
 */
export function Test() {
  const FirstRole = { name: "Test" };

  function FirstRole_method() {
    return FirstRole.name;
  }

  console.log(FirstRole.name); // Accessing Role contract outside its own RoleMethods.
  return FirstRole_method();
}

Comments, ideas, issues

Are best expressed as a Github issue here!

Thanks

Thanks to the Typescript ESLint project for making this possible at all!

And as always, a big thanks to the late Trygve Reenskaug for inventing DCI, and James Coplien for continously furthering it over the years.