accounts/abi/bind/backends: add simulated reorgs (#22624)

* accounts/abi/bind/backends: add blockByHashNoLock

Signed-off-by: Oliver Tale-Yazdi <oliver@perun.network>

* accounts/abi/bind/backends: add 'parent' arg to rollback

Signed-off-by: Oliver Tale-Yazdi <oliver@perun.network>

* accounts/abi/bind/backends: add simulated forks

Signed-off-by: Oliver Tale-Yazdi <oliver@perun.network>

* accounts/abi/bind/backends: minor nitpicks

* accounts/abi/bind/backends: don't add defensive panics

Co-authored-by: Péter Szilágyi <peterke@gmail.com>

accounts/abi/bind/backends/simulated.go

@@ -86,7 +86,7 @@ func NewSimulatedBackendWithDatabase(database ethdb.Database, alloc core.Genesis
 		config:     genesis.Config,
 		events:     filters.NewEventSystem(&filterBackend{database, blockchain}, false),
 	}
-	backend.rollback()
+	backend.rollback(blockchain.CurrentBlock())
 	return backend
 }
 
@@ -112,7 +112,9 @@ func (b *SimulatedBackend) Commit() {
 	if _, err := b.blockchain.InsertChain([]*types.Block{b.pendingBlock}); err != nil {
 		panic(err) // This cannot happen unless the simulator is wrong, fail in that case
 	}
-	b.rollback()
+	// Using the last inserted block here makes it possible to build on a side
+	// chain after a fork.
+	b.rollback(b.pendingBlock)
 }
 
 // Rollback aborts all pending transactions, reverting to the last committed state.
@@ -120,22 +122,49 @@ func (b *SimulatedBackend) Rollback() {
 	b.mu.Lock()
 	defer b.mu.Unlock()
 
-	b.rollback()
+	b.rollback(b.blockchain.CurrentBlock())
 }
 
-func (b *SimulatedBackend) rollback() {
+func (b *SimulatedBackend) rollback(parent *types.Block) {
-	blocks, _ := core.GenerateChain(b.config, b.blockchain.CurrentBlock(), ethash.NewFaker(), b.database, 1, func(int, *core.BlockGen) {})
+	blocks, _ := core.GenerateChain(b.config, parent, ethash.NewFaker(), b.database, 1, func(int, *core.BlockGen) {})
 
 	b.pendingBlock = blocks[0]
 	b.pendingState, _ = state.New(b.pendingBlock.Root(), b.blockchain.StateCache(), nil)
 }
 
+// Fork creates a side-chain that can be used to simulate reorgs.
+//
+// This function should be called with the ancestor block where the new side
+// chain should be started. Transactions (old and new) can then be applied on
+// top and Commit-ed.
+//
+// Note, the side-chain will only become canonical (and trigger the events) when
+// it becomes longer. Until then CallContract will still operate on the current
+// canonical chain.
+//
+// There is a % chance that the side chain becomes canonical at the same length
+// to simulate live network behavior.
+func (b *SimulatedBackend) Fork(ctx context.Context, parent common.Hash) error {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	if len(b.pendingBlock.Transactions()) != 0 {
+		return errors.New("pending block dirty")
+	}
+	block, err := b.blockByHash(ctx, parent)
+	if err != nil {
+		return err
+	}
+	b.rollback(block)
+	return nil
+}
+
 // stateByBlockNumber retrieves a state by a given blocknumber.
 func (b *SimulatedBackend) stateByBlockNumber(ctx context.Context, blockNumber *big.Int) (*state.StateDB, error) {
 	if blockNumber == nil || blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) == 0 {
 		return b.blockchain.State()
 	}
-	block, err := b.blockByNumberNoLock(ctx, blockNumber)
+	block, err := b.blockByNumber(ctx, blockNumber)
 	if err != nil {
 		return nil, err
 	}
@@ -228,6 +257,11 @@ func (b *SimulatedBackend) BlockByHash(ctx context.Context, hash common.Hash) (*
 	b.mu.Lock()
 	defer b.mu.Unlock()
 
