Merge pull request #705 from 0xProject/feature/revert-trace-subprovider

Introduce subprovider for printing revert stack traces

14 files changed, 365 insertions, 103 deletions

diff --git a/packages/contracts/package.json b/packages/contracts/package.json
index d6ca3727b..2495795dc 100644
--- a/packages/contracts/package.json
+++ b/packages/contracts/package.json
@@ -19,6 +19,7 @@
         "rebuild_and_test": "run-s build test",
         "test:coverage": "SOLIDITY_COVERAGE=true run-s build run_mocha coverage:report:text coverage:report:lcov",
         "test:profiler": "SOLIDITY_PROFILER=true run-s build run_mocha profiler:report:html",
+        "test:trace": "SOLIDITY_REVERT_TRACE=true run-s build run_mocha",
         "run_mocha": "mocha --require source-map-support/register 'lib/test/**/*.js' --timeout 100000 --bail --exit",
         "compile": "sol-compiler",
         "clean": "shx rm -rf lib src/generated_contract_wrappers",
diff --git a/packages/contracts/src/utils/revert_trace.ts b/packages/contracts/src/utils/revert_trace.ts
new file mode 100644
index 000000000..0bf8384bc
--- /dev/null
+++ b/packages/contracts/src/utils/revert_trace.ts
@@ -0,0 +1,21 @@
+import { devConstants } from '@0xproject/dev-utils';
+import { RevertTraceSubprovider, SolCompilerArtifactAdapter } from '@0xproject/sol-cov';
+import * as _ from 'lodash';
+
+let revertTraceSubprovider: RevertTraceSubprovider;
+
+export const revertTrace = {
+    getRevertTraceSubproviderSingleton(): RevertTraceSubprovider {
+        if (_.isUndefined(revertTraceSubprovider)) {
+            revertTraceSubprovider = revertTrace._getRevertTraceSubprovider();
+        }
+        return revertTraceSubprovider;
+    },
+    _getRevertTraceSubprovider(): RevertTraceSubprovider {
+        const defaultFromAddress = devConstants.TESTRPC_FIRST_ADDRESS;
+        const solCompilerArtifactAdapter = new SolCompilerArtifactAdapter();
+        const isVerbose = true;
+        const subprovider = new RevertTraceSubprovider(solCompilerArtifactAdapter, defaultFromAddress, isVerbose);
+        return subprovider;
+    },
+};
diff --git a/packages/contracts/src/utils/web3_wrapper.ts b/packages/contracts/src/utils/web3_wrapper.ts
index c475d96a9..c9d83a02d 100644
--- a/packages/contracts/src/utils/web3_wrapper.ts
+++ b/packages/contracts/src/utils/web3_wrapper.ts
@@ -2,9 +2,11 @@ import { devConstants, env, EnvVars, web3Factory } from '@0xproject/dev-utils';
 import { prependSubprovider } from '@0xproject/subproviders';
 import { logUtils } from '@0xproject/utils';
 import { Web3Wrapper } from '@0xproject/web3-wrapper';
+import * as _ from 'lodash';
 
 import { coverage } from './coverage';
 import { profiler } from './profiler';
+import { revertTrace } from './revert_trace';
 
 enum ProviderType {
     Ganache = 'ganache',
@@ -48,10 +50,11 @@ const providerConfigs = testProvider === ProviderType.Ganache ? ganacheConfigs :
 export const provider = web3Factory.getRpcProvider(providerConfigs);
 const isCoverageEnabled = env.parseBoolean(EnvVars.SolidityCoverage);
 const isProfilerEnabled = env.parseBoolean(EnvVars.SolidityProfiler);
-if (isCoverageEnabled && isProfilerEnabled) {
-    throw new Error(
-        `Unfortunately for now you can't enable both coverage and profiler at the same time. They both use coverage.json file and there is no way to configure that.`,
-    );
+const isRevertTraceEnabled = env.parseBoolean(EnvVars.SolidityRevertTrace);
+const enabledSubproviderCount = _.filter([isCoverageEnabled, isProfilerEnabled, isRevertTraceEnabled], _.identity)
+    .length;
+if (enabledSubproviderCount > 1) {
+    throw new Error(`Only one of coverage, profiler, or revert trace subproviders can be enabled at a time`);
 }
 if (isCoverageEnabled) {
     const coverageSubprovider = coverage.getCoverageSubproviderSingleton();
@@ -71,5 +74,9 @@ if (isProfilerEnabled) {
     profilerSubprovider.stop();
     prependSubprovider(provider, profilerSubprovider);
 }
+if (isRevertTraceEnabled) {
+    const revertTraceSubprovider = revertTrace.getRevertTraceSubproviderSingleton();
+    prependSubprovider(provider, revertTraceSubprovider);
+}
 
