ethers-rs/ethers-providers/src/pending_transaction.rs

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use crate::{JsonRpcClient, Provider, ProviderError};
use ethers_core::types::{TransactionReceipt, TxHash, U64};
use pin_project::pin_project;
use std::{
fmt,
future::Future,
ops::Deref,
pin::Pin,
task::{Context, Poll},
};
/// A pending transaction is a transaction which has been submitted but is not yet mined.
/// `await`'ing on a pending transaction will resolve to a transaction receipt
/// once the transaction has enough `confirmations`. The default number of confirmations
/// is 1, but may be adjusted with the `confirmations` method. If the transaction does not
/// have enough confirmations or is not mined, the future will stay in the pending state.
#[pin_project]
pub struct PendingTransaction<'a, P> {
tx_hash: TxHash,
confirmations: usize,
provider: &'a Provider<P>,
state: PendingTxState<'a>,
}
impl<'a, P: JsonRpcClient> PendingTransaction<'a, P> {
/// Creates a new pending transaction poller from a hash and a provider
pub fn new(tx_hash: TxHash, provider: &'a Provider<P>) -> Self {
let fut = Box::pin(provider.get_transaction_receipt(tx_hash));
Self {
tx_hash,
confirmations: 1,
provider,
state: PendingTxState::GettingReceipt(fut),
}
}
/// Sets the number of confirmations for the pending transaction to resolve
/// to a receipt
pub fn confirmations(mut self, confs: usize) -> Self {
self.confirmations = confs;
self
}
}
impl<'a, P: JsonRpcClient> Future for PendingTransaction<'a, P> {
type Output = Result<TransactionReceipt, ProviderError>;
fn poll(self: Pin<&mut Self>, ctx: &mut Context) -> Poll<Self::Output> {
let this = self.project();
match this.state {
PendingTxState::GettingReceipt(fut) => {
let receipt = futures_util::ready!(fut.as_mut().poll(ctx))?;
*this.state = PendingTxState::CheckingReceipt(Box::new(receipt))
}
PendingTxState::CheckingReceipt(receipt) => {
// If we requested more than 1 confirmation, we need to compare the receipt's
// block number and the current block
if *this.confirmations > 1 {
let fut = Box::pin(this.provider.get_block_number());
*this.state =
PendingTxState::GettingBlockNumber(fut, Box::new(*receipt.clone()))
} else {
let receipt = *receipt.clone();
*this.state = PendingTxState::Completed;
return Poll::Ready(Ok(receipt));
}
}
PendingTxState::GettingBlockNumber(fut, receipt) => {
let inclusion_block = receipt
.block_number
.expect("Receipt did not have a block number. This should never happen");
let current_block = futures_util::ready!(fut.as_mut().poll(ctx))?;
// if the transaction has at least K confirmations, return the receipt
// (subtract 1 since the tx already has 1 conf when it's mined)
if current_block >= inclusion_block + *this.confirmations - 1 {
let receipt = *receipt.clone();
*this.state = PendingTxState::Completed;
return Poll::Ready(Ok(receipt));
} else {
// we need to re-instantiate the get_block_number future so that
// we poll again
let fut = Box::pin(this.provider.get_block_number());
*this.state = PendingTxState::GettingBlockNumber(fut, receipt.clone());
return Poll::Pending;
}
}
PendingTxState::Completed => {
panic!("polled pending transaction future after completion")
}
};
Poll::Pending
}
}
impl<'a, P> fmt::Debug for PendingTransaction<'a, P> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("PendingTransaction")
.field("tx_hash", &self.tx_hash)
.field("confirmations", &self.confirmations)
.field("state", &self.state)
.finish()
}
}
impl<'a, P> PartialEq for PendingTransaction<'a, P> {
fn eq(&self, other: &Self) -> bool {
self.tx_hash == other.tx_hash
}
}
impl<'a, P> PartialEq<TxHash> for PendingTransaction<'a, P> {
fn eq(&self, other: &TxHash) -> bool {
&self.tx_hash == other
}
}
impl<'a, P> Eq for PendingTransaction<'a, P> {}
impl<'a, P> Deref for PendingTransaction<'a, P> {
type Target = TxHash;
fn deref(&self) -> &Self::Target {
&self.tx_hash
}
}
// Helper type alias
type PinBoxFut<'a, T> = Pin<Box<dyn Future<Output = Result<T, ProviderError>> + 'a>>;
// We box the TransactionReceipts to keep the enum small.
enum PendingTxState<'a> {
/// Polling the blockchain for the receipt
GettingReceipt(PinBoxFut<'a, TransactionReceipt>),
/// Polling the blockchain for the current block number
GettingBlockNumber(PinBoxFut<'a, U64>, Box<TransactionReceipt>),
/// If the pending tx required only 1 conf, it will return early. Otherwise it will
/// proceed to the next state which will poll the block number until there have been
/// enough confirmations
CheckingReceipt(Box<TransactionReceipt>),
/// Future has completed and should panic if polled again
Completed,
}
impl<'a> fmt::Debug for PendingTxState<'a> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let state = match self {
PendingTxState::GettingReceipt(_) => "GettingReceipt",
PendingTxState::GettingBlockNumber(_, _) => "GettingBlockNumber",
PendingTxState::CheckingReceipt(_) => "CheckingReceipt",
PendingTxState::Completed => "Completed",
};
f.debug_struct("PendingTxState")
.field("state", &state)
.finish()
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::Http;
use ethers_core::{types::TransactionRequest, utils::Ganache};
use std::convert::TryFrom;
#[tokio::test]
async fn test_pending_tx() {
let _ganache = Ganache::new().spawn();
let provider = Provider::<Http>::try_from("http://localhost:8545").unwrap();
let accounts = provider.get_accounts().await.unwrap();
let tx = TransactionRequest::pay(accounts[0], 1000).from(accounts[0]);
let pending_tx = provider.send_transaction(tx).await.unwrap();
let receipt = provider
.get_transaction_receipt(pending_tx.tx_hash)
.await
.unwrap();
// the pending tx resolves to the same receipt
let tx_receipt = pending_tx.confirmations(1).await.unwrap();
assert_eq!(receipt, tx_receipt);
}
}