Support Babel 8 alongside Babel 7

[wagenet]

This PR was written by Claude (an AI agent), run by @wagenet. The code and the numbers below are the agent's work, not @wagenet's. Please review it as you would any unfamiliar contributor's patch.

Makes ember-auto-import install and run under either @babel/core 7 or 8. I didn't find an existing Babel 8 issue in this repo.

The bug that breaks silently

Babel 8 parses import() into a dedicated ImportExpression node instead of a CallExpression with an Import callee. Both of our plugins keyed off the old shape: analyzer-plugin.ts checked callee.type === 'Import', and babel-plugin.ts had an Import visitor.

Under Babel 8 neither fires, and nothing throws. The analyzer stops seeing dynamic imports, so those deps never enter a bundle, and import() is never rewritten to emberAutoImportDynamic. You'd find out at runtime.

Both plugins now handle both shapes. Babel 7.22+ can emit the Babel 8 AST via the createImportExpressions parser option, so the regression test runs on our normal Babel 7 CI. It fails without the fix.

Config Babel 8 rejects

In cleanBabelConfig():

Was	Now	Why
plugin-proposal-class-properties	plugin-transform-class-properties	7.18.6 is the last proposal release there will ever be, and its @babel/core: ^7.0.0-0 peer is an install failure against core 8
plugin-proposal-private-methods	plugin-transform-private-methods	Same
decorators { legacy: true }	{ version: 'legacy' }	Babel 8 dropped the shorthand and errors without an explicit version. 7.17+ accepts version: 'legacy'
{ loose: false }	omitted	Already the default, and deprecated in Babel 8 in favor of assumptions

Ranges

Babel deps widened to ^7.x || ^8.0.0. Babel 8's plugins declare api.assertVersion("^7.0.0-0 || ^8.0.0"), so a mixed install (core 7 with plugins 8, which is what pnpm produces here) works.

babel-loader goes to ^8.0.6 || ^10.1.1; 8 and 9 both cap @babel/core at ^7. Two side effects worth a look: a fresh install now resolves babel-loader 10 even for Babel 7 users, and its engines (^18.20.0 || ^20.10.0 || >=22.0.0) are narrower than this package's declared 12.* || 14.* || >= 16. That engines field looked stale enough that I left it alone.

broccoli-babel-transpiler: ^8.0.0 is new in devDependencies. The unit tests imported it without declaring it and were getting 7.8.1 by hoisting, which calls babel.transform() with no callback, which Babel 8 rejects. 8.0.2 needs new and { babel: options }, hence the test churn.

TypeScript

Babel 8 ships its own types and renamed things (TransformOptions to InputOptions, PluginObj to PluginObject), so tsc fails outright under it. ts/babel-compat.ts derives the options type from a signature present in both. cleanBabelConfig's plugin list is now PluginItem[], which meant flattening single-element [plugin] entries to bare strings.

Test results

Under @babel/core 8.0.1, preset-env 8.0.2, babel-loader 10.1.1 (forced with pnpm.overrides): 157/157 node unit tests pass. That's the signal that matters, since js/tests drives both plugins and the analyzer through real @babel/core. The new unit_babel8 CI job runs exactly this.

Babel 7 is unregressed: 157/157 unit tests, plus the release-babel, release-dynamic-import, release-static-import, release-import-sync, and indirect-analyzer-skew scenarios.

The full scenario suite can't run under Babel 8 yet, and the blocker isn't here. It dies in ember-cli-babel 8.3.1, which still passes four removed options: { legacy: true } to proposal-decorators, { legacy: true } to transform-class-static-block (which has no such option), regenerator/useESModules to transform-runtime, and moduleId/getModuleId. I patched the first three in node_modules to get further; the build then failed on getModuleId inside a nested qunit-dom/node_modules/ember-cli-babel a local patch can't reach.

Left alone

analyzer.ts has if (this.pack.babelMajorVersion !== 7) throw on the slow analyzer path. That's the ember-cli-babel major, not @babel/core's, so it already throws for anyone on ember-cli-babel 8 who reaches that path. Unrelated to Babel 8, but someone should look at it.

babel-plugin-syntax-dynamic-import is a Babel 6 plugin pushing a dynamicImport parser plugin name. Babel 8 ignores it rather than erroring, so it's harmless.

🤖 Generated with Claude Code