 export const web3Wrapper = new Web3Wrapper(provider);
diff --git a/packages/dev-utils/src/env.ts b/packages/dev-utils/src/env.ts
index e74ef3d23..024162c2f 100644
--- a/packages/dev-utils/src/env.ts
+++ b/packages/dev-utils/src/env.ts
@@ -4,6 +4,7 @@ import * as process from 'process';
 export enum EnvVars {
     SolidityCoverage = 'SOLIDITY_COVERAGE',
     SolidityProfiler = 'SOLIDITY_PROFILER',
+    SolidityRevertTrace = 'SOLIDITY_REVERT_TRACE',
     VerboseGanache = 'VERBOSE_GANACHE',
 }
 
diff --git a/packages/sol-cov/src/coverage_subprovider.ts b/packages/sol-cov/src/coverage_subprovider.ts
index 0fa7f873e..065a48434 100644
--- a/packages/sol-cov/src/coverage_subprovider.ts
+++ b/packages/sol-cov/src/coverage_subprovider.ts
@@ -2,8 +2,8 @@ import * as _ from 'lodash';
 
 import { AbstractArtifactAdapter } from './artifact_adapters/abstract_artifact_adapter';
 import { collectCoverageEntries } from './collect_coverage_entries';
-import { TraceCollectionSubprovider } from './trace_collection_subprovider';
 import { SingleFileSubtraceHandler, TraceCollector } from './trace_collector';
+import { TraceInfoSubprovider } from './trace_info_subprovider';
 import {
     BranchCoverage,
     ContractData,
@@ -22,7 +22,7 @@ import { utils } from './utils';
  * This class implements the [web3-provider-engine](https://github.com/MetaMask/provider-engine) subprovider interface.
  * It's used to compute your code coverage while running solidity tests.
  */
-export class CoverageSubprovider extends TraceCollectionSubprovider {
+export class CoverageSubprovider extends TraceInfoSubprovider {
     private _coverageCollector: TraceCollector;
     /**
      * Instantiates a CoverageSubprovider instance
@@ -39,7 +39,7 @@ export class CoverageSubprovider extends TraceCollectionSubprovider {
         super(defaultFromAddress, traceCollectionSubproviderConfig);
         this._coverageCollector = new TraceCollector(artifactAdapter, isVerbose, coverageHandler);
     }
-    public async handleTraceInfoAsync(traceInfo: TraceInfo): Promise<void> {
+    protected async _handleTraceInfoAsync(traceInfo: TraceInfo): Promise<void> {
         await this._coverageCollector.computeSingleTraceCoverageAsync(traceInfo);
     }
     /**
diff --git a/packages/sol-cov/src/index.ts b/packages/sol-cov/src/index.ts
index 10f6d9597..003a27374 100644
--- a/packages/sol-cov/src/index.ts
+++ b/packages/sol-cov/src/index.ts
@@ -1,6 +1,7 @@
 export { CoverageSubprovider } from './coverage_subprovider';
 // HACK: ProfilerSubprovider is a hacky way to do profiling using coverage tools. Not production ready
 export { ProfilerSubprovider } from './profiler_subprovider';
+export { RevertTraceSubprovider } from './revert_trace_subprovider';
 export { SolCompilerArtifactAdapter } from './artifact_adapters/sol_compiler_artifact_adapter';
 export { TruffleArtifactAdapter } from './artifact_adapters/truffle_artifact_adapter';
 export { AbstractArtifactAdapter } from './artifact_adapters/abstract_artifact_adapter';
diff --git a/packages/sol-cov/src/profiler_subprovider.ts b/packages/sol-cov/src/profiler_subprovider.ts
index 62ed1b472..9f98da524 100644
--- a/packages/sol-cov/src/profiler_subprovider.ts
+++ b/packages/sol-cov/src/profiler_subprovider.ts
@@ -2,8 +2,8 @@ import * as _ from 'lodash';
 
 import { AbstractArtifactAdapter } from './artifact_adapters/abstract_artifact_adapter';
 import { collectCoverageEntries } from './collect_coverage_entries';
-import { TraceCollectionSubprovider } from './trace_collection_subprovider';
 import { SingleFileSubtraceHandler, TraceCollector } from './trace_collector';
+import { TraceInfoSubprovider } from './trace_info_subprovider';
 import { ContractData, Coverage, SourceRange, Subtrace, TraceInfo } from './types';
 import { utils } from './utils';
 
