Use ESLint

[tukusejssirs]

ESLint is used to define some style rules, as well as it checks some common code mistakes. ESLint statically analyses the code to quickly find problems.

[MRIIOT]

This is a dev behavior change.
Push .eslintrc file once created.

[tukusejssirs]

This is my current ESLint config. I don’t want to force anyone my preferences, therefore @bburns, we could discuss individual configs and decide on what will be used in l99 repo. Also, I prefer using JSON file (.eslintrc.json) instead of JS, however, I don’t mind using a JS file instead. I commented on som config in this issue. Also note that until we use Nx, we need to remove all config that mentions nx or nrwl.

.eslintrc.json

{
   "extends": [
      "eslint:recommended",
      "plugin:import/recommended"
   ],
   "overrides": [
      {
         "files": [
            "*.ts",
            "*.tsx",
            "*.js",
            "*.jsx",
            "*.cjs",
            "*.mjs"
         ],
         "rules": {
            "@nrwl/nx/enforce-module-boundaries": [
               "error",
               {
                  "allow": [],
                  "depConstraints": [
                     {
                        "onlyDependOnLibsWithTags": [
                           "*"
                        ],
                        "sourceTag": "*"
                     }
                  ],
                  "enforceBuildableLibDependency": true
               }
            ]
         }
      },
      {
         "extends": [
            "plugin:@typescript-eslint/eslint-recommended",
            "plugin:@typescript-eslint/recommended"
         ],
         "files": [
            "*.ts",
            "*.tsx"
         ],
         "rules": {
            "@typescript-eslint/array-type": ["error", {"default": "array"}],
            "@typescript-eslint/class-literal-property-style": ["error", "getters"],
            "@typescript-eslint/explicit-function-return-type": "error",
            "@typescript-eslint/explicit-member-accessibility": ["error", {"accessibility": "no-public"}],
            "@typescript-eslint/explicit-module-boundary-types": "error",
            "@typescript-eslint/indent": [
               "error",
               "tab",
               {
                  "ArrayExpression": 1,
                  "FunctionDeclaration": {
                     "parameters": "first"
                  },
                  "ImportDeclaration": 1,
                  "ObjectExpression": 1,
                  "SwitchCase": 1,
                  "VariableDeclarator": "first",
                  "flatTernaryExpressions": false,
                  "ignoredNodes": [
                     "FunctionExpression > .params[decorators.length > 0]",
                     "FunctionExpression > .params > :matches(Decorator, :not(:first-child))",
                     "ClassBody.body > PropertyDefinition[decorators.length > 0] > .key"
                  ]
               }
            ],
            "@typescript-eslint/interface-name-prefix": "off",
            // TODO: Consider either raising `@typescript-eslint/no-confusing-non-null-assertion` to `error` or removing the rule.
            "@typescript-eslint/no-confusing-non-null-assertion": "warn",
            // TODO: Consider changing `@typescript-eslint/no-explicit-any` to `error`.
            "@typescript-eslint/no-explicit-any": "off",
            "@typescript-eslint/no-extra-parens": [
               "error"
            ],
            "@typescript-eslint/no-floating-promises": [
               "error"
            ],
            "@typescript-eslint/no-non-null-assertion": "error",
            // TODO: Configure this config.
            // "@typescript-eslint/no-unused-vars": [
            //    "error",
            //    {
            //       "argsIgnorePattern": "^_",
            //       "ignoreRestSiblings": true
            //    }
            // ],
            "@typescript-eslint/no-use-before-define": "error",
            "@typescript-eslint/parameter-properties": "off",
            "@typescript-eslint/prefer-includes": "error",
            "@typescript-eslint/prefer-optional-chain": "error",
            "@typescript-eslint/prefer-readonly": "error",
            "@typescript-eslint/prefer-regexp-exec": "error",
            "@typescript-eslint/require-array-sort-compare": ["error", {"ignoreStringArrays": true}],
            "@typescript-eslint/return-await": ["error", "always"],
            "no-extra-parens": "off",
            "no-return-await": "off",
            "no-use-before-define": "off"
         }
      },
      {
         "files": [
            "*.js",
            "*.jsx"
         ],
         "rules": {
            "no-extra-parens": ["error"],
            "no-return-await": 2,
            "no-use-before-define": "error"
         }
      }
   ],
   "parser": "@typescript-eslint/parser",
   "parserOptions": {
      "ecmaVersion": 2020,
      "project": "tsconfig.base.json",
      "sourceType": "module"
   },
   "plugins": [
      "@nrwl/nx",
      "@typescript-eslint",
      "@typescript-eslint/eslint-plugin",
      "eslint-plugin-tsdoc",
      // TODO: Consider using these plugins.
      // "simple-import-sort",
      // "import",
      // "jest",
      "sort-keys-custom-order",
      "unicorn"
   ],
   "root": true,
   "rules": {
      "array-bracket-spacing": [
         "error",
         "never"
      ],
      "arrow-body-style": [
         "error",
         "as-needed"
      ],
      "arrow-parens": [
         "error",
         "as-needed"
      ],
      "comma-dangle": [
         "error",
         "never"
      ],
      "comma-spacing": [
