graphql, internal/ethapi: support overriding accounts in eth_call (#19917)

* graphql, internal/ethapi: extend eth_call

This PR offers the third option parameter for eth_call API.
Caller can specify a batch of contracts for overriding the
original account metadata(nonce, balance, code, state).
It has a few advantages:

* It's friendly for debugging
* It's can make on-chain contract lighter for getting rid of
  state access functions

* core, internal: address comments

4 files changed, 99 insertions, 8 deletions

diff --git a/core/state/state_object.go b/core/state/state_object.go
index 852c340b8..45ae95a2a 100644
--- a/core/state/state_object.go
+++ b/core/state/state_object.go
@@ -81,6 +81,7 @@ type stateObject struct {
 
 	originStorage Storage // Storage cache of original entries to dedup rewrites
 	dirtyStorage  Storage // Storage entries that need to be flushed to disk
+	fakeStorage   Storage // Fake storage which constructed by caller for debugging purpose.
 
 	// Cache flags.
 	// When an object is marked suicided it will be delete from the trie
@@ -163,6 +164,10 @@ func (s *stateObject) getTrie(db Database) Trie {
 
 // GetState retrieves a value from the account storage trie.
 func (s *stateObject) GetState(db Database, key common.Hash) common.Hash {
+	// If the fake storage is set, only lookup the state here(in the debugging mode)
+	if s.fakeStorage != nil {
+		return s.fakeStorage[key]
+	}
 	// If we have a dirty value for this state entry, return it
 	value, dirty := s.dirtyStorage[key]
 	if dirty {
@@ -174,12 +179,16 @@ func (s *stateObject) GetState(db Database, key common.Hash) common.Hash {
 
 // GetCommittedState retrieves a value from the committed account storage trie.
 func (s *stateObject) GetCommittedState(db Database, key common.Hash) common.Hash {
+	// If the fake storage is set, only lookup the state here(in the debugging mode)
+	if s.fakeStorage != nil {
+		return s.fakeStorage[key]
+	}
 	// If we have the original value cached, return that
 	value, cached := s.originStorage[key]
 	if cached {
 		return value
 	}
-	// Track the amount of time wasted on reading the storge trie
+	// Track the amount of time wasted on reading the storage trie
 	if metrics.EnabledExpensive {
 		defer func(start time.Time) { s.db.StorageReads += time.Since(start) }(time.Now())
 	}
@@ -202,6 +211,11 @@ func (s *stateObject) GetCommittedState(db Database, key common.Hash) common.Has
 
 // SetState updates a value in account storage.
 func (s *stateObject) SetState(db Database, key, value common.Hash) {
+	// If the fake storage is set, put the temporary state update here.
+	if s.fakeStorage != nil {
+		s.fakeStorage[key] = value
+		return
+	}
 	// If the new value is the same as old, don't set
 	prev := s.GetState(db, key)
 	if prev == value {
@@ -216,6 +230,24 @@ func (s *stateObject) SetState(db Database, key, value common.Hash) {
 	s.setState(key, value)
 }
 
+// SetStorage replaces the entire state storage with the given one.
+//
+// After this function is called, all original state will be ignored and state
+// lookup only happens in the fake state storage.
+//
+// Note this function should only be used for debugging purpose.
+func (s *stateObject) SetStorage(storage map[common.Hash]common.Hash) {
+	// Allocate fake storage if it's nil.
+	if s.fakeStorage == nil {
+		s.fakeStorage = make(Storage)
+	}
+	for key, value := range storage {
+		s.fakeStorage[key] = value
+	}
+	// Don't bother journal since this function should only be used for
+	// debugging and the `fake` storage won't be committed to database.
+}
+
 func (s *stateObject) setState(key, value common.Hash) {
 	s.dirtyStorage[key] = value
 }
diff --git a/core/state/statedb.go b/core/state/statedb.go
index 3bb9862ed..b07f08fd2 100644
--- a/core/state/statedb.go
+++ b/core/state/statedb.go
@@ -386,6 +386,15 @@ func (self *StateDB) SetState(addr common.Address, key, value common.Hash) {
 	}
 }
 
+// SetStorage replaces the entire storage for the specified account with given
+// storage. This function should only be used for debugging.
+func (self *StateDB) SetStorage(addr common.Address, storage map[common.Hash]common.Hash) {
+	stateObject := self.GetOrNewStateObject(addr)
+	if stateObject != nil {
+		stateObject.SetStorage(storage)
+	}
+}
+
 // Suicide marks the given account as suicided.
 // This clears the account balance.
 //
diff --git a/graphql/graphql.go b/graphql/graphql.go
index 771c3c62f..df279f42b 100644
--- a/graphql/graphql.go
+++ b/graphql/graphql.go
@@ -817,7 +817,7 @@ func (b *Block) Call(ctx context.Context, args struct {
 			return nil, err
 		}
 	}
-	result, gas, failed, err := ethapi.DoCall(ctx, b.backend, args.Data, *b.num, vm.Config{}, 5*time.Second, b.backend.RPCGasCap())
+	result, gas, failed, err := ethapi.DoCall(ctx, b.backend, args.Data, *b.num, nil, vm.Config{}, 5*time.Second, b.backend.RPCGasCap())
 	status := hexutil.Uint64(1)
 	if failed {
 		status = 0
@@ -885,7 +885,7 @@ func (p *Pending) Account(ctx context.Context, args struct {
 func (p *Pending) Call(ctx context.Context, args struct {
 	Data ethapi.CallArgs
 }) (*CallResult, error) {
-	result, gas, failed, err := ethapi.DoCall(ctx, p.backend, args.Data, rpc.PendingBlockNumber, vm.Config{}, 5*time.Second, p.backend.RPCGasCap())
+	result, gas, failed, err := ethapi.DoCall(ctx, p.backend, args.Data, rpc.PendingBlockNumber, nil, vm.Config{}, 5*time.Second, p.backend.RPCGasCap())
 	status := hexutil.Uint64(1)
 	if failed {
 		status = 0
diff --git a/internal/ethapi/api.go b/internal/ethapi/api.go
index b67017a90..05204e547 100644
--- a/internal/ethapi/api.go
+++ b/internal/ethapi/api.go
@@ -743,7 +743,21 @@ type CallArgs struct {
 	Data     *hexutil.Bytes  `json:"data"`
 }
 