@@ -11,7 +11,7 @@ import { utils } from './utils';
  * This class implements the [web3-provider-engine](https://github.com/MetaMask/provider-engine) subprovider interface.
  * ProfilerSubprovider is used to profile Solidity code while running tests.
  */
-export class ProfilerSubprovider extends TraceCollectionSubprovider {
+export class ProfilerSubprovider extends TraceInfoSubprovider {
     private _profilerCollector: TraceCollector;
     /**
      * Instantiates a ProfilerSubprovider instance
@@ -28,7 +28,7 @@ export class ProfilerSubprovider extends TraceCollectionSubprovider {
         super(defaultFromAddress, traceCollectionSubproviderConfig);
         this._profilerCollector = new TraceCollector(artifactAdapter, isVerbose, profilerHandler);
     }
-    public async handleTraceInfoAsync(traceInfo: TraceInfo): Promise<void> {
+    protected async _handleTraceInfoAsync(traceInfo: TraceInfo): Promise<void> {
         await this._profilerCollector.computeSingleTraceCoverageAsync(traceInfo);
     }
     /**
diff --git a/packages/sol-cov/src/revert_trace.ts b/packages/sol-cov/src/revert_trace.ts
new file mode 100644
index 000000000..a78d1afa8
--- /dev/null
+++ b/packages/sol-cov/src/revert_trace.ts
@@ -0,0 +1,90 @@
+import { logUtils } from '@0xproject/utils';
+import { OpCode, StructLog } from 'ethereum-types';
+
+import * as _ from 'lodash';
+
+import { EvmCallStack } from './types';
+import { utils } from './utils';
+
+export function getRevertTrace(structLogs: StructLog[], startAddress: string): EvmCallStack {
+    const evmCallStack: EvmCallStack = [];
+    const addressStack = [startAddress];
+    if (_.isEmpty(structLogs)) {
+        return [];
+    }
+    const normalizedStructLogs = utils.normalizeStructLogs(structLogs);
+    // tslint:disable-next-line:prefer-for-of
+    for (let i = 0; i < normalizedStructLogs.length; i++) {
+        const structLog = normalizedStructLogs[i];
+        if (structLog.depth !== addressStack.length - 1) {
+            throw new Error("Malformed trace. Trace depth doesn't match call stack depth");
+        }
+        // After that check we have a guarantee that call stack is never empty
+        // If it would: callStack.length - 1 === structLog.depth === -1
+        // That means that we can always safely pop from it
+
+        if (utils.isCallLike(structLog.op)) {
+            const currentAddress = _.last(addressStack) as string;
+            const jumpAddressOffset = 1;
+            const newAddress = utils.getAddressFromStackEntry(
+                structLog.stack[structLog.stack.length - jumpAddressOffset - 1],
+            );
+
+            // Sometimes calls don't change the execution context (current address). When we do a transfer to an
+            // externally owned account - it does the call and immediately returns because there is no fallback
+            // function. We manually check if the call depth had changed to handle that case.
+            const nextStructLog = normalizedStructLogs[i + 1];
+            if (nextStructLog.depth !== structLog.depth) {
+                addressStack.push(newAddress);
+                evmCallStack.push({
+                    address: currentAddress,
+                    structLog,
+                });
+            }
+        } else if (utils.isEndOpcode(structLog.op) && structLog.op !== OpCode.Revert) {
+            // Just like with calls, sometimes returns/stops don't change the execution context (current address).
+            const nextStructLog = normalizedStructLogs[i + 1];
+            if (_.isUndefined(nextStructLog) || nextStructLog.depth !== structLog.depth) {
+                evmCallStack.pop();
+                addressStack.pop();
+            }
+            if (structLog.op === OpCode.SelfDestruct) {
+                // After contract execution, we look at all sub-calls to external contracts, and for each one, fetch
+                // the bytecode and compute the coverage for the call. If the contract is destroyed with a call
+                // to `selfdestruct`, we are unable to fetch it's bytecode and compute coverage.
+                // TODO: Refactor this logic to fetch the sub-called contract bytecode before the selfdestruct is called
+                // in order to handle this edge-case.
+                logUtils.warn(
+                    "Detected a selfdestruct. Sol-cov currently doesn't support that scenario. We'll just skip the trace part for a destructed contract",
+                );
+            }
+        } else if (structLog.op === OpCode.Revert) {
+            evmCallStack.push({
+                address: _.last(addressStack) as string,
+                structLog,
+            });
+            return evmCallStack;
+        } else if (structLog.op === OpCode.Create) {
+            // TODO: Extract the new contract address from the stack and handle that scenario
+            logUtils.warn(
+                "Detected a contract created from within another contract. Sol-cov currently doesn't support that scenario. We'll just skip that trace",
+            );
+            return [];
+        } else {
+            if (structLog !== _.last(normalizedStructLogs)) {
+                const nextStructLog = normalizedStructLogs[i + 1];
+                if (nextStructLog.depth === structLog.depth) {
+                    continue;
+                } else if (nextStructLog.depth === structLog.depth - 1) {
+                    addressStack.pop();
+                } else {
+                    throw new Error('Malformed trace. Unexpected call depth change');
+                }
+            }
+        }
+    }
+    if (evmCallStack.length !== 0) {
+        logUtils.warn('Malformed trace. Call stack non empty at the end. (probably out of gas)');
+    }
+    return [];
+}
diff --git a/packages/sol-cov/src/revert_trace_subprovider.ts b/packages/sol-cov/src/revert_trace_subprovider.ts
new file mode 100644
index 000000000..b1d4da10c
--- /dev/null
+++ b/packages/sol-cov/src/revert_trace_subprovider.ts
@@ -0,0 +1,114 @@
+import { stripHexPrefix } from 'ethereumjs-util';
