Branching ESLint parser to consume both TypeScript (via typescript-eslint-parser) and JavaScript (via babel-eslint). Usage: in .eslintrc, "parser": "./eslintParserForTypeScriptAndJavaScript.js"

eslintParserForTypeScriptAndJavaScript.js

/* eslint-disable func-names, prefer-arrow-callback */

function isTypeScriptFilePath(filePath) {
  return /\.tsx?$/.test(filePath);
}

function isTypeScriptCode(text) {
  return (
    /^\s*((declare\s+module)|(interface))\s+/m.test(text)
  );
}

function shouldUseTypeScriptParser(text, parserOptions) {
  return (
    isTypeScriptFilePath(parserOptions.filePath)
    // HACK(@sompylasar): While waiting for the updated `eslint-plugin-import` to be released, have to detect TypeScript by file content. https://github.com/benmosher/eslint-plugin-import/pull/840
    // TODO(@sompylasar): Remove this hack and update `eslint-plugin-import` as soon as the PR is merged and released: https://github.com/benmosher/eslint-plugin-import/pull/840
    || (!parserOptions.filePath && isTypeScriptCode(text))
  );
}

function parseTypeScript(text, parserOptions) {
  const ast = require('typescript-eslint-parser').parse(text, parserOptions);

  // WORKAROUND(@sompylasar): Drop `declare module` to prevent its contents from triggering `no-undef`. https://github.com/eslint/typescript-eslint-parser/issues/77#issuecomment-293581001
  ast.body = ast.body.filter(function (node) {
    return (node.type !== 'TSModuleDeclaration');
  });

  // WORKAROUND(@sompylasar): Failsafe for `eslint-plugin-import` TypeError: Cannot read property 'some' of undefined when `ast.comments` is missing on the AST. https://github.com/benmosher/eslint-plugin-import/issues/842
  ast.comments = ast.comments || [];

  return ast;
}

function parseJavaScript(text, parserOptions) {
  const ast = require('babel-eslint').parse(text, parserOptions);
  return ast;
}


module.exports = {
  parse: function (text, parserOptions) {
    if (shouldUseTypeScriptParser(text, parserOptions)) {
      return parseTypeScript(text, parserOptions);
    }

    return parseJavaScript(text, parserOptions);
  },
};