.eslintrc.yml

env:
  node: true
  es6: true
  browser: true
  jest: true

parser: babel-eslint

parserOptions:
  ecmaFeatures:
    jsx: true

plugins:
  - eslint-plugin-flowtype
  - eslint-plugin-jest
  - eslint-plugin-ramda
  - eslint-plugin-react
  - eslint-plugin-react-redux
  - eslint-plugin-redux-saga

extends:
  - eslint:recommended
  - plugin:flowtype/recommended
  - plugin:import/errors
  - plugin:import/warnings
  - plugin:prettier/recommended
  - plugin:ramda/recommended
  - plugin:react/recommended
  - plugin:redux-saga/recommended

settings:
  react:
    version: "16.2.0"

rules:
  no-console: warn
  import/namespace: [2, { allowComputed: true }]
  no-unused-vars: ["error", { "ignoreRestSiblings": true }]
  comma-dangle: ["error", "always-multiline"]

  # marks Flow type identifiers as defined
  flowtype/define-flow-type: error
  # marks Flow type alias declarations as used
  flowtype/use-flow-type: error
  # must use verbose `Array` type syntax
  flowtype/array-style-complex-type: error
  flowtype/array-style-simple-type: error
  # avoid being sorted by `import-sort`
  flowtype/newline-after-flow-annotation: error
  # no duplicate keys in object
  flowtype/no-dupe-keys: error
  # disallow existential type `*`
  flowtype/no-existential-type: error
  # use `string` but not `String`
  flowtype/no-primitive-constructor-types: error
  # no unused flow expression
  flowtype/no-unused-expressions:
    - error
    - allowTaggedTemplates: true
  # disallow `Function` type
  flowtype/no-weak-types:
    - error
    - any: false
      Object: false
  # must use `,` for object separator
  flowtype/object-type-delimiter: error
  # object must have exact type `{||}`
  flowtype/require-exact-type: error
  # must have valid flow annotation
  flowtype/require-valid-file-annotation: error
  # type must be in `${PascalCase}Type` form
  flowtype/type-id-match: error

  # enforce consistent usage of `test` and `it` for readibility
  jest/consistent-test-it: error
  # enforce assertion inside test body
  jest/expect-expect:
    - error
    - assertFunctionNames:
        - expect
        - expectSaga

  # disallow commit test with `.only`
  jest/no-focused-tests: error
  # must reuse same test title in same `describe` block
  jest/no-identical-title: error
  # avoid unnecessary importing `jest`
  jest/no-jest-import: error
  # enforce `toStrictEqual()` to check object structure
  jest/prefer-strict-equal: error
  # use `toBeNull()` instead of `toBe(null)`
  jest/prefer-to-be-null: error
  # use `toBeUndefined()` instead of `toBe(undefined)`
  jest/prefer-to-be-undefined: error
  # use `toHaveLength()` instead of checking `length` property explicitly
  jest/prefer-to-have-length: error
  # avoid improper `describe` block
  jest/valid-describe: error
  # avoid improper `expect` statement
  jest/valid-expect: error

  # use `R.T()` instead of `R.always(true)`
  ramda/always-simplification: error
  # use `R.chain` instead of `R.compose(R.flatten, R.map)`
  ramda/compose-simplification: error
  # use `R.eqProps` instead of `R.eqBy(R.prop(_))`
  ramda/eq-by-simplification: error
  # use `R.both`/`R.either` instead of `R.allPass`/`R.anyPass` when there is only two predicates
  ramda/prefer-both-either: error
  # use `R.complement` instead of `R.compose(R.not, ...)`
  ramda/prefer-complement: error

  # must not use current state to deduce next state, since react will manage state asynchronously
  react/no-access-state-in-setstate: error
  # must not use array index as key, it might cause unncessary render
  react/no-array-index-key: error
  # must define only one react component in a file for readability
  react/no-multi-comp: error
  # must not use PureComponent with customized shouldComponentUpdate
  react/no-redundant-should-component-update: error
  # check common typos in react properties and liftcycle methods
  react/no-typos: error
  # must not have `this` in functional components
  react/no-this-in-sfc: error
  # must not use `UNSAFE_` react methods
  react/no-unsafe: error
  # must not have unused props and states
  react/no-unused-prop-types: error
  react/no-unused-state: error
  # enforce empty component to be self closing
  react/self-closing-comp: error
  # enforce component organisation for readability and unity
  react/sort-comp:
    - error
    - order:
        [
          "type-annotations",
          "static-methods",
          "instance-variables",
          "lifecycle",
          "/^handle.+$/",
          "getters",
          "setters",
          "/^(get|set)(?!(InitialState$|DefaultProps$|ChildContext$)).+$/",
          "instance-methods",
          "everything-else",
          "rendering",
        ]
      groups:
        rendering: ["/^render.+$/", "render"]
  # enforce `style` props be an object
  react/style-prop-object: error
  # void DOM element must not have children
  react/void-dom-elements-no-children: error
  # enforce omit `true` to set boolean props
  react/jsx-boolean-value: error
  # avoid error caused by unintended spacing in react children
  react/jsx-child-element-spacing: error
  # enforce event handler naming prefix
  react/jsx-handler-names: error
  # react component must be in PascalCase
  react/jsx-pascal-case: error

  # avoid improper use of `mapDispatchToProps`
  react-redux/mapDispatchToProps-returns-object: error
  # must not return entire `store` from `mapDispatchToProps`, which harm performance
  react-redux/mapStateToProps-no-store: error
  # must not initialize constant objects in `mapDispatchToProps`, which harm performance
  react-redux/mapStateToProps-prefer-hoisted: error
  # enforce parameters naming in `mapStateToProps` for consistency
  react-redux/mapStateToProps-prefer-parameters-names: error