tests/_setup/isolateDataDir.ts

// Test-only DATA_DIR isolation.
//
// Loaded via `node --import ./tests/_setup/isolateDataDir.ts` from the test/mutation
// invocations (package.json test scripts, stryker.conf.json tap.nodeArgs, the
// quality.yml TIA step, and the CI test jobs) — NEVER from production. It MUST stay
// out of open-sse/utils/setupPolyfill.ts, which is also imported by production
// (bin/omniroute.mjs, proxyFetch.ts, proxyDispatcher.ts) where redirecting DATA_DIR
// would point the live SQLite DB at a throwaway temp dir.
//
// Why: node:test spawns a process per test file and Stryker spawns one per sandbox,
// but every process resolves DATA_DIR to the SAME default (~/.omniroute) when the env
// var is unset (see src/lib/dataPaths.ts::resolveDataDir). Concurrent processes then
// open the SAME on-disk storage.sqlite, causing cross-file state races: SQLite lock
// contention that hangs `test:unit` under high `--test-concurrency`, and the
// non-deterministic baseline that forced Stryker to `concurrency: 1`.
//
// Giving each process its own DATA_DIR under the OS temp dir removes the shared file,
// so concurrent test processes never collide. Tests that set DATA_DIR explicitly keep
// winning — this only fills in an isolated default when none was chosen.
import fs from "node:fs";
import os from "node:os";
import path from "node:path";

if (!process.env.DATA_DIR) {
  const dir = fs.mkdtempSync(path.join(os.tmpdir(), "omniroute-test-"));
  process.env.DATA_DIR = dir;

  // Best-effort cleanup so a long suite run does not leak hundreds of temp DBs.
  process.on("exit", () => {
    try {
      fs.rmSync(dir, { recursive: true, force: true });
    } catch {
      // ignore — the OS reaps its temp dir eventually.
    }
  });
}