+import * as _ from 'lodash';
+import { getLogger, levels, Logger } from 'loglevel';
+
+import { AbstractArtifactAdapter } from './artifact_adapters/abstract_artifact_adapter';
+import { constants } from './constants';
+import { getRevertTrace } from './revert_trace';
+import { parseSourceMap } from './source_maps';
+import { TraceCollectionSubprovider } from './trace_collection_subprovider';
+import { ContractData, EvmCallStack, SourceRange } from './types';
+import { utils } from './utils';
+
+/**
+ * This class implements the [web3-provider-engine](https://github.com/MetaMask/provider-engine) subprovider interface.
+ * It is used to report call stack traces whenever a revert occurs.
+ */
+export class RevertTraceSubprovider extends TraceCollectionSubprovider {
+    // Lock is used to not accept normal transactions while doing call/snapshot magic because they'll be reverted later otherwise
+    private _contractsData!: ContractData[];
+    private _artifactAdapter: AbstractArtifactAdapter;
+    private _logger: Logger;
+
+    /**
+     * Instantiates a RevertTraceSubprovider instance
+     * @param artifactAdapter Adapter for used artifacts format (0x, truffle, giveth, etc.)
+     * @param defaultFromAddress default from address to use when sending transactions
+     * @param isVerbose If true, we will log any unknown transactions. Otherwise we will ignore them
+     */
+    constructor(artifactAdapter: AbstractArtifactAdapter, defaultFromAddress: string, isVerbose: boolean = true) {
+        const traceCollectionSubproviderConfig = {
+            shouldCollectTransactionTraces: true,
+            shouldCollectGasEstimateTraces: true,
+            shouldCollectCallTraces: true,
+        };
+        super(defaultFromAddress, traceCollectionSubproviderConfig);
+        this._artifactAdapter = artifactAdapter;
+        this._logger = getLogger('sol-cov');
+        this._logger.setLevel(isVerbose ? levels.TRACE : levels.ERROR);
+    }
+    // tslint:disable-next-line:no-unused-variable
+    protected async _recordTxTraceAsync(address: string, data: string | undefined, txHash: string): Promise<void> {
+        await this._web3Wrapper.awaitTransactionMinedAsync(txHash, 0);
+        const trace = await this._web3Wrapper.getTransactionTraceAsync(txHash, {
+            disableMemory: true,
+            disableStack: false,
+            disableStorage: true,
+        });
+        const evmCallStack = getRevertTrace(trace.structLogs, address);
+        if (evmCallStack.length > 0) {
+            // if getRevertTrace returns a call stack it means there was a
+            // revert.
+            await this._printStackTraceAsync(evmCallStack);
+        }
+    }
+    private async _printStackTraceAsync(evmCallStack: EvmCallStack): Promise<void> {
+        const sourceRanges: SourceRange[] = [];
+        if (_.isUndefined(this._contractsData)) {
+            this._contractsData = await this._artifactAdapter.collectContractsDataAsync();
+        }
+        for (const evmCallStackEntry of evmCallStack) {
+            const isContractCreation = evmCallStackEntry.address === constants.NEW_CONTRACT;
+            if (isContractCreation) {
+                this._logger.error('Contract creation not supported');
+                continue;
+            }
+            const bytecode = await this._web3Wrapper.getContractCodeAsync(evmCallStackEntry.address);
+            const contractData = utils.getContractDataIfExists(this._contractsData, bytecode);
+            if (_.isUndefined(contractData)) {
+                const errMsg = isContractCreation
+                    ? `Unknown contract creation transaction`
+                    : `Transaction to an unknown address: ${evmCallStackEntry.address}`;
+                this._logger.warn(errMsg);
+                continue;
+            }
+            const bytecodeHex = stripHexPrefix(bytecode);
+            const sourceMap = isContractCreation ? contractData.sourceMap : contractData.sourceMapRuntime;
+            const pcToSourceRange = parseSourceMap(
+                contractData.sourceCodes,
+                sourceMap,
+                bytecodeHex,
+                contractData.sources,
+            );
+            // tslint:disable-next-line:no-unnecessary-initializer
+            let sourceRange: SourceRange | undefined = undefined;
+            let pc = evmCallStackEntry.structLog.pc;
+            // Sometimes there is not a mapping for this pc (e.g. if the revert
+            // actually happens in assembly). In that case, we want to keep
+            // searching backwards by decrementing the pc until we find a
+            // mapped source range.
+            while (_.isUndefined(sourceRange)) {
+                sourceRange = pcToSourceRange[pc];
+                pc -= 1;
+                if (pc <= 0) {
+                    this._logger.warn(
+                        `could not find matching sourceRange for structLog: ${evmCallStackEntry.structLog}`,
+                    );
+                    continue;
+                }
+            }
+            sourceRanges.push(sourceRange);
+        }
+        if (sourceRanges.length > 0) {
+            this._logger.error('\n\nStack trace for REVERT:\n');
+            _.forEach(_.reverse(sourceRanges), sourceRange => {
+                this._logger.error(
+                    `${sourceRange.fileName}:${sourceRange.location.start.line}:${sourceRange.location.start.column}`,
+                );
+            });
+            this._logger.error('\n');
+        } else {
+            this._logger.error('Could not determine stack trace');
+        }
+    }
+}
diff --git a/packages/sol-cov/src/trace.ts b/packages/sol-cov/src/trace.ts
index 45e45e9c5..635019fc0 100644
--- a/packages/sol-cov/src/trace.ts
+++ b/packages/sol-cov/src/trace.ts
@@ -1,32 +1,25 @@
-import { addressUtils, BigNumber, logUtils } from '@0xproject/utils';
+import { logUtils } from '@0xproject/utils';
 import { OpCode, StructLog } from 'ethereum-types';
-import { addHexPrefix } from 'ethereumjs-util';
 import * as _ from 'lodash';
 
