eth: added trace_call to trace on top of arbitrary blocks

eth/api.go

@@ -412,7 +412,12 @@ type storageEntry struct {
 
 // StorageRangeAt returns the storage at the given block height and transaction index.
 func (api *PrivateDebugAPI) StorageRangeAt(blockHash common.Hash, txIndex int, contractAddress common.Address, keyStart hexutil.Bytes, maxResult int) (StorageRangeResult, error) {
-	_, _, statedb, err := api.computeTxEnv(blockHash, txIndex, 0)
+	// Retrieve the block
+	block := api.eth.blockchain.GetBlockByHash(blockHash)
+	if block == nil {
+		return StorageRangeResult{}, fmt.Errorf("block %#x not found", blockHash)
+	}
+	_, _, statedb, err := api.computeTxEnv(block, txIndex, 0)
 	if err != nil {
 		return StorageRangeResult{}, err
 	}

eth/api_tracer.go

@@ -711,14 +711,53 @@ func (api *PrivateDebugAPI) TraceTransaction(ctx context.Context, hash common.Ha
 	if config != nil && config.Reexec != nil {
 		reexec = *config.Reexec
 	}
-	msg, vmctx, statedb, err := api.computeTxEnv(blockHash, int(index), reexec)
+	// Retrieve the block
+	block := api.eth.blockchain.GetBlockByHash(blockHash)
+	if block == nil {
+		return nil, fmt.Errorf("block %#x not found", blockHash)
+	}
+	msg, vmctx, statedb, err := api.computeTxEnv(block, int(index), reexec)
 	if err != nil {
 		return nil, err
 	}
 	// Trace the transaction and return
 	return api.traceTx(ctx, msg, vmctx, statedb, config)
 }
 
+// TraceCall lets you trace a given eth_call. It collects the structured logs created during the execution of EVM
+// if the given transaction was added on top of the provided block and returns them as a JSON object.
+// You can provide -2 as a block number to trace on top of the pending block.
+func (api *PrivateDebugAPI) TraceCall(ctx context.Context, args ethapi.CallArgs, blockNrOrHash rpc.BlockNumberOrHash, config *TraceConfig) (interface{}, error) {
+	// First try to retrieve the state
+	statedb, header, err := api.eth.APIBackend.StateAndHeaderByNumberOrHash(ctx, blockNrOrHash)
+	if err != nil {
+		// Try to retrieve the specified block
+		var block *types.Block
+		if hash, ok := blockNrOrHash.Hash(); ok {
+			block = api.eth.blockchain.GetBlockByHash(hash)
+		} else if number, ok := blockNrOrHash.Number(); ok {
+			block = api.eth.blockchain.GetBlockByNumber(uint64(number))
+		}
+		if block == nil {
+			return nil, fmt.Errorf("block %v not found: %v", blockNrOrHash, err)
+		}
+		// try to recompute the state
+		reexec := defaultTraceReexec
+		if config != nil && config.Reexec != nil {
+			reexec = *config.Reexec
+		}
+		_, _, statedb, err = api.computeTxEnv(block, 0, reexec)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	// Execute the trace
+	msg := args.ToMessage(api.eth.APIBackend.RPCGasCap())
+	vmctx := core.NewEVMContext(msg, header, api.eth.blockchain, nil)
+	return api.traceTx(ctx, msg, vmctx, statedb, config)
+}
+
 // traceTx configures a new tracer according to the provided configuration, and
 // executes the given message in the provided environment. The return value will
 // be tracer dependent.
@@ -786,12 +825,8 @@ func (api *PrivateDebugAPI) traceTx(ctx context.Context, message core.Message, v
 }
 
 // computeTxEnv returns the execution environment of a certain transaction.
-func (api *PrivateDebugAPI) computeTxEnv(blockHash common.Hash, txIndex int, reexec uint64) (core.Message, vm.Context, *state.StateDB, error) {
+func (api *PrivateDebugAPI) computeTxEnv(block *types.Block, txIndex int, reexec uint64) (core.Message, vm.Context, *state.StateDB, error) {
 	// Create the parent state database
-	block := api.eth.blockchain.GetBlockByHash(blockHash)
-	if block == nil {
-		return nil, vm.Context{}, nil, fmt.Errorf("block %#x not found", blockHash)
-	}
 	parent := api.eth.blockchain.GetBlock(block.ParentHash(), block.NumberU64()-1)
 	if parent == nil {
 		return nil, vm.Context{}, nil, fmt.Errorf("parent %#x not found", block.ParentHash())
@@ -824,5 +859,5 @@ func (api *PrivateDebugAPI) computeTxEnv(blockHash common.Hash, txIndex int, ree
 		// Only delete empty objects if EIP158/161 (a.k.a Spurious Dragon) is in effect
 		statedb.Finalise(vmenv.ChainConfig().IsEIP158(block.Number()))
 	}
-	return nil, vm.Context{}, nil, fmt.Errorf("transaction index %d out of range for block %#x", txIndex, blockHash)
+	return nil, vm.Context{}, nil, fmt.Errorf("transaction index %d out of range for block %#x", txIndex, block.Hash())
 }

internal/web3ext/web3ext.go

@@ -429,6 +429,12 @@ web3._extend({
 			params: 2,
 			inputFormatter: [null, null]
 		}),
+		new web3._extend.Method({
+			name: 'traceCall',
+			call: 'debug_traceCall',
+			params: 3,
+			inputFormatter: [null, null, null]
+		}),
 		new web3._extend.Method({
 			name: 'preimage',
 			call: 'debug_preimage',