Duplicate key error on computed property from RegExp literals

[lleaff]

Tell us about your environment

• ESLint Version: v3.19.0
• Node Version: v7.7.2
• npm Version: 4.1.2

What parser (default, Babel-ESLint, etc.) are you using?
babel-eslint
Please show your full configuration:

module.exports = {
  "parser": "babel-eslint",

  "globals": {
    "React": true,
    "ReactDOM": true,
    "$": true,
    "_": true,
    "jQuery": true,
  },

  "env": {
    "es6": true,
    "node": true,
    "browser": true,
    "mocha": true,
  },

  "plugins": ["react"],

  "rules": {
    // "indent": [2, 2],
    "linebreak-style": [2, "unix"],
    "semi": [1, "always"], // Enfore semi-colons after statements
    "no-console": [0], // Disallow usage of console API (default 2)
    "no-unused-vars": [1,
      { "vars": "local", // local | all
        "argsIgnorePattern": "^_",
        "args": "after-used", // "after-used": Allow unused params if they come before a used param in the arg list
      }], // Warn against unused variables
    "comma-dangle": [1, "always-multiline"], // Disallow or enforce trailing comma in array literals, e.g.: "always-multiline"
    "no-cond-assign": [1], // Disallow `if (myVar = smth())`

    // eslint-plugin-react
    //------------------------------------------------------------
    "react/display-name": 0, // Prevent missing displayName in a React component definition
    "react/jsx-no-undef": 2, // Disallow undeclared variables in JSX
    "react/jsx-sort-props": 0, // Enforce props alphabetical sorting
    "react/jsx-uses-react": 2, // Prevent React to be incorrectly marked as unused
    "react/jsx-uses-vars": 2, // Prevent variables used in JSX to be incorrectly marked as unused
    "react/no-did-mount-set-state": 2, // Prevent usage of setState in componentDidMount
    "react/no-did-update-set-state": 2, // Prevent usage of setState in componentDidUpdate
    "react/no-multi-comp": 0, // Prevent multiple component definition per file
    "react/no-unknown-property": 2, // Prevent usage of unknown DOM property
    "react/prop-types": 0, // Prevent missing props validation in a React component definition (propTypes)
    "react/react-in-jsx-scope": 2, // Prevent missing React when using JSX
    "react/self-closing-comp": 2, // Prevent extra closing tags for components without children
    //"react/wrap-multilines": 2, // Prevent missing parentheses around multilines JSX // Disabled cause eslint doesn't find the rule (even tho it's documented)

  },

  "extends": ["eslint:recommended"],
};

What did you do? Please include the actual source code causing the issue.

const foo = {
  [/bar/]: '/bar/',
  [/foo/]: '/foo/',
};

What did you expect to happen?
No error as default toString implementation of RegExp produces different results from different RegExp literals.

What actually happened? Please include the actual, raw output from ESLint.

  3:4  error    Duplicate key '[object Object]'  no-dupe-keys

✖ 1 problem (1 error, 0 warnings)

---

I don't know how practical this would be to implement, but since keys from array literals are correctly differentiated, I'm assuming this shouldn't be hard.

[soda0289]

The prop value is cast to a string in the rule no-dupe-key

eslint/lib/ast-utils.js

Line 896 in 735d02d

return String(prop.value);

I tested the code sample on the eslint demo, which uses the espree parser, and it works as expected. It could be that babel-eslint is not generating a RegExp object for the value of Literal nodes.

[soda0289]

This is a bug with babel-eslint. When they convert the RegExpLiteral they only set value to an empty Object {} and not to a RegExp Object.
https://github.com/babel/babel-eslint/blob/master/babylon-to-espree/toAST.js#L97

I fixed a similar bug in typescript-eslint-parser I can work on a fix for babel soon.

[soda0289]

Fix landed in babel-eslint