From ab2caaee1167a8bef9760d84b45716f1bddcc381 Mon Sep 17 00:00:00 2001
From: Martin Holst Swende <martin@swende.se>
Date: Tue, 28 Sep 2021 12:53:11 +0200
Subject: [PATCH] eth/tracers: implement debug.intermediateRoots (#23594)

This PR implements a new debug method, which I've talked briefly about to some other client developers. It allows the caller to obtain the intermediate state roots for a block (which might be either a canon block or a 'bad' block).
---
 eth/tracers/api.go          | 75 ++++++++++++++++++++++++++++++++-----
 internal/web3ext/web3ext.go |  6 +++
 2 files changed, 71 insertions(+), 10 deletions(-)

diff --git a/eth/tracers/api.go b/eth/tracers/api.go
index 68265932854c..39b95264d762 100644
--- a/eth/tracers/api.go
+++ b/eth/tracers/api.go
@@ -445,12 +445,11 @@ func (api *API) TraceBlockFromFile(ctx context.Context, file string, config *Tra
 // EVM against a block pulled from the pool of bad ones and returns them as a JSON
 // object.
 func (api *API) TraceBadBlock(ctx context.Context, hash common.Hash, config *TraceConfig) ([]*txTraceResult, error) {
-	for _, block := range rawdb.ReadAllBadBlocks(api.backend.ChainDb()) {
-		if block.Hash() == hash {
-			return api.traceBlock(ctx, block, config)
-		}
+	block := rawdb.ReadBadBlock(api.backend.ChainDb(), hash)
+	if block == nil {
+		return nil, fmt.Errorf("bad block %#x not found", hash)
 	}
-	return nil, fmt.Errorf("bad block %#x not found", hash)
+	return api.traceBlock(ctx, block, config)
 }
 
 // StandardTraceBlockToFile dumps the structured logs created during the
@@ -464,16 +463,72 @@ func (api *API) StandardTraceBlockToFile(ctx context.Context, hash common.Hash,
 	return api.standardTraceBlockToFile(ctx, block, config)
 }
 
+// IntermediateRoots executes a block (bad- or canon- or side-), and returns a list
+// of intermediate roots: the stateroot after each transaction.
+func (api *API) IntermediateRoots(ctx context.Context, hash common.Hash, config *TraceConfig) ([]common.Hash, error) {
+	block, _ := api.blockByHash(ctx, hash)
+	if block == nil {
+		// Check in the bad blocks
+		block = rawdb.ReadBadBlock(api.backend.ChainDb(), hash)
+	}
+	if block == nil {
+		return nil, fmt.Errorf("block %#x not found", hash)
+	}
+	if block.NumberU64() == 0 {
+		return nil, errors.New("genesis is not traceable")
+	}
+	parent, err := api.blockByNumberAndHash(ctx, rpc.BlockNumber(block.NumberU64()-1), block.ParentHash())
+	if err != nil {
+		return nil, err
+	}
+	reexec := defaultTraceReexec
+	if config != nil && config.Reexec != nil {
+		reexec = *config.Reexec
+	}
+	statedb, err := api.backend.StateAtBlock(ctx, parent, reexec, nil, true)
+	if err != nil {
+		return nil, err
+	}
+	var (
+		roots              []common.Hash
+		signer             = types.MakeSigner(api.backend.ChainConfig(), block.Number())
+		chainConfig        = api.backend.ChainConfig()
+		vmctx              = core.NewEVMBlockContext(block.Header(), api.chainContext(ctx), nil)
+		deleteEmptyObjects = chainConfig.IsEIP158(block.Number())
+	)
+	for i, tx := range block.Transactions() {
+		var (
+			msg, _    = tx.AsMessage(signer, block.BaseFee())
+			txContext = core.NewEVMTxContext(msg)
+			vmenv     = vm.NewEVM(vmctx, txContext, statedb, chainConfig, vm.Config{})
+		)
+		statedb.Prepare(tx.Hash(), i)
+		if _, err := core.ApplyMessage(vmenv, msg, new(core.GasPool).AddGas(msg.Gas())); err != nil {
+			log.Warn("Tracing intermediate roots did not complete", "txindex", i, "txhash", tx.Hash(), "err", err)
+			// We intentionally don't return the error here: if we do, then the RPC server will not
+			// return the roots. Most likely, the caller already knows that a certain transaction fails to
+			// be included, but still want the intermediate roots that led to that point.
+			// It may happen the tx_N causes an erroneous state, which in turn causes tx_N+M to not be
+			// executable.
+			// N.B: This should never happen while tracing canon blocks, only when tracing bad blocks.
+			return roots, nil
+		}
+		// calling IntermediateRoot will internally call Finalize on the state
+		// so any modifications are written to the trie
+		roots = append(roots, statedb.IntermediateRoot(deleteEmptyObjects))
+	}
+	return roots, nil
+}
+
 // StandardTraceBadBlockToFile dumps the structured logs created during the
 // execution of EVM against a block pulled from the pool of bad ones to the
 // local file system and returns a list of files to the caller.
 func (api *API) StandardTraceBadBlockToFile(ctx context.Context, hash common.Hash, config *StdTraceConfig) ([]string, error) {
-	for _, block := range rawdb.ReadAllBadBlocks(api.backend.ChainDb()) {
-		if block.Hash() == hash {
-			return api.standardTraceBlockToFile(ctx, block, config)
-		}
+	block := rawdb.ReadBadBlock(api.backend.ChainDb(), hash)
+	if block == nil {
+		return nil, fmt.Errorf("bad block %#x not found", hash)
 	}
-	return nil, fmt.Errorf("bad block %#x not found", hash)
+	return api.standardTraceBlockToFile(ctx, block, config)
 }
 
 // traceBlock configures a new tracer according to the provided configuration, and
diff --git a/internal/web3ext/web3ext.go b/internal/web3ext/web3ext.go
index fe15cb0509d3..ad459362a59b 100644
--- a/internal/web3ext/web3ext.go
+++ b/internal/web3ext/web3ext.go
@@ -391,6 +391,12 @@ web3._extend({
 			params: 2,
 			inputFormatter: [null, null]
 		}),
+		new web3._extend.Method({
+			name: 'intermediateRoots',
+			call: 'debug_intermediateRoots',
+			params: 2,
+			inputFormatter: [null, null]
+		}),
 		new web3._extend.Method({
 			name: 'standardTraceBlockToFile',
 			call: 'debug_standardTraceBlockToFile',