An extension to the JavaScript Ethereum Provider API (EIP-1193) this creates a new message type in the event a transaction replacement occurs.
The current communication between providers and consumers of providers are fundamentally broken in the event that a transaction in the mempool has been superseded by a newer transactions. Providers currently have no way of communicating a transaction replacement, and consumers are required to poll block by block for the resulting transaction.
Exert from EIP-1193
A common convention in the Ethereum web application ("dapp") ecosystem is for key management software ("wallets") to expose their API via a JavaScript object in the web page. This object is called "the Provider".
Many ingenious developments have been made by wallet developers to improve the overall user experience while interacting with the Ethereum blockchain. One specific innovation was transaction replacement, offering users the ability to effectively cancel a previously sent transaction.
Transaction replacement is not a new concept, but unfortunately causes major user experience problems for dapp developers as the replaced transaction is near impossible to track.
This EIP formalizes a way for both providers and dapp developers to track transaction replacements seamlessly.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119.
This section is non-normative.
These methods MUST be implemented per the Node.js EventEmitter API.
The following three events must be implemented: tx_replacement, tx_speedup and tx_cancel.
A tx_speedup is defined as a transaction replacement in which the user wishes to adjust the gasPrice, to potentially receive a fast block inclusion. For a tx_speedup to be considered valid, the replacement tx must contain the same following properties as the one it supersedes:
This event emits the old transaction hash (oldTx), the new transaction hash (newTx), the nonce used for both transactions (nonce), and the signing address for the transaction (from).
A tx_cancel is defined as a transaction replacement in which the user wishes to nullify a previous transaction before its inclusion. For a tx_cancel to be considered valid, the replacement tx must contain the following properties:
This event emits the old transaction hash (oldTx), the new transaction hash (newTx), the nonce used for both transactions (nonce), and the signing address for the transaction (from).
A tx_replacement is defined as a transaction replacement in which a user has completely replaced a previous transaction with a completely brand new one. The replacement tx must contain the following properties:
This event emits the old transaction hash (oldTx), the new transaction hash (newTx), the nonce used for both transactions (nonce), and the signing address for the transaction (from).
The implementation was chosen to help the ease of implementation for both providers and dapp developers. Since ProviderMessage is widely used by dapp developers already it means that the implementation path would be as trivial as adding and additional if clause to their existing message listener. This also provides a benefit to dapps in the event that a provider has not yet implemented the events, it will not cause the dapp panic with undefined should it be implemented natively (eg: ethereum.txCancel(...) which would error with ethereum.txReplacement() is not a function).
Many Providers adopted EIP-1193, as this EIP extends the same event logic, there should be no breaking changes. All providers that do not support the new events should either I) Ignore the subscription or II) Provide some error to the user.
None at the current time.
Copyright and related rights waived via CC0.
These examples assume a web browser environment.