breaks are transpiled to return inside then

Current Behavior

While working on my code I noticed a bug that led to my transpiled files and I saw that tsdx was incorrectly transforming my break inside switch cases to return. I thoughts that was rather odd so I created a sample project with the following code to pinpoint the issue:

function wait() {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve();
    }, 1000);
  });
}

export const test = async () => {
  await wait();
  switch ('' as any) {
    case 'a':
      break;
    case 'b':
      break;
    default:
      break;
  }
  const foo = { bar: true };
  console.log('foo :', foo);
};

When running tsdx build, this is what I get:

'use strict';

Object.defineProperty(exports, '__esModule', { value: true });

function wait() {
  return new Promise(function (resolve, reject) {
    setTimeout(function () {
      resolve();
    }, 1000);
  });
}

var test = function test() {
  try {
    return Promise.resolve(wait()).then(function () {
      switch ('') {
        case 'a':
          return;

        case 'b':
          return;

        default:
          return;
      }

      var foo = {
        bar: true
      };
      console.log('foo :', foo);
    });
  } catch (e) {
    return Promise.reject(e);
  }
};

exports.test = test;
//# sourceMappingURL=switch-test.cjs.development.js.map

As you can see, inside test, breaks inside then are transformed to returns, which is NOT correct. The console.log line would never be reached.

Expected behavior

breaks inside then should stay breaks.

Suggested solution(s)

No idea. The problem may come from babel or rollrup or one of their plugins. Any idea what may cause the problem?

Your environment

Software	Version(s)
TSDX	0.12.3
TypeScript	^3.7.5
Browser
npm/Yarn	yarn 1.19.1
Node	10.16.3
Operating System	Linux, but same behavior on windows

[agilgur5]

Another comment on that issue revealing more broken code: https://github.com/rpetrich/babel-plugin-transform-async-to-promises/issues/49#issuecomment-656050437. And still no response / maintenance.

At this point, I think it would be optimal to switch to regenerator because at least the code it produces is actually correct and not broken in subtle, hard-to-detect ways. I’m also not sure really how much difference in weight it adds as a polyfill because babel-plugin-transform-async-to-promises also adds helpers, it’s not just a polyfill vs. no polyfill comparison.

[agilgur5]

async-to-promises has been replaced with babel-plugin-polyfill-regenerator in #795 and will be released in v0.14.0 soon. It will only pure polyfill generators for targets that need a polyfill according to your browserslistrc or preset-env targets