ember-cli 6.1, eslint 9, eslint flat config, RFC#1055

[NullVoxPopuli]

If anyone wishes to create new addons with 6.1 in the mean time:

git clone git@github.com:embroider-build/addon-blueprint.git
cd addon-blueprint
git checkout update-ember-cli
pnpm install
cd ../
npx ember-cli@latest addon my-addon-name --blueprint ./addon-blueprint --pnpm --typescript
cd my-addon-name
# delete all the ember-data stuff from package.json and tsconfig.json

---

We can't have multiple versions of eslint in a monorepo

Closes:

• ESLint 9 + flat configs #309
• Run prettier separately #183

Related:

• [ENHANCEMENT] Vanilla Prettier setup in blueprints [RFC 1055] ember-cli/ember-cli#10596

UPDATE! below was previously blocking stuff -- ember-data hasn't published types correctly, but this PR removes ember-data types from the tsconfig.json, so it's not blocking. See below links for work tracking addressing the underlying issues.

---

• 6.1, ember-data TS config is broken in monorepo when using npm or yarn@1 ember-cli/ember-cli#10611
  • [BUGFIX release]: tsconfig.json referenced paths to types instead of imports ember-cli/ember-cli#10612
  • Related:
    • Add tests for usage in npm and yarn repos emberjs/data#9630
    • Add smoke-tests for types, build, etc  emberjs/data#9633
    • Add new flag for new: --ember-data (default), and --no-ember-data ember-cli/ember-cli#10613
      • blocked by Release 4.2 breaks support for node 18 adding a dependency which requires node 20  jsdom/cssstyle#181 (because ember-cli's CI is failing right now due to this)

Tangents, potentially not-blocking

• Drop support for yarn@1, set packageManager field in package.json (pnpm 10.x, npm 11.x) #322
• Add @glimmer/component and @ember/test-waiters #317

[sukima]

Will this PR allow addon authors to run this and have it just work out of the box? Is this incantation documented anywhere?

npx ember-cli@latest addon \
  my-addon \
  --blueprint @embroider/addon-blueprint \
  --pnpm \
  --typescript

[sukima]

Is this related to #219 ?

[NullVoxPopuli]

Will this PR allow addon authors to run this and have it just work out of the box?

Correct. We're at a weird time right now, because ember-cli broke this blueprint in its 6.1 release.

Is this incantation documented anywhere?

This repo's readme