Troubleshooting¶

The Delayed Function Runs More Than Once¶

Need does not provide exactly-once synchronization. Concurrent callers can observe the same unevaluated computation and run duplicate work before the cached value converges.

Keep delayed functions pure or idempotent when sharing a Need across threads. Use an external synchronization primitive if a side effect must happen exactly once.

Equality or Logging Forces Work¶

Need.equals and Need.hashCode compare computed values, so they force evaluation. toString shows the current backing state and should be treated as diagnostic output, not a stable serialized format.

Avoid putting unevaluated Need instances in hash-based collections if evaluation is expensive or has side effects.

Nullable Values Are Not Cached by build¶

Need.build caches only non-null resolver results. A null result is returned to the caller but is not stored, so later lookups for the same key re-run the resolver.

Use buildNonNull when every key has a value that should be cached.

Recursive Values Do Not Terminate¶

Need.recursive permits self-referential definitions. It does not make non-terminating definitions productive. If forcing the result keeps asking for itself without reaching a base case, evaluation will not complete.