ESLint/Typescript Dev Config Module

This is the module with configuration for ESlint and Typescript used in every module in CS.

tsconfig

This module ships two base TypeScript configurations - they differ only in type-checking strictness.

• tsconfig.strict.json (recommended):

The recommended base config for all new and newly-migrated packages. Aligns with TypeScript 6.x defaults.

{
  "extends": "@cksource-cs/eslint-config-cs-module/tsconfig.strict.json"
}

• tsconfig.common.json (legacy):

The original, non-strict base config. Use it only for packages that have not yet been migrated to the strict preset. New packages should not extend this config.

{
  "extends": "@cksource-cs/eslint-config-cs-module/tsconfig.common.json"
}

Migration to 6.x

Version 6.0 enforces a new eslint.config.js, meaning that the flat config is now the default configuration format for ESLint. .eslintrc is officially deprecated and it should not be used, as the support for it will be removed in the upcoming major ESLint version.

We highly recommend to use JS modules (*.mjs) for defining configs:

import { defineConfig, globalIgnores } from 'eslint/config';
import csConfig from '@cksource-cs/eslint-config-cs-module';

export default defineConfig(
    csConfig,
    globalIgnores( [
        '**/coverage',
        '**/dist',
        '**/dist-tests'
    ] )
);

NOTE! The newest version does not export anymore the /typescript sub path. All format rules are exposed via one entrypoint.

Notable linter changes

• The new rule @typescript-eslint/consistent-type-imports encourages to specify a type keyword on imports to indicate that the export exists only in the type system, not at runtime. This allows transpilers to drop imports without knowing the types of the dependencies. This rule only output a warn message as it influences a major code style change in all existing imports.

• Due to the underlying breaking changes that happened in the eslint, some rules has been removed and moved to the third-party plugins. Notable rule changes include:

  • max-len -> @stylistic/max-len
  • indent -> @stylistic/indent
  • no-multi-spaces -> @stylistic/no-multi-spaces
  • no-path-concat -> node/no-path-concat
  • no-new-require -> node/no-new-require

• This new major version also started to properly lint test files, so you can notice more linter errors.

• Directives - in case of browser-environment scripts: /* eslint-env browser */ -> /* global window */

Dependencies requirements

• eslint: "9.37.x"
• typescript: "5.9.x"

The migrations process should contain steps similar as previously.

Migration to 3.x

Version 3.0.0 introduces some lint rules that can require some manual fixes (everything based on comments during the code review process) and introduce config for Typescript > 4.

From version 3.0.0 this module requires specific dependencies:

• eslint: "8.6.0"
• eslint-import-resolver-node: "0.3.6"
• typescript: "5.4.5"

Note: it may be a situation when @types/node module is not updated. The best option update this module to 20.11.1.

So, the migrations process should contain similar steps:

1. Update devDependencies (eslint, Typescript, etc.) in project.
2. Update @cksource-cs/eslint-config-cs-module to version > 3.0.0
3. Run pnpm cli build [package_name] or npm run build
4. Run npm run lint:fix
5. Fix manually all lint problems.
6. Run npm run lint
7. Run all tests.
8. Fix tests.

Note: it can be a problem with ts-node in Mocha tests so recommendation is to remove ts-node and use approach with dist-tests. More information about migrating from Mocha to AVA can be found here: https://www.notion.so/Migrating-from-Mocha-to-AVA-48bd10bf8be141349c4a8d302d5f957d .

Updating linter rules

If you believe we need to change the ESLint rules, make sure to discuss it with the team first. Once you get the go-ahead, follow the steps below to update the package across the whole CS:

1. Update eslintrc.js as needed (with generic ESLint rules) and/or typescript.js (TS-specific rules only).
2. Bump the version of this module (eslint-config-cs-module) in package.json.
3. To estimate how much work will be needed to update the linter module in other packages, create local links and try applying auto-fixes:

csli link --min-version=3.0.0 eslint-config-cs-module && \
csli run lint:fix

4. If you're happy with the changes, proceed with a PR and release the new version of the ESLint module.
5. Once the PR has been merged, switch to master. Go to the CS repository root and run the following command to upgrade the ESLint module in all client packages. The command will also attempt to auto-fix any errors, similarly to what we did in step 2.

pnpm -r install --dev && \
csli run deps:check --command-options="-u,-f @cksource-cs/eslint-config-cs-module" && \
pnpm -r install --dev && \
csli run lint:fix

6. Apply manual fixes if needed, commit the changes to a feature branch and create a PR.