library-api-design

Mark every public and internal function virtual, except alias functions and convenience overloads that only forward to a canonical virtual form. Use public rather than external for override points, since an override of an external function cannot call super.

Use memory for strings, bytes, arrays, and structs by default, including in public functions, because calldata forces every inheritor to match. Calldata is only valid for msg.data slices, narrowly scoped internal decoding helpers, or explicit Calldata-suffixed utility variants.

Make _mint, _burn, and _transfer non-virtual aliases that delegate to one virtual _update function. Extensions override only _update, call super._update first, then add side effects, keeping all state machine entry points consistent.

Prefer no-ops when doing nothing creates no security concern: skip vacuous inputs silently, return a bool for idempotent state transitions, and provide empty internal virtual hooks as extension points. Overrides can add requirements on top of a no-op base but cannot remove enforced ones.

ERC-7201 is opt-in, not the default, because upgradeable variants are auto-generated by the OpenZeppelin Transpiler. Use it only when namespacing is genuinely necessary, such as Initializable.sol, and always verify the slot with SlotDerivation.erc7201Slot().