Module extension 

Scarcity transaction extension.

Runtime ordering

AsScarcity changes a signed origin into Origin::Nft during validation. Following Coinage’s purse model, runtime integrators must place it with the origin modifiers, before frame_system::AuthorizeCall, signed-account checks, and transaction payment:

AsScarcity -> AuthorizeCall -> ... -> CheckNonce -> ... ->
    SkipCheckIfFeeless<ChargeAssetTxPayment>

The account checks deliberately see a non-system origin and skip it, so an NFT-only purse needs neither a System account nor a balance. AsScarcity consumes the NFT during preparation to prevent concurrent use. A successful move increments its state nonce. Failed dispatch restores the same state and applies a temporary backoff lock; once that lock expires, the same signed transaction can be submitted again. This is the same retry model as Coinage.

Placing this extension after payment prevents pallet_skip_feeless_payment::SkipCheckIfFeeless from observing Origin::Nft and makes a balance-less purse unable to transact.

Replay and mortality

Purse authorization is not account-nonce-based: a signed NFT transaction stays valid for as long as its purse still holds the named instance at the named state nonce. Two rules bound stale intent, exactly as in Coinage:

• Callers must sign mortal transactions with an era shorter than Config::LockPeriod. A successful move invalidates every outstanding authorization by incrementing the state nonce, but an unexecuted transaction is otherwise replayable by anyone who has seen it until its era expires.
• Because the era ends before the shortest failure lock does, a failed transaction can never re-enter a block: every retry after a failure is a fresh signing decision rather than a third-party replay of the old transaction.

A holder can also cancel an outstanding authorization at any time by moving the NFT, which increments its state nonce.

Structs

AsScarcity

Purse-key authorization for Scarcity transfers and burns.

Enums

AsScarcityInfo

The Scarcity authorization requested by this extension.

CustomInvalidity

An error reported while validating AsScarcity.

Pre

Information carried from preparation to post-dispatch.

Val

Information carried from validation to preparation.