Babel can't parse "for each...in" statement

I'm attempting to transpile Salesforce Commerce Cloud's .ds files to JavaScript so we can apply standard testing tools (Jest, Mocha, etc.). The SFCC docs indicate that .ds files are "Rhino JavaScript", with a non-standard extension for Flow-like type checking.

So far, stripping out the type annotations has been simple, using the transform-flow-strip-types plugin. But SFCC supports a deprecated "for each...in" statement from JavaScript 1.6 that Babel is choking on.

All code below is available on github.

Here's my source src/index.ds file:

function dump(a: Array) {
    for each (var x in a) {
        console.log(x);
    }
}
module.exports = dump;

And my gulfile.js:

const gulp = require('gulp');
const babel = require('gulp-babel');

gulp.task('test', function () {
    gulp.src('src/**/*.ds')
        .pipe(babel())
        .pipe(gulp.dest('dst'));
});

And this is my package.json:

{
  "name": "dspoc",
  "version": "1.0.0",
  "description": "poc",
  "main": "index.ds",
  "author": "cjr",
  "license": "ISC",
  "devDependencies": {
    "babel": "^6.23.0",
    "babel-core": "^6.26.3",
    "babel-plugin-transform-flow-strip-types": "^6.22.0",
    "gulp": "^3.9.1",
    "gulp-babel": "^7.0.1"
  },
  "babel": {
    "plugins": [
      "transform-flow-strip-types"
    ]
  }
}

When I run gulp test, I get this:

%> gulp test
[11:23:06] Using gulpfile ~/dev/dspoc/gulpfile.js
[11:23:06] Starting 'test'...
[11:23:06] Finished 'test' after 9.15 ms

events.js:163
      throw er; // Unhandled 'error' event
      ^
SyntaxError: /Users/craser/dev/dspoc/src/index.ds: Unexpected token, expected ( (2:5)
  1 | function dump(a: Array) {
> 2 |   for each (var x in a) {
    |       ^
  3 |       console.log(x);
  4 |   }
  5 | }
    at Parser.pp$5.raise (/Users/craser/dev/dspoc/node_modules/babylon/lib/index.js:4454:13)
    at Parser.pp.unexpected (/Users/craser/dev/dspoc/node_modules/babylon/lib/index.js:1761:8)
    at Parser.pp.expect (/Users/craser/dev/dspoc/node_modules/babylon/lib/index.js:1749:33)
    at Parser.pp$1.parseForStatement (/Users/craser/dev/dspoc/node_modules/babylon/lib/index.js:2008:8)
    at Parser.pp$1.parseStatement (/Users/craser/dev/dspoc/node_modules/babylon/lib/index.js:1836:19)
    at Parser.parseStatement (/Users/craser/dev/dspoc/node_modules/babylon/lib/index.js:5910:22)
    at Parser.pp$1.parseBlockBody (/Users/craser/dev/dspoc/node_modules/babylon/lib/index.js:2268:21)
    at Parser.pp$1.parseBlock (/Users/craser/dev/dspoc/node_modules/babylon/lib/index.js:2247:8)
    at Parser.pp$3.parseFunctionBody (/Users/craser/dev/dspoc/node_modules/babylon/lib/index.js:4235:22)
    at Parser.parseFunctionBody (/Users/craser/dev/dspoc/node_modules/babylon/lib/index.js:5897:20)

I've spent quite a bit of time digging for a plugin that will let Babel transpile this to something like the for...of statement, but I can't seem to find anything.

I'm now at the precipice of digging into the for-of transform was built and creating something similar to transform for each...in, but I really don't want to have to put that work in if I can avoid it.

I feel like I'm missing something obvious here. Anyone know how this can be done?

Solution

for each...in was never an official part of the spec and didn't exist by the time Babel came around, so it is not supported by Babel. I'm afraid you've have to update all usage of that syntax before Babel will be able to process it.