         "error",
         {
            "before": false,
            "after": true
         }
      ],
      "computed-property-spacing": [
         "error",
         "never"
      ],
      "curly": "error",
      "for-direction": "error",
      "import/first": "error",
      "import/named": "error",
      "import/newline-after-import": "error",
      "import/no-duplicates": "error",
      "import/no-unresolved": "off",
      "import/no-unused-modules": "error",
      "import/order": [
         "error",
         {
            "alphabetize": {
               "caseInsensitive": true,
               "order": "asc"
            },
            "groups": [
               "builtin",
               "external",
               [
                  "internal",
                  "parent",
                  "sibling",
                  "index"
               ],
               [
                  "object",
                  "type"
               ]
            ],
            "newlines-between": "always"
         }
      ],
      // TODO: Why did I turn `indent` rule off for JS files? If needed look at the following config from old romcal ESLint config.
      // indent: [
      //    'error',
      //    'tab',
      //    {
      //       SwitchCase: 1,
      //       VariableDeclarator: 'first',
      //       FunctionDeclaration: {parameters: 'first'},
      //       ArrayExpression: 1,
      //       ObjectExpression: 1,
      //       ImportDeclaration: 1,
      //       flatTernaryExpressions: false
      //    }
      // ],
      "indent": "off",
      "key-spacing": [
         "error",
         {
            "singleLine": {
               "afterColon": true,
               "beforeColon": false
            },
            "multiLine": {
               "afterColon": true,
               "beforeColon": false
            }
         }
      ],
      "keyword-spacing": [
         "error",
         {
            "after": true,
            "before": true
         }
      ],
      "linebreak-style": ["error", "unix"],
      // TODO: One [this discussion](https://github.com/eslint/eslint/discussions/16142) has a solution, I’d like to enforce newlines before and after multi-line class members (of course, not at the beginning and at the end of the class).
      // "lines-between-class-members": ["error", "always"],
      "max-len": [
         "error",
         {
            "code": 175,
            "ignoreComments": true,
            "ignoreRegExpLiterals": true,
            "ignoreStrings": true,
            "ignoreTemplateLiterals": true,
            "ignoreTrailingComments": true,
            "ignoreUrls": true,
            "tabWidth": 2
         }
      ],
      // TODO: Consider setting `new-cap` to `error`.
      // 'new-cap': 'error',
      "new-cap": "off",
      "no-case-declarations": "off",
      "no-fallthrough": "off",
      "no-lonely-if": "error",
      "no-mixed-spaces-and-tabs": "error",
      "no-new-wrappers": "error",
      "no-multiple-empty-lines": [
         "error",
         {
            "max": 1,
            "maxBOF": 0,
            "maxEOF": 0
         }
      ],
      "no-tabs": [
         "error",
         {
            "allowIndentationTabs": true
         }
      ],
      "no-trailing-spaces": "error",
      // TODO: Consider making `no-unused-vars` to error out, which is enabled by `eslint:recommend`, thus simply remove this rule.
      "no-unused-vars": "off",
      "no-useless-concat": "error",
      "no-var": "error",
      "object-curly-spacing": [
         "error",
         "never"
      ],
      "object-property-newline": [
         "error",
         {
            "allowAllPropertiesOnSameLine": true
         }
      ],
      "padded-blocks": [
         "error",
         "never"
      ],
      "prefer-template": "error",
      "quote-props": [
         "error",
         "as-needed"
      ],
      "quotes": [
         "error",
         "single",
         {
            "allowTemplateLiterals": true,
            "avoidEscape": true
         }
      ],
      "semi": [
         "error",
         "never"
      ],
      "semi-spacing": [
         "error",
         {
            "before": false,
            "after": true
         }
      ],
      "sort-imports": [
         "error",
         {
            "allowSeparatedGroups": true,
            "ignoreCase": true,
            "ignoreDeclarationSort": true,
            "ignoreMemberSort": false,
            "memberSyntaxSortOrder": [
               "none",
               "all",
               "multiple",
               "single"
            ]
         }
      ],
      "sort-keys-custom-order/object-keys": "error",
      "sort-keys-custom-order/type-keys": "error",
      "sort-vars": [
         "error",
         {
            "ignoreCase": true
         }
      ],
      "space-before-blocks": "error",
      "spaced-comment": [
         "error",
         "always"
      ],
      "space-infix-ops": "error",
      "switch-colon-spacing": [
         "error",
         {
            "before": false,
            "after": true
         }
      ],
      "template-curly-spacing": ["error", "never"],
      "tsdoc/syntax": "warn",
      "unicorn/better-regex": "error",
      "unicorn/catch-error-name": [
         "error",
         {
            "name": "e"
         }
      ],
      "unicorn/consistent-destructuring": "error",
      "unicorn/custom-error-definition": "error",
      "unicorn/empty-brace-spaces": "error",
      "unicorn/error-message": "error",
      "unicorn/prefer-module": "error",
      "unicorn/prefer-node-protocol": "error",
      "wrap-regex": "off"
   }
}