feat: add vite-layers

vite-layers/test/public.test.ts

@@ -0,0 +1,37 @@
+import { fileURLToPath } from 'node:url'
+import { dirname, resolve } from 'node:path'
+import { describe, expect, it } from 'vitest'
+import { publicLayersPlugin } from '../src/public'
+
+const here = dirname(fileURLToPath(import.meta.url))
+const fixture = (p: string) => resolve(here, 'fixtures', p)
+
+const callConfig = (p: { config?: unknown }) => (p.config as () => unknown)()
+
+function runGenerateBundle(p: { generateBundle?: unknown }): Record<string, string> {
+  const emitted: Record<string, string> = {}
+  const ctx = {
+    emitFile: ({ fileName, source }: { fileName: string; source: Buffer | string }) => {
+      emitted[fileName] = source.toString()
+    },
+  }
+  ;(p.generateBundle as (this: unknown, ...a: unknown[]) => void).call(ctx, {}, {}, false)
+  return emitted
+}
+
+describe('publicLayersPlugin', () => {
+  const high = fixture('public/high/public')
+  const low = fixture('public/low/public')
+
+  it('disables Vite publicDir when layers have public/, otherwise no-op', () => {
+    expect(callConfig(publicLayersPlugin([high, low]))).toEqual({ publicDir: false })
+    expect(callConfig(publicLayersPlugin([fixture('public/none/public')]))).toBeUndefined()
+  })
+
+  it('emits assets first-match-wins (higher overrides, lower fills gaps, nested ok)', () => {
+    const emitted = runGenerateBundle(publicLayersPlugin([high, low]))
+    expect(emitted['logo.svg']).toBe('HIGH_LOGO') // overridden by the higher layer
+    expect(emitted['shared.txt']).toBe('LOW_SHARED') // inherited from the lower layer
+    expect(emitted['img/icon.svg']).toBe('LOW_ICON') // nested, from the lower layer
+  })
+})