RFC: deprecate MU support

[chriskrycho]

Given that MU has been officially declared dead, and in the interest of eliminating at least some of our debt in the short term (since we unfortunately don't yet have a good solution implemented for #71), I propose we officially deprecate support and remove it in a future release.

Given we're just about to cut a major, I propose we cut the major and deprecate in the major, i.e. 3.0.0 formally deprecates MU support. In this thread, we can discuss the timeline—how long should users be guaranteed support before the deprecation becomes a breaking change by way of removal?

(Also, if there are objections, I'm up for hearing them, but I think this should be relatively uncontroversial; the sooner we can get MU support out of everything the lower everyone's maintenance burden will be!)

Related

• Update on Module Unification
• typed-ember/ember-cli-typescript-blueprints#100

[dfreeman]

Sounds good to me. I think this should just be a matter of updating/dropping blueprints (and optionally deleting one "custom project layout" test), since the build and typechecking pipeline is layout agnostic now.

[chriskrycho]

That's what I thought was the case, so glad to hear it confirmed. 👍🏼

[dfreeman]

A quick update here! Since removing MU support in ember-cli-typescript only amounts to blueprint changes and MU itself has been declared dead for a number of months, the Typed Ember team decided while planning for the 3.0 release to go ahead and drop the MU blueprints with 3.0.

Projects using MU should continue to build and typecheck correctly with ember-cli-typescript@3 by virtue of the fact that we use tsconfig.json as the source of truth when determining project layout, but active projects still using MU may want to consider migrating anyway, given the broader ecosystem direction indicated by the posts Chris linked above 🙂

[chriskrycho]

Closing because we did this! 🎉 (…a while ago. We're, uhh, behind. 😆)