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no-unneeded-ternary with arrow function results in parsing error #11579

noisyscanner opened this issue Apr 2, 2019 · 1 comment


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commented Apr 2, 2019

What version of eslint?
What operating system, Node.js, and npm version?
Mac OS X Mojave ⬢ 8.11.2 📦 5.6.0

What parser (default, Babel-ESLint, etc.) are you using?
babel-eslint 9.0.0

Using the no-unneeded-ternary rule.
When formatting code that is using a ternary like below, the function is not wrapped, causing a parse error and fails.

const foo = true
const bar = foo ? foo : () => {}

Causes this error

  2:21  error  Parsing error: Unexpected token

  1 | const foo = true
> 2 | const bar = foo || () => {}
    |                     ^
  3 |

✖ 1 problem (1 error, 0 warnings)


const bar = foo || (() => {})

Please show your full configuration:
I am using standardJS 12.0.1, which sets the config as follows:

  "parserOptions": {
    "ecmaVersion": 2018,
    "ecmaFeatures": {
      "jsx": true
    "sourceType": "module"

  "env": {
    "es6": true,
    "node": true

  "plugins": [

  "globals": {
    "document": false,
    "navigator": false,
    "window": false

  "rules": {
    "accessor-pairs": "error",
    "arrow-spacing": ["error", { "before": true, "after": true }],
    "block-spacing": ["error", "always"],
    "brace-style": ["error", "1tbs", { "allowSingleLine": true }],
    "camelcase": ["error", { "properties": "never" }],
    "comma-dangle": ["error", {
      "arrays": "never",
      "objects": "never",
      "imports": "never",
      "exports": "never",
      "functions": "never"
    "comma-spacing": ["error", { "before": false, "after": true }],
    "comma-style": ["error", "last"],
    "constructor-super": "error",
    "curly": ["error", "multi-line"],
    "dot-location": ["error", "property"],
    "eol-last": "error",
    "eqeqeq": ["error", "always", { "null": "ignore" }],
    "func-call-spacing": ["error", "never"],
    "generator-star-spacing": ["error", { "before": true, "after": true }],
    "handle-callback-err": ["error", "^(err|error)$" ],
    "indent": ["error", 2, {
      "SwitchCase": 1,
      "VariableDeclarator": 1,
      "outerIIFEBody": 1,
      "MemberExpression": 1,
      "FunctionDeclaration": { "parameters": 1, "body": 1 },
      "FunctionExpression": { "parameters": 1, "body": 1 },
      "CallExpression": { "arguments": 1 },
      "ArrayExpression": 1,
      "ObjectExpression": 1,
      "ImportDeclaration": 1,
      "flatTernaryExpressions": false,
      "ignoreComments": false
    "key-spacing": ["error", { "beforeColon": false, "afterColon": true }],
    "keyword-spacing": ["error", { "before": true, "after": true }],
    "new-cap": ["error", { "newIsCap": true, "capIsNew": false }],
    "new-parens": "error",
    "no-array-constructor": "error",
    "no-caller": "error",
    "no-class-assign": "error",
    "no-compare-neg-zero": "error",
    "no-cond-assign": "error",
    "no-const-assign": "error",
    "no-constant-condition": ["error", { "checkLoops": false }],
    "no-control-regex": "error",
    "no-debugger": "error",
    "no-delete-var": "error",
    "no-dupe-args": "error",
    "no-dupe-class-members": "error",
    "no-dupe-keys": "error",
    "no-duplicate-case": "error",
    "no-empty-character-class": "error",
    "no-empty-pattern": "error",
    "no-eval": "error",
    "no-ex-assign": "error",
    "no-extend-native": "error",
    "no-extra-bind": "error",
    "no-extra-boolean-cast": "error",
    "no-extra-parens": ["error", "functions"],
    "no-fallthrough": "error",
    "no-floating-decimal": "error",
    "no-func-assign": "error",
    "no-global-assign": "error",
    "no-implied-eval": "error",
    "no-inner-declarations": ["error", "functions"],
    "no-invalid-regexp": "error",
    "no-irregular-whitespace": "error",
    "no-iterator": "error",
    "no-label-var": "error",
    "no-labels": ["error", { "allowLoop": false, "allowSwitch": false }],
    "no-lone-blocks": "error",
    "no-mixed-operators": ["error", {
      "groups": [
        ["==", "!=", "===", "!==", ">", ">=", "<", "<="],
        ["&&", "||"],
        ["in", "instanceof"]
      "allowSamePrecedence": true
    "no-mixed-spaces-and-tabs": "error",
    "no-multi-spaces": "error",
    "no-multi-str": "error",
    "no-multiple-empty-lines": ["error", { "max": 1, "maxEOF": 0 }],
    "no-negated-in-lhs": "error",