+	return b.blockByHash(ctx, hash)
+}
+
+// blockByHash retrieves a block based on the block hash without Locking.
+func (b *SimulatedBackend) blockByHash(ctx context.Context, hash common.Hash) (*types.Block, error) {
 	if hash == b.pendingBlock.Hash() {
 		return b.pendingBlock, nil
 	}
@@ -246,12 +280,12 @@ func (b *SimulatedBackend) BlockByNumber(ctx context.Context, number *big.Int) (
 	b.mu.Lock()
 	defer b.mu.Unlock()
 
-	return b.blockByNumberNoLock(ctx, number)
+	return b.blockByNumber(ctx, number)
 }
 
-// blockByNumberNoLock retrieves a block from the database by number, caching it
+// blockByNumber retrieves a block from the database by number, caching it
 // (associated with its hash) if found without Lock.
-func (b *SimulatedBackend) blockByNumberNoLock(ctx context.Context, number *big.Int) (*types.Block, error) {
+func (b *SimulatedBackend) blockByNumber(ctx context.Context, number *big.Int) (*types.Block, error) {
 	if number == nil || number.Cmp(b.pendingBlock.Number()) == 0 {
 		return b.blockchain.CurrentBlock(), nil
 	}
@@ -559,8 +593,12 @@ func (b *SimulatedBackend) SendTransaction(ctx context.Context, tx *types.Transa
 	b.mu.Lock()
 	defer b.mu.Unlock()
 
-	// Check transaction validity.
+	// Get the last block
-	block := b.blockchain.CurrentBlock()
+	block, err := b.blockByHash(ctx, b.pendingBlock.ParentHash())
+	if err != nil {
+		panic("could not fetch parent")
+	}
+	// Check transaction validity
 	signer := types.MakeSigner(b.blockchain.Config(), block.Number())
 	sender, err := types.Sender(signer, tx)
 	if err != nil {
@@ -570,8 +608,7 @@ func (b *SimulatedBackend) SendTransaction(ctx context.Context, tx *types.Transa
 	if tx.Nonce() != nonce {
 		panic(fmt.Errorf("invalid transaction nonce: got %d, want %d", tx.Nonce(), nonce))
 	}
-
+	// Include tx in chain
-	// Include tx in chain.
 	blocks, _ := core.GenerateChain(b.config, block, ethash.NewFaker(), b.database, 1, func(number int, block *core.BlockGen) {
 		for _, tx := range b.pendingBlock.Transactions() {
 			block.AddTxWithChain(b.blockchain, tx)

accounts/abi/bind/backends/simulated_test.go

@@ -21,6 +21,7 @@ import (
 	"context"
 	"errors"
 	"math/big"
+	"math/rand"
 	"reflect"
 	"strings"
 	"testing"
@@ -136,7 +137,7 @@ func TestNewSimulatedBackend(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_AdjustTime(t *testing.T) {
+func TestAdjustTime(t *testing.T) {
 	sim := NewSimulatedBackend(
 		core.GenesisAlloc{}, 10000000,
 	)
@@ -153,7 +154,7 @@ func TestSimulatedBackend_AdjustTime(t *testing.T) {
 	}
 }
 