+import { utils } from './utils';
+
 export interface TraceByContractAddress {
     [contractAddress: string]: StructLog[];
 }
 
-function getAddressFromStackEntry(stackEntry: string): string {
-    const hexBase = 16;
-    return addressUtils.padZeros(new BigNumber(addHexPrefix(stackEntry)).toString(hexBase));
-}
-
 export function getTracesByContractAddress(structLogs: StructLog[], startAddress: string): TraceByContractAddress {
     const traceByContractAddress: TraceByContractAddress = {};
     let currentTraceSegment = [];
-    const callStack = [startAddress];
+    const addressStack = [startAddress];
     if (_.isEmpty(structLogs)) {
         return traceByContractAddress;
     }
-    if (structLogs[0].depth === 1) {
-        // Geth uses 1-indexed depth counter whilst ganache starts from 0
-        _.forEach(structLogs, structLog => structLog.depth--);
-    }
+    const normalizedStructLogs = utils.normalizeStructLogs(structLogs);
     // tslint:disable-next-line:prefer-for-of
-    for (let i = 0; i < structLogs.length; i++) {
-        const structLog = structLogs[i];
-        if (structLog.depth !== callStack.length - 1) {
+    for (let i = 0; i < normalizedStructLogs.length; i++) {
+        const structLog = normalizedStructLogs[i];
+        if (structLog.depth !== addressStack.length - 1) {
             throw new Error("Malformed trace. Trace depth doesn't match call stack depth");
         }
         // After that check we have a guarantee that call stack is never empty
@@ -34,36 +27,26 @@ export function getTracesByContractAddress(structLogs: StructLog[], startAddress
         // That means that we can always safely pop from it
         currentTraceSegment.push(structLog);
 
