Fix compatibility with Ember 3.27+ when using compileModules: false.

[rwjblue]

When using libraries that leverage compileModules: false (commonly used to transpile vendor tree's without introducing a wrapping AMD module) on Ember 3.27+ (where we don't transpile away the various @ember/* modules any longer) we would leave the debug module imports alone during transpilation. This resulted (in most cases) in there being a bare unwrapped and untranspiled import statement in vendor.js. This would then fail everything.

This changes the logic slightly to continue transpiling to globals mode when compileModules: false is set.

Note: this is really just a stop gap solution (and will still cause deprecations to be emitted, addons that are currently leveraging compileModules: false will need to make some changes for Ember 4.0 (where a global window.Ember will not be ambiently available).

[scalvert]

Thanks for this, @rwjblue. The comment/test looks good.

[ef4]

I don't think this is complete. It will transpile away import { assert } from '@ember/debug' but it will still leave things like import Ember from 'ember'. The whole modules API polyfill would need the same special handling here, not just the debug macros. But also, embroider stage1 forces compileModules: false. If that starts re-enabling the modules API polyfill even on new ember versions it will cause needless deprecation spew in embroider builds.

People authoring their code as ES modules and then passing it to ember-cli-babel with compileModules: false should not be surprised when they get untranspiled modules! That is exactly the name of the option!

IMO, this PR should be reverted and we should tell people it's their own bug if they're using import and compileModules: false together. It worked by accident on earlier ember versions because ember was "cheating" on modules. Their code was never properly using ES modules anyway, because if they had tried to import anything other than the fake modules it would have blown up.

I can't emphasize strongly enough what a dead-end it is to try to use ES modules in treeForVendor. If you want ES modules, get out of treeForVendor. While you're still in treeForVendor, use Ember global instead of imports.

[ef4]

I have confirmed that this change breaks a wide swath of Embroider's test suite. I think it breaks every app on ember-source 3.27 using embroider.