From 369c868f9b13faae12bb4ddca32d6c0a9946af10 Mon Sep 17 00:00:00 2001
From: Marius van der Wijden <m.vanderwijden@live.de>
Date: Mon, 7 Sep 2020 10:52:01 +0200
Subject: [PATCH] eth: added trace_call to trace on top of arbitrary blocks
 (#21338)

* eth: Added TraceTransactionPending

* eth: Implement Trace_Call, remove traceTxPending

* eth: debug_call -> debug_traceCall, recompute tx environment if pruned

* eth: fix nil panic

* eth: improve block retrieving logic in tracers

* internal/web3ext: add debug_traceCall to console
# Conflicts:
#	eth/api.go
#	eth/api_tracer.go
---
 eth/api.go                  |  5 +++++
 eth/api_tracer.go           | 38 +++++++++++++++++++++++++++++++++++++
 internal/web3ext/web3ext.go |  6 ++++++
 3 files changed, 49 insertions(+)

diff --git a/eth/api.go b/eth/api.go
index b8a2d12b4..ee66e9371 100644
--- a/eth/api.go
+++ b/eth/api.go
@@ -378,7 +378,12 @@ func (api *PublicDebugAPI) AccountRange(blockNrOrHash rpc.BlockNumberOrHash, sta
 
 // StorageRangeAt returns the storage at the given block height and transaction index.
 func (api *PrivateDebugAPI) StorageRangeAt(ctx context.Context, blockHash common.Hash, txIndex uint64, contractAddress common.Address, keyStart hexutil.Bytes, maxResult int) (StorageRangeResult, error) {
+	// Retrieve the block
 	_, _, _, dbstate, err := ComputeTxEnv(ctx, api.eth.blockchain, api.eth.blockchain.Config(), api.eth.blockchain, api.eth.ChainKV(), blockHash, txIndex)
+	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
 	}
diff --git a/eth/api_tracer.go b/eth/api_tracer.go
index e15c1d1b8..7acfb6bed 100644
--- a/eth/api_tracer.go
+++ b/eth/api_tracer.go
@@ -604,6 +604,10 @@ func (api *PrivateDebugAPI) TraceTransaction(ctx context.Context, hash common.Ha
 		return nil, fmt.Errorf("transaction %#x not found", hash)
 	}
 	msg, vmctx, statedb, _, err := ComputeTxEnv(ctx, api.eth.blockchain, api.eth.blockchain.Config(), api.eth.blockchain, api.eth.ChainKV(), blockHash, index)
+	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
 	}
@@ -611,6 +615,40 @@ func (api *PrivateDebugAPI) TraceTransaction(ctx context.Context, hash common.Ha
 	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.
diff --git a/internal/web3ext/web3ext.go b/internal/web3ext/web3ext.go
index 80ac92fe4..41d865778 100644
--- a/internal/web3ext/web3ext.go
+++ b/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',