-        const isCallLike = _.includes(
-            [OpCode.CallCode, OpCode.StaticCall, OpCode.Call, OpCode.DelegateCall],
-            structLog.op,
-        );
-        const isEndOpcode = _.includes(
-            [OpCode.Return, OpCode.Stop, OpCode.Revert, OpCode.Invalid, OpCode.SelfDestruct],
-            structLog.op,
-        );
-        if (isCallLike) {
-            const currentAddress = _.last(callStack) as string;
+        if (utils.isCallLike(structLog.op)) {
+            const currentAddress = _.last(addressStack) as string;
             const jumpAddressOffset = 1;
-            const newAddress = getAddressFromStackEntry(
+            const newAddress = utils.getAddressFromStackEntry(
                 structLog.stack[structLog.stack.length - jumpAddressOffset - 1],
             );
-            if (structLog === _.last(structLogs)) {
-                throw new Error('Malformed trace. CALL-like opcode can not be the last one');
-            }
+
             // Sometimes calls don't change the execution context (current address). When we do a transfer to an
             // externally owned account - it does the call and immediately returns because there is no fallback
             // function. We manually check if the call depth had changed to handle that case.
-            const nextStructLog = structLogs[i + 1];
+            const nextStructLog = normalizedStructLogs[i + 1];
             if (nextStructLog.depth !== structLog.depth) {
-                callStack.push(newAddress);
+                addressStack.push(newAddress);
                 traceByContractAddress[currentAddress] = (traceByContractAddress[currentAddress] || []).concat(
                     currentTraceSegment,
                 );
                 currentTraceSegment = [];
             }
-        } else if (isEndOpcode) {
-            const currentAddress = callStack.pop() as string;
+        } else if (utils.isEndOpcode(structLog.op)) {
+            const currentAddress = addressStack.pop() as string;
             traceByContractAddress[currentAddress] = (traceByContractAddress[currentAddress] || []).concat(
                 currentTraceSegment,
             );
@@ -85,12 +68,12 @@ export function getTracesByContractAddress(structLogs: StructLog[], startAddress
             );
             return traceByContractAddress;
         } else {
-            if (structLog !== _.last(structLogs)) {
-                const nextStructLog = structLogs[i + 1];
+            if (structLog !== _.last(normalizedStructLogs)) {
+                const nextStructLog = normalizedStructLogs[i + 1];
                 if (nextStructLog.depth === structLog.depth) {
                     continue;
                 } else if (nextStructLog.depth === structLog.depth - 1) {
-                    const currentAddress = callStack.pop() as string;
+                    const currentAddress = addressStack.pop() as string;
                     traceByContractAddress[currentAddress] = (traceByContractAddress[currentAddress] || []).concat(
                         currentTraceSegment,
                     );
@@ -101,11 +84,11 @@ export function getTracesByContractAddress(structLogs: StructLog[], startAddress
             }
         }
     }
-    if (callStack.length !== 0) {
+    if (addressStack.length !== 0) {
         logUtils.warn('Malformed trace. Call stack non empty at the end');
     }
     if (currentTraceSegment.length !== 0) {
-        const currentAddress = callStack.pop() as string;
+        const currentAddress = addressStack.pop() as string;
         traceByContractAddress[currentAddress] = (traceByContractAddress[currentAddress] || []).concat(
             currentTraceSegment,
         );
diff --git a/packages/sol-cov/src/trace_collection_subprovider.ts b/packages/sol-cov/src/trace_collection_subprovider.ts
index 742735935..9866472b9 100644
--- a/packages/sol-cov/src/trace_collection_subprovider.ts
+++ b/packages/sol-cov/src/trace_collection_subprovider.ts
@@ -6,8 +6,7 @@ import * as _ from 'lodash';
 import { Lock } from 'semaphore-async-await';
 