-func DoCall(ctx context.Context, b Backend, args CallArgs, blockNr rpc.BlockNumber, vmCfg vm.Config, timeout time.Duration, globalGasCap *big.Int) ([]byte, uint64, bool, error) {
+// account indicates the overriding fields of account during the execution of
+// a message call.
+// Note, state and stateDiff can't be specified at the same time. If state is
+// set, message execution will only use the data in the given state. Otherwise
+// if statDiff is set, all diff will be applied first and then execute the call
+// message.
+type account struct {
+	Nonce     *hexutil.Uint64              `json:"nonce"`
+	Code      *hexutil.Bytes               `json:"code"`
+	Balance   **hexutil.Big                `json:"balance"`
+	State     *map[common.Hash]common.Hash `json:"state"`
+	StateDiff *map[common.Hash]common.Hash `json:"stateDiff"`
+}
+
+func DoCall(ctx context.Context, b Backend, args CallArgs, blockNr rpc.BlockNumber, overrides map[common.Address]account, vmCfg vm.Config, timeout time.Duration, globalGasCap *big.Int) ([]byte, uint64, bool, error) {
 	defer func(start time.Time) { log.Debug("Executing EVM call finished", "runtime", time.Since(start)) }(time.Now())
 
 	state, header, err := b.StateAndHeaderByNumber(ctx, blockNr)
@@ -761,6 +775,34 @@ func DoCall(ctx context.Context, b Backend, args CallArgs, blockNr rpc.BlockNumb
 	} else {
 		addr = *args.From
 	}
+	// Override the fields of specified contracts before execution.
+	for addr, account := range overrides {
+		// Override account nonce.
+		if account.Nonce != nil {
+			state.SetNonce(addr, uint64(*account.Nonce))
+		}
+		// Override account(contract) code.
+		if account.Code != nil {
+			state.SetCode(addr, *account.Code)
+		}
+		// Override account balance.
+		if account.Balance != nil {
+			state.SetBalance(addr, (*big.Int)(*account.Balance))
+		}
+		if account.State != nil && account.StateDiff != nil {
+			return nil, 0, false, fmt.Errorf("account %s has both 'state' and 'stateDiff'", addr.Hex())
+		}
+		// Replace entire state if caller requires.
+		if account.State != nil {
+			state.SetStorage(addr, *account.State)
+		}
+		// Apply state diff into specified accounts.
+		if account.StateDiff != nil {
+			for key, value := range *account.StateDiff {
+				state.SetState(addr, key, value)
+			}
+		}
+	}
 	// Set default gas & gas price if none were set
 	gas := uint64(math.MaxUint64 / 2)
 	if args.Gas != nil {
@@ -827,9 +869,17 @@ func DoCall(ctx context.Context, b Backend, args CallArgs, blockNr rpc.BlockNumb
 }
 
 // Call executes the given transaction on the state for the given block number.
-// It doesn't make and changes in the state/blockchain and is useful to execute and retrieve values.
-func (s *PublicBlockChainAPI) Call(ctx context.Context, args CallArgs, blockNr rpc.BlockNumber) (hexutil.Bytes, error) {
-	result, _, _, err := DoCall(ctx, s.b, args, blockNr, vm.Config{}, 5*time.Second, s.b.RPCGasCap())
+//
+// Additionally, the caller can specify a batch of contract for fields overriding.
+//
+// Note, this function doesn't make and changes in the state/blockchain and is
+// useful to execute and retrieve values.
+func (s *PublicBlockChainAPI) Call(ctx context.Context, args CallArgs, blockNr rpc.BlockNumber, overrides *map[common.Address]account) (hexutil.Bytes, error) {
+	var accounts map[common.Address]account
+	if overrides != nil {
+		accounts = *overrides
+	}
+	result, _, _, err := DoCall(ctx, s.b, args, blockNr, accounts, vm.Config{}, 5*time.Second, s.b.RPCGasCap())
 	return (hexutil.Bytes)(result), err
 }
 
@@ -860,7 +910,7 @@ func DoEstimateGas(ctx context.Context, b Backend, args CallArgs, blockNr rpc.Bl
 	executable := func(gas uint64) bool {
 		args.Gas = (*hexutil.Uint64)(&gas)
 
-		_, _, failed, err := DoCall(ctx, b, args, rpc.PendingBlockNumber, vm.Config{}, 0, gasCap)
+		_, _, failed, err := DoCall(ctx, b, args, rpc.PendingBlockNumber, nil, vm.Config{}, 0, gasCap)
 		if err != nil || failed {
 			return false
 		}