-func TestNewSimulatedBackend_AdjustTimeFail(t *testing.T) {
+func TestNewAdjustTimeFail(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 	sim := simTestBackend(testAddr)
 	// Create tx and send
@@ -191,7 +192,7 @@ func TestNewSimulatedBackend_AdjustTimeFail(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_BalanceAt(t *testing.T) {
+func TestBalanceAt(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 	expectedBal := big.NewInt(10000000000)
 	sim := simTestBackend(testAddr)
@@ -208,7 +209,7 @@ func TestSimulatedBackend_BalanceAt(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_BlockByHash(t *testing.T) {
+func TestBlockByHash(t *testing.T) {
 	sim := NewSimulatedBackend(
 		core.GenesisAlloc{}, 10000000,
 	)
@@ -229,7 +230,7 @@ func TestSimulatedBackend_BlockByHash(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_BlockByNumber(t *testing.T) {
+func TestBlockByNumber(t *testing.T) {
 	sim := NewSimulatedBackend(
 		core.GenesisAlloc{}, 10000000,
 	)
@@ -264,7 +265,7 @@ func TestSimulatedBackend_BlockByNumber(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_NonceAt(t *testing.T) {
+func TestNonceAt(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 
 	sim := simTestBackend(testAddr)
@@ -314,7 +315,7 @@ func TestSimulatedBackend_NonceAt(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_SendTransaction(t *testing.T) {
+func TestSendTransaction(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 
 	sim := simTestBackend(testAddr)
@@ -345,7 +346,7 @@ func TestSimulatedBackend_SendTransaction(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_TransactionByHash(t *testing.T) {
+func TestTransactionByHash(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 
 	sim := NewSimulatedBackend(
@@ -396,7 +397,7 @@ func TestSimulatedBackend_TransactionByHash(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_EstimateGas(t *testing.T) {
+func TestEstimateGas(t *testing.T) {
 	/*
 		pragma solidity ^0.6.4;
 		contract GasEstimation {
@@ -514,7 +515,7 @@ func TestSimulatedBackend_EstimateGas(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_EstimateGasWithPrice(t *testing.T) {
+func TestEstimateGasWithPrice(t *testing.T) {
 	key, _ := crypto.GenerateKey()
 	addr := crypto.PubkeyToAddress(key.PublicKey)
 
@@ -581,7 +582,7 @@ func TestSimulatedBackend_EstimateGasWithPrice(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_HeaderByHash(t *testing.T) {
+func TestHeaderByHash(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 
 	sim := simTestBackend(testAddr)
@@ -602,7 +603,7 @@ func TestSimulatedBackend_HeaderByHash(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_HeaderByNumber(t *testing.T) {
+func TestHeaderByNumber(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 
 	sim := simTestBackend(testAddr)
@@ -649,7 +650,7 @@ func TestSimulatedBackend_HeaderByNumber(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_TransactionCount(t *testing.T) {
+func TestTransactionCount(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 
 	sim := simTestBackend(testAddr)
@@ -699,7 +700,7 @@ func TestSimulatedBackend_TransactionCount(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_TransactionInBlock(t *testing.T) {
+func TestTransactionInBlock(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 
 	sim := simTestBackend(testAddr)
@@ -762,7 +763,7 @@ func TestSimulatedBackend_TransactionInBlock(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_PendingNonceAt(t *testing.T) {
+func TestPendingNonceAt(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 
 	sim := simTestBackend(testAddr)
@@ -824,7 +825,7 @@ func TestSimulatedBackend_PendingNonceAt(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_TransactionReceipt(t *testing.T) {
+func TestTransactionReceipt(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 
 	sim := simTestBackend(testAddr)
@@ -855,7 +856,7 @@ func TestSimulatedBackend_TransactionReceipt(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_SuggestGasPrice(t *testing.T) {
+func TestSuggestGasPrice(t *testing.T) {
 	sim := NewSimulatedBackend(
 		core.GenesisAlloc{},
 		10000000,
@@ -871,7 +872,7 @@ func TestSimulatedBackend_SuggestGasPrice(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_PendingCodeAt(t *testing.T) {
+func TestPendingCodeAt(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 	sim := simTestBackend(testAddr)
 	defer sim.Close()
@@ -907,7 +908,7 @@ func TestSimulatedBackend_PendingCodeAt(t *testing.T) {
 	}
 }
 
-func TestSimulatedBackend_CodeAt(t *testing.T) {
+func TestCodeAt(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 	sim := simTestBackend(testAddr)
 	defer sim.Close()
@@ -946,7 +947,7 @@ func TestSimulatedBackend_CodeAt(t *testing.T) {
 
