[3.0.1] Failed to load parser errors with ESLint v6

[SamChou19815]

Repro

package.json:

{
  "dependencies": {
    "@typescript-eslint/eslint-plugin": "^3.0.1",
    "@typescript-eslint/parser": "^3.0.1",
    "eslint": "^6.8.0",
    "typescript": "^3.9.3"
  }
}

{
  "parser": "@typescript-eslint/parser",
  "plugins": ["@typescript-eslint"]
}

const f = (): number => 42;

Command: yarn eslint ok.ts

Expected Result

No error.

Actual Result

yarn eslint ok.ts
yarn run v1.22.4
warning package.json: No license field
$ /Users/sam/Downloads/ttt/node_modules/.bin/eslint ok.ts
TypeError: Failed to load parser '@typescript-eslint/parser' declared in '.eslintrc': Class extends value undefined is not a constructor or null
    at Object.<anonymous> (/Users/sam/Downloads/ttt/node_modules/@typescript-eslint/experimental-utils/dist/ts-eslint/ESLint.js:14:31)
    at Module._compile (/Users/sam/Downloads/ttt/node_modules/v8-compile-cache/v8-compile-cache.js:194:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:991:10)
    at Module.load (internal/modules/cjs/loader.js:811:32)
    at Function.Module._load (internal/modules/cjs/loader.js:723:14)
    at Module.require (internal/modules/cjs/loader.js:848:19)
    at require (/Users/sam/Downloads/ttt/node_modules/v8-compile-cache/v8-compile-cache.js:161:20)
    at Object.<anonymous> (/Users/sam/Downloads/ttt/node_modules/@typescript-eslint/experimental-utils/dist/ts-eslint/index.js:15:14)
    at Module._compile (/Users/sam/Downloads/ttt/node_modules/v8-compile-cache/v8-compile-cache.js:194:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:991:10)
error Command failed with exit code 2.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

Additional Info

If I edit the node_modules and remove the line __exportStar(require("./ESLint"), exports); (export * from './ESLint'; in ts source) in node_modules/@typescript-eslint/experimental-utils/dist/ts-eslint/index.js, the error goes away.

I think it should not be exported to the top-level without guard, since the jsdoc for the class clearly says it's only in ESLint v7, and v3 still claims to support ESLint v6.

typescript-eslint/packages/experimental-utils/src/ts-eslint/ESLint.ts

Lines 344 to 352 in a71b9c9

	/**
	* The ESLint class is the primary class to use in Node.js applications.
	* This class depends on the Node.js fs module and the file system, so you cannot use it in browsers.
	*
	* If you want to lint code on browsers, use the Linter class instead.
	*
	* @since 7.0.0
	*/
	class ESLint extends (ESLintESLint as typeof ESLintBase) {}

Versions

package	version
@typescript-eslint/experimental-utils	3.0.1
TypeScript	3.9.3
node	12.14.1
npm	6.14.3

[Towerism]

This will cause all new projects scaffolded with eslint --init errors unless users downgrade the plugin to 3.0.0. They will get a warning if they want to use latest typescript version though.

[djejaquino]

@Towerism downgrading to 3.0.0 worked for me, thanks.

Shouldn't it be backward compatible, since it is a patch version?

[bradzacher]

This has been fixed in master (and is available on the canary tag on npm).
It will be released to latest in due course.