[#IP-86] tslint to eslint migration

[michaeldisaro]

List of Changes

• Deleted tslint.json file
• Removed tslint packages from package.json
• Created .eslintignore ignore file
• Created .eslintrc.js configuration
• Added some lint exclusions to .eslintrc.js to avoid a deep refactoring of working code
• Changed tslint's "rule disabling" comments with eslint closest ones.

Motivation and Context

We want to migrate to eslint because tslint is deprecated.

How Has This Been Tested?

It has been tested by performing:

• yarn install --frozen-lockfile
• yarn build
• yarn lint
• yarn test

Types of changes

• Chore (nothing changes by a user perspective)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[pagopa-github-bot]

	Warnings
⚠️	Please include a Pivotal story at the beginning of the PR title (see below).
⚠️	This PR changes a total of 1820 LOCs, that is more than a reasonable size of 250. Consider splitting the pull request into smaller ones.

Example of PR titles that include pivotal stories:

• single story: [#123456] my PR title
• multiple stories: [#123456,#123457,#123458] my PR title

New dependencies added: @pagopa/eslint-config and eslint-plugin-prettier.

@pagopa/eslint-config

Author: Unknown

Description: This package provide the following ESLint custom rules for Typescript projects.

Homepage: https://github.com/pagopa/eslint-rules#readme

Created	3 months ago
Last Updated	about 15 hours ago
License	MIT
Maintainers	5
Releases	6
Direct Dependencies	@typescript-eslint/eslint-plugin, @typescript-eslint/eslint-plugin-tslint, @typescript-eslint/parser, eslint, eslint-config-prettier, eslint-plugin-extra-rules, eslint-plugin-fp, eslint-plugin-functional, eslint-plugin-import, eslint-plugin-jsdoc, eslint-plugin-no-credentials, eslint-plugin-prefer-arrow, eslint-plugin-prettier, eslint-plugin-react, eslint-plugin-sonarjs and prettier

README

PagoPA ESLint config

This package provide the following ESLint custom rules for Typescript projects.

• recommendend
• react
• strong

This repository replace italia-tslint-rules after TSLint deprecation.

The following TSLint rules (included inside italia-tslint-rules) are not supported for eslint at the moment and are missing in this package:

bool-param-default
max-union-size
no-accessor-field-mismatch
no-array-delete // Mitigated by no-delete
no-case-with-or
no-dead-store
no-duplicate-in-composite
no-empty-array
no-extra-semicolon // Mitigated by prettier
no-empty-destructuring // Mititgated by no-empty-pattern
no-gratuitous-expressions
no-hardcoded-credentials
no-ignored-initial-value // Mitigated by no-param-reassign, no-let
no-in-misuse
no-inferred-empty-object-type
no-invalid-await // Mititgated by await-thenable
no-invariant-return
no-misleading-array-reverse // Mitigated by immutable-data
no-misspelled-operator // Mitigated by prettier
no-nested-switch
no-nested-template-literals
no-statements-same-line // Mitigated by prettier
no-try-promise
no-tslint-disable-all
no-unconditional-jump
no-undefined-argument
no-unenclosed-multiline-block // Mitigated by prettier
no-unthrown-error
no-unused-array // Mitigated by no-unused-vars
no-useless-increment
no-useless-intersection
prefer-promise-shorthand
promise-must-complete
use-primitive-type

This list has been produced following these steps:

1. Follow TSLint to ESLint migration guide on the project io-backend
2. Running npx tslint-to-eslint-config that produces a list of TSLint rules not available for ESLint (77 rules at the moment)
3. Manually check each one for an alternative ESLint rules/plugins
4. Verify each alternative ESLint rule/plugin on a testing file

Usage

Installation and Configuration

To use this package install as devDependecy inside any typescript project with

yarn install -D @pagopa/eslint-config

Create on the project an .eslintrc.js file with the following content

module.exports = {
  "extends": [
    "@pagopa/eslint-config/strong",
  ],
  "rules": {
    // Any project level custom rule
  }
}

Add inside the package.json file a lint and optionally a lint-autofix script as:

"scripts": {
  "lint": "eslint . -c .eslintrc.js --ext .ts,.tsx",
  "lint-autofix": "eslint . -c .eslintrc.js --ext .ts,.tsx --fix",
  ...
}

Migration from TSLint

Remove from the package.json every tslint reference:

• tslint
• italia-tslint-rules

Replace all the // tslint:disable-next-line with the proper // eslint-disable-next-line comment. If are present some // tslint:disable replace it with /* eslint-disable */ at the top of the file.

If you need to disable ESLint for some files create .eslintignore file with the list of folders or files that must be excluded from lint process. Copy the exclusion from tslint.json linterOptions.exclude

Delete all tslint related files (es. tslint.json).

Run yarn lint-autofix to refactorize the code automatically with all the auto-fixable ESLint rules.

eslint-plugin-prettier

Author: Teddy Katz

Description: Runs prettier as an eslint rule

Homepage: https://github.com/prettier/eslint-plugin-prettier#readme

Created	about 4 years ago
Last Updated	about 6 hours ago
License	MIT
Maintainers	4
Releases	26
Direct Dependencies	prettier-linter-helpers
Keywords	eslint, eslintplugin, eslint-plugin and prettier

README

eslint-plugin-prettier

Runs Prettier as an ESLint rule and reports differences as individual ESLint issues.