 // When receive("X") is called with sender 0x00... and value 1, it produces this tx receipt:
 //   receipt{status=1 cgas=23949 bloom=00000000004000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000040200000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 logs=[log: b6818c8064f645cd82d99b59a1a267d6d61117ef [75fd880d39c1daf53b6547ab6cb59451fc6452d27caa90e5b6649dd8293b9eed] 000000000000000000000000376c47978271565f56deb45495afa69e59c16ab200000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000060000000000000000000000000000000000000000000000000000000000000000158 9ae378b6d4409eada347a5dc0c180f186cb62dc68fcc0f043425eb917335aa28 0 95d429d309bb9d753954195fe2d69bd140b4ae731b9b5b605c34323de162cf00 0]}
-func TestSimulatedBackend_PendingAndCallContract(t *testing.T) {
+func TestPendingAndCallContract(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 	sim := simTestBackend(testAddr)
 	defer sim.Close()
@@ -1030,7 +1031,7 @@ contract Reverter {
         }
     }
 }*/
-func TestSimulatedBackend_CallContractRevert(t *testing.T) {
+func TestCallContractRevert(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 	sim := simTestBackend(testAddr)
 	defer sim.Close()
@@ -1114,3 +1115,172 @@ func TestSimulatedBackend_CallContractRevert(t *testing.T) {
 		sim.Commit()
 	}
 }
+
+// TestFork check that the chain length after a reorg is correct.
+// Steps:
+//  1. Save the current block which will serve as parent for the fork.
+//  2. Mine n blocks with n ∈ [0, 20].
+//  3. Assert that the chain length is n.
+//  4. Fork by using the parent block as ancestor.
+//  5. Mine n+1 blocks which should trigger a reorg.
+//  6. Assert that the chain length is n+1.
+//     Since Commit() was called 2n+1 times in total,
+//     having a chain length of just n+1 means that a reorg occurred.
+func TestFork(t *testing.T) {
+	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
+	sim := simTestBackend(testAddr)
+	defer sim.Close()
+	// 1.
+	parent := sim.blockchain.CurrentBlock()
+	// 2.
+	n := int(rand.Int31n(21))
+	for i := 0; i < n; i++ {
+		sim.Commit()
+	}
+	// 3.
+	if sim.blockchain.CurrentBlock().NumberU64() != uint64(n) {
+		t.Error("wrong chain length")
+	}
+	// 4.
+	sim.Fork(context.Background(), parent.Hash())
+	// 5.
+	for i := 0; i < n+1; i++ {
+		sim.Commit()
+	}
+	// 6.
+	if sim.blockchain.CurrentBlock().NumberU64() != uint64(n+1) {
+		t.Error("wrong chain length")
+	}
+}
+
+/*
+Example contract to test event emission:
+
+pragma solidity >=0.7.0 <0.9.0;
+contract Callable {
+    event Called();
+    function Call() public { emit Called(); }
+}
+*/
+const callableAbi = "[{\"anonymous\":false,\"inputs\":[],\"name\":\"Called\",\"type\":\"event\"},{\"inputs\":[],\"name\":\"Call\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"}]"
+
+const callableBin = "6080604052348015600f57600080fd5b5060998061001e6000396000f3fe6080604052348015600f57600080fd5b506004361060285760003560e01c806334e2292114602d575b600080fd5b60336035565b005b7f81fab7a4a0aa961db47eefc81f143a5220e8c8495260dd65b1356f1d19d3c7b860405160405180910390a156fea2646970667358221220029436d24f3ac598ceca41d4d712e13ced6d70727f4cdc580667de66d2f51d8b64736f6c63430008010033"
+
+// TestForkLogsReborn check that the simulated reorgs
+// correctly remove and reborn logs.
+// Steps:
+//  1. Deploy the Callable contract.
+//  2. Set up an event subscription.
+//  3. Save the current block which will serve as parent for the fork.
