[Feature Request] Allow specifying parser per file extension

Tell us about your environment

• ESLint Version: ^3.x.x
• Node Version: latest
• npm Version: latest

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

Proposal It would be beneficial to include the ability for eslint to determine which parser to use based on file extension so that eslint can be run against a multi-language codebase in a single pass. By extension this would also benefit text editors that can’t currently specify multiple configs so that a single config can be used to check the entire project.

Right now, I am running eslint once for JS(X), and again for Typescript each using a different parser since the ts-parser doesn’t support most stage-X ecma features and the babel-parser doesn’t support TS syntax.

[kaicataldo]

This does seem useful to me now that we’re actively supporting more parsers (TypeScript, Babel, and now Vue!).

One idea: the parser option could accept an object that maps the parser to a filetype and its parser options:

{
  "parser": {
    "typescript-eslint-parser": {
      "filetypes": [".ts"],
      "parserOptions": {}
    },
    "vue-eslint-parser": {
      "filetypes": [".vue", ".js"],
      "parserOptions": {}
    }
  }
}

Curious what other team members think!

[mightyiam]

Great. Now I know how to deprecate an npm package.