[BUG] Example Dangerfile does not parse with a vue-cli app

Describe the bug When using Danger with an app generated with vue-cli, the example Dangerfile from the documentation fails to parse with SyntaxError: cannot use import statement outside a module.

The output in the GitLab CI log:

$ yarn run danger ci --failOnErrors
yarn run v1.22.5
$ /builds/unikitty37/danger-demo/node_modules/.bin/danger ci --failOnErrors
Unable to evaluate the Dangerfile
 dangerfile.js:1
import "core-js/modules/es.array.join";
^^^^^^
SyntaxError: Cannot use import statement outside a module
    at wrapSafe (internal/modules/cjs/loader.js:991:16)
    at Module._compile (internal/modules/cjs/loader.js:1039:27)
    at Object.requireFromString [as default] (/builds/unikitty37/danger-demo/node_modules/require-from-string/index.js:28:4)
    at Object.<anonymous> (/builds/unikitty37/danger-demo/node_modules/danger/distribution/runner/runners/inline.js:144:63)
    at step (/builds/unikitty37/danger-demo/node_modules/danger/distribution/runner/runners/inline.js:32:23)
    at Object.next (/builds/unikitty37/danger-demo/node_modules/danger/distribution/runner/runners/inline.js:13:53)
    at /builds/unikitty37/danger-demo/node_modules/danger/distribution/runner/runners/inline.js:7:71
    at new Promise (<anonymous>)
    at __awaiter (/builds/unikitty37/danger-demo/node_modules/danger/distribution/runner/runners/inline.js:3:12)
    at Object.exports.runDangerfileEnvironment (/builds/unikitty37/danger-demo/node_modules/danger/distribution/runner/runners/inline.js:105:136)
Failing the build, there is 1 fail.
Feedback: https://gitlab.com/unikitty37/danger-demo/merge_requests/1#note_404292895
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

To Reproduce Steps to reproduce the behaviour:

1. Fork https://gitlab.com/unikitty37/danger-demo, which uses the Dangerfile from https://danger.systems/js/guides/getting_started.html#creating-a-dangerfile
2. Configure the DANGER_GITLAB_API_TOKEN variable in the CI settings
3. Create an MR on the fork

Expected behaviour

The Dangerfile runs, and attaches a comment containing a list of the modified files.

Screenshots n/a

Your Environment

software	version
danger.js	10.4.0
node	14.5.0
yarn	1.22.4
Operating System	Docker container node:14-alpine

Additional context I’m not sure if Danger is transpiling correctly — vue-cli sets up projects with Babel by default, but https://danger.systems/js/tutorials/transpilation.html doesn’t really give me much of a clue on how to debug this…

[themojilla]

While the issue is already being closed if anyone struggles with this issue just add the join polyfills in the babel.config.js. this will do the trick.

module.exports = {
  presets: [
    ['@vue/cli-plugin-babel/preset', {
      polyfills: [
        'es.array.join',
      ],
    }],
  ],
};

[YasiOnFire]

Same problem, similar setup (vue). Dind’t work either in CI or locally. I’ve tried to debug the source provided by @orta, but with no luck. However just changed dangerfile to typescript and everything works in CI as well as locally.