Add optional validate guard to loadFromStorage + tests

[codegen-sh]

Requested by: Jake Ruesink

Summary

• Add optional runtime validation to packages/utils/src/storage.ts loadFromStorage<T> so parsed values can be gated by a provided type guard.
• Behavior: if validate is provided and returns false, return fallback instead of trusting JSON.parse blindly.
• No breaking changes to existing callers (third param optional).

Changes

• Update signature and implementation of loadFromStorage to accept validate?: (value: unknown) => value is T and apply it to the parsed value.
• Add unit tests in packages/utils/src/__tests__/storage.test.ts covering:
  • valid parse path
  • malformed JSON fallback path
  • validate-guard reject path

Integration notes

• Optional callsite updates can pass a guard function when desired, e.g., for the TodoState shape in apps/todo-app/app/lib/todo-context.tsx. Current behavior remains unchanged if omitted.

Relevant files

• packages/utils/src/storage.ts
• packages/utils/src/tests/storage.test.ts

Compliance

• Repo rules: created changes on a feature branch, validated with lint and typecheck at workspace level, and added tests (utils package tests pass).

---

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[linear]

STA-7 [Major] Add runtime validation to storage loader (utils.loadFromStorage)

Requested by: Jake Ruesink

Summary
Add an optional runtime validation step to the storage loader so we never trust JSON.parse blindly. This prevents invalid shapes from poisoning app state and improves robustness.

Base branch for PR: codegen-bot/persist-todos-localstorage-STA-2-1754688724
Target repo: lambda-curry/react-router-starter

Code context

• File: packages/utils/src/storage.ts
• Current:

export function loadFromStorage<T>(key: string, fallback: T): T {
  const storage = getStorage();
  if (!storage) return fallback;
  try {
    const raw = storage.getItem(key);
    if (!raw) return fallback;
    return JSON.parse(raw) as T; // broad cast
  } catch {
    return fallback;
  }
}

• Change signature and gate parsed value with a type guard:

export function loadFromStorage<T>(
  key: string,
  fallback: T,
  validate?: (value: unknown) => value is T
): T {
  const storage = getStorage();
  if (!storage) return fallback;
  try {
    const raw = storage.getItem(key);
    if (!raw) return fallback;
    const parsed = JSON.parse(raw);
    if (validate && !validate(parsed)) return fallback;
    return parsed as T;
  } catch {
    return fallback;
  }
}

• Optional call site update (no behavior change if omitted):
  • File: apps/todo-app/app/lib/todo-context.tsx
  • Provide a simple guard for TodoState (object with todos array and filter string), or keep current behavior by not passing validate.

Acceptance criteria

• loadFromStorage accepts an optional validate guard and returns fallback when validation fails.
• No breaking changes to existing callers; all current usage continues to work.
• Unit tests cover: valid parse, malformed JSON fallback, validate-guard reject path.

References

• PR Persist todos in localStorage + minimal storage utils (STA-2) #7: Persist todos in localStorage + minimal storage utils (STA-2) #7 (review item 1)

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[codegen-sh]

🔍 Check Suite Status for PR #11

Check	Status	Commit	Time	Check Suite	Agent trace
quality-checks	🔄 Working	4b16a9a	Just now	Run	Agent Work

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