If your desired formatting does not match Prettier’s output, you should use a different tool such as prettier-eslint instead.

Please read Integrating with linters before installing.

Sample

error: Insert `,` (prettier/prettier) at pkg/commons-atom/ActiveEditorRegistry.js:22:25:
  20 | import {
  21 |   observeActiveEditorsDebounced,
> 22 |   editorChangesDebounced
     |                         ^
  23 | } from './debounced';;
  24 |
  25 | import {observableFromSubscribeFunction} from '../commons-node/event';


error: Delete `;` (prettier/prettier) at pkg/commons-atom/ActiveEditorRegistry.js:23:21:
  21 |   observeActiveEditorsDebounced,
  22 |   editorChangesDebounced
> 23 | } from './debounced';;
     |                     ^
  24 |
  25 | import {observableFromSubscribeFunction} from '../commons-node/event';
  26 | import {cacheWhileSubscribed} from '../commons-node/observable';


2 errors found.

./node_modules/.bin/eslint --format codeframe pkg/commons-atom/ActiveEditorRegistry.js (code from nuclide).

Installation

npm install --save-dev eslint-plugin-prettier
npm install --save-dev --save-exact prettier

eslint-plugin-prettier does not install Prettier or ESLint for you. You must install these yourself.

Then, in your .eslintrc.json:

{
  "plugins": ["prettier"],
  "rules": {
    "prettier/prettier": "error"
  }
}

Recommended Configuration

This plugin works best if you disable all other ESLint rules relating to code formatting, and only enable rules that detect potential bugs. (If another active ESLint rule disagrees with prettier about how code should be formatted, it will be impossible to avoid lint errors.) You can use eslint-config-prettier to disable all formatting-related ESLint rules.

This plugin ships with a plugin:prettier/recommended config that sets up both the plugin and eslint-config-prettier in one go.

1. In addition to the above installation instructions, install eslint-config-prettier:

   npm install --save-dev eslint-config-prettier

2. Then you need to add plugin:prettier/recommended as the last extension in your .eslintrc.json:

   {
     "extends": ["plugin:prettier/recommended"]
   }

   You can then set Prettier's own options inside a .prettierrc file.

Exactly what does plugin:prettier/recommended do? Well, this is what it expands to:

{
  "extends": ["prettier"],
  "plugins": ["prettier"],
  "rules": {
    "prettier/prettier": "error",
    "arrow-body-style": "off",
    "prefer-arrow-callback": "off"
  }
}

• "extends": ["prettier"] enables the config from eslint-config-prettier, which turns off some ESLint rules that conflict with Prettier.
• "plugins": ["prettier"] registers this plugin.
• "prettier/prettier": "error" turns on the rule provided by this plugin, which runs Prettier from within ESLint.
• "arrow-body-style": "off" and "prefer-arrow-callback": "off" turns off two ESLint core rules that unfortunately are problematic with this plugin – see the next section.

arrow-body-style and prefer-arrow-callback issue

If you use arrow-body-style or prefer-arrow-callback together with the prettier/prettier rule from this plugin, you can in some cases end up with invalid code due to a bug in ESLint’s autofix – see issue #65.

For this reason, it’s recommended to turn off these rules. The plugin:prettier/recommended config does that for you.

You can still use these rules together with this plugin if you want, because the bug does not occur all the time. But if you do, you need to keep in mind that you might end up with invalid code, where you manually have to insert a missing closing parenthesis to get going again.

If you’re fixing large of amounts of previously unformatted code, consider temporarily disabling the prettier/prettier rule and running eslint --fix and prettier --write separately.

Options

Note: While it is possible to pass options to Prettier via your ESLint configuration file, it is not recommended because editor extensions such as prettier-atom and prettier-vscode will read .prettierrc, but won't read settings from ESLint, which can lead to an inconsistent experience.

• The first option:

  • An object representing options that will be passed into prettier. Example:

    "prettier/prettier": ["error", {"singleQuote": true, "parser": "flow"}]

    NB: This option will merge and override any config set with .prettierrc files

• The second option:

  • An object with the following options

    • usePrettierrc: Enables loading of the Prettier configuration file, (default: true). May be useful if you are using multiple tools that conflict with each other, or do not wish to mix your ESLint settings with your Prettier configuration.

      "prettier/prettier": ["error", {}, {
        "usePrettierrc": false
      }]

    • fileInfoOptions: Options that are passed to prettier.getFileInfo to decide whether a file needs to be formatted. Can be used for example to opt-out from ignoring files located in node_modules directories.

      "prettier/prettier": ["error", {}, {
        "fileInfoOptions": {
          "withNodeModules": true
        }
      }]

• The rule is autofixable -- if you run eslint with the --fix flag, your code will be formatted according to prettier style.

---

Contributing

See CONTRIBUTING.md

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[michaeldisaro]

@balanza i fixed yarn.lock and merged your commit

[balanza]

@michaeldisaro please review changes in 5ce9618, I tried to explain more in the review.