[pi0x]

Closes #36.

Summary

TTL was fixed at creation time (maxAge / staleMaxAge). This adds a getMaxAge hook that derives an entry's lifetime from the value it resolved to, so the cache can honor per-entry expiry instead of a single global constant.

const getToken = defineCachedFunction(() => fetchToken(), {
  // cache each token for exactly its own lifetime (number shorthand for maxAge)
  getMaxAge: (entry) => entry.value?.expires_in,
});

Motivating cases: OAuth/API tokens with expires_in, upstream responses carrying their own Cache-Control: max-age, or content-derived freshness.

How it works

• getMaxAge?: (entry) => number | { maxAge?, staleMaxAge? } | undefined runs after the resolver, before the entry is persisted (async-supported).
• A bare number is shorthand for { maxAge }; return an object to also override the stale window.
• The resolved values are stored on the entry (CacheEntry.maxAge / CacheEntry.staleMaxAge) and used for both the read-side freshness check (including the SWR stale window) and the storage TTL on write.
• Missing field / undefined return → falls back to the static option. If the hook throws, the entry is still cached with static options and the error is reported via onError.
• expireCache() prefers the per-entry TTL when computing the remaining storage window.
• Flows through to defineCachedHandler automatically (entry value is the ResponseCacheEntry).

Compatibility

Additive and fully backwards compatible — when getMaxAge is absent, behavior is unchanged.

Tests

New getMaxAge block covering: number-shorthand freshness derived from the value, persistence on the stored entry, fallback when the hook returns undefined, per-entry SWR stale window, hook-throws resilience, and expireCache respecting per-entry TTL. All 105 tests pass; typecheck clean.

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Review details

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Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 1f53c43c-a4da-485d-a964-e068b6edd92b

📥 Commits

Reviewing files that changed from the base of the PR and between 0266ada and 4d042a2.

📒 Files selected for processing (5)

• AGENTS.md
• README.md
• src/cache.ts
• src/types.ts
• test/index.test.ts

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/dynamic-ttl

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