NEW Turn on some ESLint rules

[sabina-talipova]

Description

Turn on the following ESLint rules:

General rules:

• indent: Enforce consistent indentation. Link
• no-unused-vars: Disallow unused variables. Link
• no-dupe-keys: Disallow duplicate keys in object literals. Link
• no-multiple-empty-lines: Disallow multiple empty lines. Link
• no-unneeded-ternary: Disallow ternary operators when simpler alternatives exist. Link
• semi-style: Enforce location of semicolons. Link
• lines-between-class-members: Require or disallow an empty line between class members. Link
• max-classes-per-file: Enforce a maximum number of classes per file. Link
• no-param-reassign: Disallow reassigning function parameters. Link

JSX-a11y:

• jsx-a11y/href-no-hash: Probably was removed from API. Replaced with anchor-is-valid

Import rules:

• import/order: Enforce a convention in the order of require() / import statements. Link
• import/no-cycle: Ensures that there is no resolvable path back to this module via its dependencies. Link
• import/no-unresolved: Ensures an imported module can be resolved to a module on the local filesystem, as defined by standard Node require.resolve behavior. Link
• import/first: This rule reports any imports that come after non-import statements. Link

React lib rules:

• react/no-access-state-in-setstateLink
• react/jsx-fragments Enforce shorthand or standard form for React fragments. Link
• react/jsx-curly-brace-presence: Disallow unnecessary JSX expressions when literals alone are sufficient or enforce JSX expressions on literals in JSX children or attributes. Link
• react/jsx-no-useless-fragment: Disallow unnecessary fragments. Link
• react/no-unused-state: Disallow definitions of unused state. Link
• react/no-deprecated: Disallow usage of deprecated methods. Link
• react/prefer-stateless-function: Enforce stateless components to be written as a pure function. Link
• react/no-array-index-key: Disallow usage of Array index in keys. Link
• react/jsx-indent: Enforce JSX indentation. Link
• react/no-unused-prop-types: Disallow definitions of unused propTypes. Link

Should be reviewed and turned on in the future:

• import/prefer-default-export: In exporting files, this rule checks if there is default export or not. Link
• jsx-a11y/anchor-is-valid: The HTML a element, with a valid href attribute, is formally defined as representing a hyperlink. Link
• jsx-a11y/iframe-has-title: <iframe> elements must have a unique title property to indicate its content to the user. Link
• comma-dangle: Require or disallow trailing commas. Link
• arrow-parens: Require parentheses around arrow function arguments. Link
• prefer-destructuring: Require destructuring from arrays and/or objects. Link
• func-names: Require or disallow named function expressions. Link
• react/forbid-foreign-prop-types: Disallow using another component's propTypes. Link
• react/prop-types: Disallow missing props validation in a React component definition. Link
• no-restricted-globals Disallow specified global variables. Link
• jsx-a11y/control-has-associated-label: Enforce that a control (an interactive element) has a text label. Link
• jsx-a11y/click-events-have-key-events: Enforce onClick is accompanied by at least one of the following: onKeyUp, onKeyDown, onKeyPress. Link
• jsx-a11y/no-static-element-interactions: Static HTML elements do not have semantic meaning. Link
• react/destructuring-assignment: Enforce consistent usage of destructuring assignment of props, state, and context. Link
• react/button-has-type: Disallow usage of button elements without an explicit type attribute. Link
• react/sort-comp: Enforce component methods order. Link
• default-param-last: Enforce default parameters to be last. Link
• prefer-object-spread: Disallow using Object.assign with an object literal as the first argument and prefer the use of object spread instead. Link
• no-redeclare: Disallow variable redeclaration. Link
• no-else-return: Disallow else blocks after return statements in if statements. Link
• function-call-argument-newline: Enforce line breaks between arguments of a function call. Link
• react/jsx-wrap-multilines: Disallow missing parentheses around multiline JSX. Link
• prefer-promise-reject-errors: Require using Error objects as Promise rejection reasons. Link
• no-promise-executor-return: Disallow returning values from Promise executor functions. Link
• react/require-default-props: Enforce a defaultProps definition for every prop that is not a required prop. Link
• react/default-props-match-prop-types: Enforce all defaultProps have a corresponding non-required PropType. Link
• react/no-find-dom-node: Disallow usage of findDOMNode. SUPPRESSED FOR NOW. Link

Rules that is still remaining turned off:

• react/jsx-closing-tag-location: Enforce closing tag location for multiline JSX. Link
• react/jsx-tag-spacing: Enforce whitespace in and around the JSX opening and closing brackets. Link
• react/jsx-filename-extension: Disallow file extensions that may contain JSX. Link
• function-paren-newline: Enforce consistent line breaks inside function parentheses. Link
• object-curly-newline: Enforce consistent line breaks after opening and before closing braces. Link
• operator-linebreak: Enforce consistent linebreak style for operators. Link
• react/jsx-curly-newline: Enforce consistent linebreaks in curly braces in JSX attributes and expressions. Link
• react/jsx-one-expression-per-line: Require one JSX element per line. Link
• import/no-extraneous-dependencies: Forbid the import of external modules that are not declared in the package.json's dependencies, devDependencies, optionalDependencies, peerDependencies, or bundledDependencies. The closest parent package.json will be used. Link
• no-underscore-dangle: Disallow dangling underscores in identifiers. Link
• react/forbid-prop-types: Disallow certain propTypes. Link
• class-methods-use-this: Enforce that class methods utilize this. Link
• no-useless-escape: Disallow unnecessary escape characters. Link
• jsx-a11y/anchor-has-content: Enforce that anchors have content and that the content is accessible to screen readers. Accessible means that it is not hidden using the aria-hidden prop. Refer to the references to learn about why this is important. Link
• react/jsx-props-no-spreading: Disallow JSX prop spreading. Link
• react/no-unused-class-component-methods: Disallow declaring unused methods of component class. Link
• react/function-component-definition: Enforce a specific function type for function components. Link

Parent issue

• Revisit JS linting silverstripe-admin#1433

[emteknetnz]

Have left a general comment that applies to all PRs on the parent issue silverstripe/silverstripe-admin#1433 (comment)