    "no-new": "error",
    "no-new-func": "error",
    "no-new-object": "error",
    "no-new-require": "error",
    "no-new-symbol": "error",
    "no-new-wrappers": "error",
    "no-obj-calls": "error",
    "no-octal": "error",
    "no-octal-escape": "error",
    "no-path-concat": "error",
    "no-proto": "error",
    "no-redeclare": "error",
    "no-regex-spaces": "error",
    "no-return-assign": ["error", "except-parens"],
    "no-return-await": "error",
    "no-self-assign": "error",
    "no-self-compare": "error",
    "no-sequences": "error",
    "no-shadow-restricted-names": "error",
    "no-sparse-arrays": "error",
    "no-tabs": "error",
    "no-template-curly-in-string": "error",
    "no-this-before-super": "error",
    "no-throw-literal": "error",
    "no-trailing-spaces": "error",
    "no-undef": "error",
    "no-undef-init": "error",
    "no-unexpected-multiline": "error",
    "no-unmodified-loop-condition": "error",
    "no-unneeded-ternary": ["error", { "defaultAssignment": false }],
    "no-unreachable": "error",
    "no-unsafe-finally": "error",
    "no-unsafe-negation": "error",
    "no-unused-expressions": ["error", { "allowShortCircuit": true, "allowTernary": true, "allowTaggedTemplates": true }],
    "no-unused-vars": ["error", { "vars": "all", "args": "none", "ignoreRestSiblings": true }],
    "no-use-before-define": ["error", { "functions": false, "classes": false, "variables": false }],
    "no-useless-call": "error",
    "no-useless-computed-key": "error",
    "no-useless-constructor": "error",
    "no-useless-escape": "error",
    "no-useless-rename": "error",
    "no-useless-return": "error",
    "no-whitespace-before-property": "error",
    "no-with": "error",
    "object-curly-spacing": ["error", "always"],
    "object-property-newline": ["error", { "allowMultiplePropertiesPerLine": true }],
    "one-var": ["error", { "initialized": "never" }],
    "operator-linebreak": ["error", "after", { "overrides": { "?": "before", ":": "before" } }],
    "padded-blocks": ["error", { "blocks": "never", "switches": "never", "classes": "never" }],
    "prefer-promise-reject-errors": "error",
    "quotes": ["error", "single", { "avoidEscape": true, "allowTemplateLiterals": true }],
    "rest-spread-spacing": ["error", "never"],
    "semi": ["error", "never"],
    "semi-spacing": ["error", { "before": false, "after": true }],
    "space-before-blocks": ["error", "always"],
    "space-before-function-paren": ["error", "always"],
    "space-in-parens": ["error", "never"],
    "space-infix-ops": "error",
    "space-unary-ops": ["error", { "words": true, "nonwords": false }],
    "spaced-comment": ["error", "always", {
      "line": { "markers": ["*package", "!", "/", ",", "="] },
      "block": { "balanced": true, "markers": ["*package", "!", ",", ":", "::", "flow-include"], "exceptions": ["*"] }
    "symbol-description": "error",
    "template-curly-spacing": ["error", "never"],
    "template-tag-spacing": ["error", "never"],
    "unicode-bom": ["error", "never"],
    "use-isnan": "error",
    "valid-typeof": ["error", { "requireStringLiterals": true }],
    "wrap-iife": ["error", "any", { "functionPrototypeMethods": true }],
    "yield-star-spacing": ["error", "both"],
    "yoda": ["error", "never"],

    "import/export": "error",
    "import/first": "error",
    "import/no-duplicates": "error",
    "import/no-named-default": "error",
    "import/no-webpack-loader-syntax": "error",

    "node/no-deprecated-api": "error",
    "node/process-exit-as-throw": "error",

    "promise/param-names": "error",

    "standard/array-bracket-even-spacing": ["error", "either"],
    "standard/computed-property-even-spacing": ["error", "even"],
    "standard/no-callback-literal": "error",
    "standard/object-curly-even-spacing": ["error", "either"]
npx eslint theFile.js

Are you willing to submit a pull request to fix this bug?
Tbh I wouldn't know where to start, sorry.

Originally opened this in standardJS repo but seems like an eslint issue so re-opening here.


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commented Apr 11, 2019

Thank you for the report.

I could reproduce this on our online demo.
Yes, it's a bug to fix.

@mysticatea mysticatea self-assigned this Apr 13, 2019

mysticatea added a commit that referenced this issue Apr 13, 2019

mysticatea added a commit that referenced this issue Apr 19, 2019

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