bench-config.js

/**
 * Merges BENCH_* environment variables (set by scripts/bench.mjs) over the
 * app's own defaults, so one committed vitest.config.ts serves every matrix
 * cell without depending on CLI flags that drift across Vitest versions.
 *
 * Recognized variables:
 *   BENCH_POOL             forks | threads | vmThreads | vmForks
 *   BENCH_ENV              node | jsdom | happy-dom
 *   BENCH_ISOLATE          true | false
 *   BENCH_FILE_PARALLELISM true | false
 *   BENCH_MAX_WORKERS      number or percentage string ('50%')
 *   BENCH_FS_CACHE         true | false (always set explicitly by the runner —
 *                          the default flipped across Vitest versions)
 *   BENCH_FS_CACHE_MODE    stable (top-level `fsModuleCache`, Vitest > 4.1) |
 *                          experimental (`experimental.fsModuleCache`, <= 4.1)
 *   BENCH_COVERAGE         v8 | istanbul
 *   BENCH_BROWSER          true — run in headless Chromium via playwright
 *                          (only apps that pass a loader to benchBrowser)
 */
export function benchTest(defaults = {}) {
  const e = process.env
  const test = { ...defaults }
  const bool = v => !['false', '0'].includes(v)

  if (e.BENCH_POOL)
    test.pool = e.BENCH_POOL
  if (e.BENCH_ENV)
    test.environment = e.BENCH_ENV
  if (e.BENCH_ISOLATE)
    test.isolate = bool(e.BENCH_ISOLATE)
  if (e.BENCH_FILE_PARALLELISM)
    test.fileParallelism = bool(e.BENCH_FILE_PARALLELISM)
  if (e.BENCH_MAX_WORKERS) {
    test.maxWorkers = e.BENCH_MAX_WORKERS.endsWith('%')
      ? e.BENCH_MAX_WORKERS
      : Number(e.BENCH_MAX_WORKERS)
  }
  if (e.BENCH_FS_CACHE) {
    const enabled = bool(e.BENCH_FS_CACHE)
    if (e.BENCH_FS_CACHE_MODE === 'experimental')
      test.experimental = { ...test.experimental, fsModuleCache: enabled }
    else
      test.fsModuleCache = enabled
  }
  if (e.BENCH_COVERAGE)
    test.coverage = { enabled: true, provider: e.BENCH_COVERAGE }

  return test
}

/**
 * Returns the `browser` part of the test config when BENCH_BROWSER is set.
 * The provider package is loaded lazily through the app-supplied loader so
 * node-pool cells don't pay its import cost:
 *
 *   test: {
 *     ...benchTest({ ... }),
 *     ...await benchBrowser(() => import('@vitest/browser-playwright')),
 *   }
 */
export async function benchBrowser(loadProvider) {
  const enabled = process.env.BENCH_BROWSER
  if (!enabled || ['false', '0'].includes(enabled))
    return {}
  const { playwright } = await loadProvider()
  return {
    browser: {
      enabled: true,
      provider: playwright(),
      instances: [{ browser: 'chromium' }],
      headless: true,
    },
  }
}