+//  4. Send a transaction.
+//  5. Check that the event was included.
+//  6. Fork by using the parent block as ancestor.
+//  7. Mine two blocks to trigger a reorg.
+//  8. Check that the event was removed.
+//  9. Re-send the transaction and mine a block.
+// 10. Check that the event was reborn.
+func TestForkLogsReborn(t *testing.T) {
+	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
+	sim := simTestBackend(testAddr)
+	defer sim.Close()
+	// 1.
+	parsed, _ := abi.JSON(strings.NewReader(callableAbi))
+	auth, _ := bind.NewKeyedTransactorWithChainID(testKey, big.NewInt(1337))
+	_, _, contract, err := bind.DeployContract(auth, parsed, common.FromHex(callableBin), sim)
+	if err != nil {
+		t.Errorf("deploying contract: %v", err)
+	}
+	sim.Commit()
+	// 2.
+	logs, sub, err := contract.WatchLogs(nil, "Called")
+	if err != nil {
+		t.Errorf("watching logs: %v", err)
+	}
+	defer sub.Unsubscribe()
+	// 3.
+	parent := sim.blockchain.CurrentBlock()
+	// 4.
+	tx, err := contract.Transact(auth, "Call")
+	if err != nil {
+		t.Errorf("transacting: %v", err)
+	}
+	sim.Commit()
+	// 5.
+	log := <-logs
+	if log.TxHash != tx.Hash() {
+		t.Error("wrong event tx hash")
+	}
+	if log.Removed {
+		t.Error("Event should be included")
+	}
+	// 6.
+	if err := sim.Fork(context.Background(), parent.Hash()); err != nil {
+		t.Errorf("forking: %v", err)
+	}
+	// 7.
+	sim.Commit()
+	sim.Commit()
+	// 8.
+	log = <-logs
+	if log.TxHash != tx.Hash() {
+		t.Error("wrong event tx hash")
+	}
+	if !log.Removed {
+		t.Error("Event should be removed")
+	}
+	// 9.
+	if err := sim.SendTransaction(context.Background(), tx); err != nil {
+		t.Errorf("sending transaction: %v", err)
+	}
+	sim.Commit()
+	// 10.
+	log = <-logs
+	if log.TxHash != tx.Hash() {
+		t.Error("wrong event tx hash")
+	}
+	if log.Removed {
+		t.Error("Event should be included")
+	}
+}
+
+// TestForkResendTx checks that re-sending a TX after a fork
+// is possible and does not cause a "nonce mismatch" panic.
+// Steps:
+//  1. Save the current block which will serve as parent for the fork.
+//  2. Send a transaction.
+//  3. Check that the TX is included in block 1.
+//  4. Fork by using the parent block as ancestor.
+//  5. Mine a block, Re-send the transaction and mine another one.
+//  6. Check that the TX is now included in block 2.
+func TestForkResendTx(t *testing.T) {
+	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
+	sim := simTestBackend(testAddr)
+	defer sim.Close()
+	// 1.
+	parent := sim.blockchain.CurrentBlock()
+	// 2.
+	_tx := types.NewTransaction(0, testAddr, big.NewInt(1000), params.TxGas, big.NewInt(1), nil)
+	tx, _ := types.SignTx(_tx, types.HomesteadSigner{}, testKey)
+	sim.SendTransaction(context.Background(), tx)
+	sim.Commit()
+	// 3.
+	receipt, _ := sim.TransactionReceipt(context.Background(), tx.Hash())
+	if h := receipt.BlockNumber.Uint64(); h != 1 {
+		t.Errorf("TX included in wrong block: %d", h)
+	}
+	// 4.
+	if err := sim.Fork(context.Background(), parent.Hash()); err != nil {
+		t.Errorf("forking: %v", err)
+	}
+	// 5.
+	sim.Commit()
+	if err := sim.SendTransaction(context.Background(), tx); err != nil {
+		t.Errorf("sending transaction: %v", err)
+	}
+	sim.Commit()
+	// 6.
+	receipt, _ = sim.TransactionReceipt(context.Background(), tx.Hash())
+	if h := receipt.BlockNumber.Uint64(); h != 2 {
+		t.Errorf("TX included in wrong block: %d", h)
+	}
+}