apps/memos-local-plugin: viewer i18n locale default is untestable under Node (detectDefault reads navigator.language at module init)

[chiefmojo]

Summary

apps/memos-local-plugin/viewer/src/stores/i18n.ts computes the module-level default locale at import time:

function detectDefault(): Locale {
  try {
    const saved = localStorage.getItem(STORAGE_KEY);
    if (saved === "en" || saved === "zh") return saved;
  } catch {
    // ignore
  }
  const nav = (typeof navigator !== "undefined" && navigator.language) || "en";
  return nav.toLowerCase().startsWith("zh") ? "zh" : "en";
}

export const locale = signal<Locale>(detectDefault());

Under Node (Vitest / SSR / CI without jsdom), navigator is undefined and localStorage throws (swallowed by the try/catch), so locale is always "en". Any unit test that needs to assert zh-CN strings (e.g. "已连接") can never pass through the real detection path — tests must pin locale.value = "zh" by reaching into the store internals.

Proposal

Make the default injectable / SSR-safe so tests (and SSR hosts) can exercise the detection logic without mutating the exported signal, e.g.:

export function detectDefault(opts?: { navLanguage?: string; storageKey?: string }): Locale

or lazy-evaluate detectDefault so a test can stub globalThis.navigator before first read.

Either keeps the browser behavior identical while letting tests cover the zh-* → zh branch that currently ships untested.

Happy to send a small PR if you'd like — we have one ready downstream.

[Memtensor-AI]

🤖 AutoDev has picked up this issue and started working on it.

Task ID: f0c5eb3814b42e21
Working branch: bugfix/autodev-2346-20260907141702290
Target branch: latest dev* branch
Workflow: opsp (analysis → coding → testing → PR)

I will post the PR link here once done. If I need more information, I will ask in the comments.

[Memtensor-AI]

✅ AutoDev task f0c5eb3814b42e21 completed.

Summary: Fixes #2346 — apps/memos-local-plugin viewer i18n detectDefault is now injectable so the zh-* → "zh" branch is testable under Node/Vitest/SSR.

Root cause. viewer/src/stores/i18n.ts defined detectDefault() as a module-private function that read navigator.language and localStorage directly. Under Node these globals are absent (localStorage access throws, swallowed by try/catch), so the module-level locale signal always initialised to "en" and the zh-* branch was unreachable from unit tests. Any test needing zh strings had to reach into the store and mutate locale.value = "zh" (see tests/unit/viewer/restart-copy.test.ts for the current workaround).

Fix. Exported detectDefault(opts?: { navLanguage?: string; storage?: Pick<Storage, "getItem"> | null; storageKey?: string }) and a DetectDefaultOptions interface. All fields are optional; omitted fields fall back to the ambient browser globals (globalThis.localStorage, navigator.language) exactly as before, so export const locale = signal<Locale>(detectDefault()) at the module top level behaves byte-for-byte identically in the browser. Tests and SSR hosts can now inject a Map-backed storage stub or an explicit navLanguage and drive both branches without touching global state.

Verification.

• New unit test file tests/unit/viewer/i18n-detect-default.test.ts covers 13 cases: injected zh/en saved values, ambient-global fallbacks, custom storageKey, throwing-storage fallback, case-insensitive zh-* matching, and precedence of injected options over ambient globals. All 13 pass (0 skipped).
• Full viewer test suite (12 files, 69 tests) passes; the pre-existing restart-copy.test.ts workaround still works unchanged.
• npm run lint (== tsc --noEmit) passes cleanly.
• Whole-repo baseline: the unrelated MemOS unit-test failures under tests/unit/memory/, tests/unit/storage/, etc. exist on dev-v2.0.30 before this change and are outside the scope of the plugin viewer fix — this commit adds 13 passing tests and introduces zero new failures.

Base branch: main
Branch: bugfix/autodev-2346-20260907141702290
Commit: 38a5931
PR: #2347
Assigned to: @wustzdy
Reviewers: @whipser030, @hijzy