fix: only invalidate cache tags when mutation response body reports success (#1162)

[wendyamoni-creator]

Summary

Fixes #1162 — cache tags were being invalidated for any POST/DELETE that returned HTTP 2xx, regardless of whether the response body's success field indicated a business-logic failure.

Root Cause

The invalidation block in request() fired unconditionally on every 2xx mutation response:

// before
if (method === "POST" || method === "DELETE") {
  if (options.cacheTags?.length) {
    apiCache.invalidateByTags(options.cacheTags);
  } else {
    apiCache.invalidateByPattern('.*');
  }
}

newsletterSubscribe and newsletterUnsubscribe both carry [CacheTag.NEWSLETTER, CacheTag.STATISTICS] tags and can return { success: false, message: '...' } with HTTP 200. A rejected subscription was therefore busting the statistics cache, triggering an unnecessary refetch and a brief stale flicker for unrelated cached data.

Fix

// after — guard invalidation behind the response body's success field
if (method === "POST" || method === "DELETE") {
  const bodyObj = (typeof data === 'object' && data !== null)
    ? data as Record<string, unknown>
    : null;
  const succeeded =
    bodyObj === null ||
    !('success' in bodyObj) ||
    bodyObj['success'] === true;
  if (succeeded) {
    if (options.cacheTags?.length) {
      apiCache.invalidateByTags(options.cacheTags);
    } else {
      apiCache.invalidateByPattern('.*');
    }
  }
}

Rules:

• No success field → treat as success (non-envelope endpoints like resolveMarket)
• success: true → invalidate as before
• success: false → skip invalidation entirely

Tests

Added 3 new tests to the Cache invalidation strategy suite in client.test.ts:

1. success:false — 200 response with { success: false } does NOT invalidate cache
2. success:true — 200 response with { success: true } DOES invalidate cache
3. no success field — 200 response without success key DOES invalidate cache (non-envelope endpoint)

Checklist

• Branch named fix/cache-tags-are-invalidated-even-when-a-mutation
• cd frontend && npm test -- client — 52 tests, 1 suite, all passed
• cd frontend && npm run build — compiled successfully, 0 warnings closes [Bug] Cache tags are invalidated even when a mutation's response body reports business-logic failure #1162

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