feat: add vite-layers

vite-layers/test/kit.test.ts

@@ -0,0 +1,95 @@
+import { fileURLToPath } from 'node:url'
+import { dirname, resolve } from 'node:path'
+import { describe, expect, it } from 'vitest'
+import type { Plugin, UserConfig, UserConfigFnObject } from 'vite'
+import { buildViteConfig, dedupePlugins } from '../src/kit'
+
+const here = dirname(fileURLToPath(import.meta.url))
+const fixture = (p: string) => resolve(here, 'fixtures', p).replace(/\\/g, '/')
+const env = { command: 'build', mode: 'production', isSsrBuild: false, isPreview: false } as const
+
+async function build(appDir: string): Promise<UserConfig> {
+  const fn = (await buildViteConfig(appDir)) as UserConfigFnObject
+  return (await fn(env)) as UserConfig
+}
+
+describe('buildViteConfig', () => {
+  it('exposes merged features via __FEATURES__ define (for DCE)', async () => {
+    const cfg = await build(fixture('stack/app'))
+    const features = JSON.parse((cfg.define as Record<string, string>).__FEATURES__)
+    expect(features.shared).toBe('app')
+    expect(features).toMatchObject({ app: true, base: true, core: true })
+  })
+
+  it('emits dotted feature defines (for dead-code elimination of gated imports)', async () => {
+    const cfg = await build(fixture('stack/app'))
+    const define = cfg.define as Record<string, string>
+    // dotted entry is folded by esbuild to a literal → enables DCE of `__FEATURES__.x ? import() : []`
+    expect(define['__FEATURES__.shared']).toBe('"app"')
+    expect(define['__FEATURES__.app']).toBe('true')
+  })
+
+  it('emits dotted defines at every nesting depth (so nested flags also DCE)', async () => {
+    const cfg = await build(fixture('features/app'))
+    const define = cfg.define as Record<string, string>
+    expect(define['__FEATURES__.billing']).toBe('false')
+    expect(define['__FEATURES__.nested.enabled']).toBe('false') // deep leaf → foldable → DCE-able
+    expect(define['__FEATURES__.nested.deep.on']).toBe('true')
+    expect(define['__FEATURES__.nested']).toBe('{"enabled":false,"deep":{"on":true}}') // intermediate object too
+  })
+
+  it('skips non-identifier feature keys in dotted defines (avoids INVALID_DEFINE_CONFIG crash)', async () => {
+    const cfg = await build(fixture('features/app'))
+    const define = cfg.define as Record<string, string>
+    // a dotted define with `kebab-flag` would crash the build; it is skipped here…
+    expect(define['__FEATURES__.kebab-flag']).toBeUndefined()
+    // …but still readable at runtime via the whole-object define.
+    expect(JSON.parse(define.__FEATURES__)['kebab-flag']).toBe(true)
+  })
+
+  it('runs lifecycle hooks: layers:resolved mutates features (before define), vite:config mutates config', async () => {
+    const fn = (await buildViteConfig(fixture('stack/app'), {
+      hooks: {
+        'layers:resolved': s => void ((s.merged.features ??= {}).injected = true),
+        'vite:config': ctx => void (ctx.config.define = { ...ctx.config.define, INJECTED: '"yes"' }),
+      },
+    })) as UserConfigFnObject
+    const cfg = (await fn(env)) as UserConfig
+    const define = cfg.define as Record<string, string>
+    expect(define['__FEATURES__.injected']).toBe('true') // layers:resolved ran before featureDefines
+    expect(define.INJECTED).toBe('"yes"') // vite:config ran at the very end
+  })
+
+  it('registers the layers resolver plugin', async () => {
+    const cfg = await build(fixture('stack/app'))
+    const plugins = (cfg.plugins as Plugin[]).flat(Infinity as 1) as Plugin[]
+    expect(plugins.some(p => p?.name === 'vite-layers:resolve')).toBe(true)
+  })
+
+  it('sets ~~/@@ to the project rootDir and #layers/<name> per layer', async () => {
+    const cfg = await build(fixture('stack/app'))
+    const alias = (cfg.resolve as { alias: Record<string, string> }).alias
+    expect(alias['~~']).toBe(fixture('stack/app'))
+    expect(alias['@@']).toBe(fixture('stack/app'))
+    expect(alias['#layers/app']).toBe(fixture('stack/app'))
+    expect(alias['#layers/base']).toBe(fixture('stack/base'))
+    expect(alias['#layers/core']).toBe(fixture('stack/core'))
+  })
+
+  it('defaults outDir to dist/<app>', async () => {
+    const cfg = await build(fixture('stack/app'))
+    expect((cfg.build as { outDir: string }).outDir).toBe('dist/app')
+  })
+})
+
+describe('dedupePlugins', () => {
+  it('removes plugins sharing a name, keeping the later (higher-priority) instance in place', () => {
+    const a: Plugin = { name: 'vue', apply: 'build' }
+    const b: Plugin = { name: 'vue', apply: 'serve' }
+    const other: Plugin = { name: 'other' }
+    const out = dedupePlugins({ plugins: [a, other, b] }).plugins as Plugin[]
+    expect(out).toHaveLength(2)
+    expect(out[0]).toBe(b) // position of first 'vue', value of later one
+    expect(out[1]).toBe(other)
+  })
+})