 import { constants } from './constants';
-import { getTracesByContractAddress } from './trace';
-import { BlockParamLiteral, TraceInfo, TraceInfoExistingContract, TraceInfoNewContract } from './types';
+import { BlockParamLiteral } from './types';
 
 interface MaybeFakeTxData extends TxData {
     isFakeTransaction?: boolean;
@@ -27,13 +26,14 @@ export interface TraceCollectionSubproviderConfig {
 
 /**
  * This class implements the [web3-provider-engine](https://github.com/MetaMask/provider-engine) subprovider interface.
- * It collects traces of all transactions that were sent and all calls that were executed through JSON RPC.
+ * It collects traces of all transactions that were sent and all calls that were executed through JSON RPC. It must
+ * be extended by implementing the _recordTxTraceAsync method which is called for every transaction.
  */
 export abstract class TraceCollectionSubprovider extends Subprovider {
+    protected _web3Wrapper!: Web3Wrapper;
     // Lock is used to not accept normal transactions while doing call/snapshot magic because they'll be reverted later otherwise
     private _lock = new Lock();
     private _defaultFromAddress: string;
-    private _web3Wrapper!: Web3Wrapper;
     private _isEnabled = true;
     private _config: TraceCollectionSubproviderConfig;
     /**
@@ -58,11 +58,6 @@ export abstract class TraceCollectionSubprovider extends Subprovider {
         this._isEnabled = false;
     }
     /**
-     * Called for each subtrace.
-     * @param traceInfo Trace info for this subtrace.
-     */
-    public abstract handleTraceInfoAsync(traceInfo: TraceInfo): Promise<void>;
-    /**
      * This method conforms to the web3-provider-engine interface.
      * It is called internally by the ProviderEngine when it is this subproviders
      * turn to handle a JSON RPC request.
@@ -119,6 +114,11 @@ export abstract class TraceCollectionSubprovider extends Subprovider {
         super.setEngine(engine);
         this._web3Wrapper = new Web3Wrapper(engine);
     }
+    protected abstract async _recordTxTraceAsync(
+        address: string,
+        data: string | undefined,
+        txHash: string,
+    ): Promise<void>;
     private async _onTransactionSentAsync(
         txData: MaybeFakeTxData,
         err: Error | null,
@@ -160,52 +160,6 @@ export abstract class TraceCollectionSubprovider extends Subprovider {
         await this._recordCallOrGasEstimateTraceAsync(callData);
         cb();
     }
-    private async _recordTxTraceAsync(address: string, data: string | undefined, txHash: string): Promise<void> {
-        await this._web3Wrapper.awaitTransactionMinedAsync(txHash, 0);
-        const trace = await this._web3Wrapper.getTransactionTraceAsync(txHash, {
-            disableMemory: true,
-            disableStack: false,
-            disableStorage: true,
-        });
-        const tracesByContractAddress = getTracesByContractAddress(trace.structLogs, address);
-        const subcallAddresses = _.keys(tracesByContractAddress);
-        if (address === constants.NEW_CONTRACT) {
-            for (const subcallAddress of subcallAddresses) {
-                let traceInfo: TraceInfoNewContract | TraceInfoExistingContract;
-                if (subcallAddress === 'NEW_CONTRACT') {
-                    const traceForThatSubcall = tracesByContractAddress[subcallAddress];
-                    traceInfo = {
-                        subtrace: traceForThatSubcall,
-                        txHash,
-                        address: subcallAddress,
-                        bytecode: data as string,
-                    };
-                } else {
-                    const runtimeBytecode = await this._web3Wrapper.getContractCodeAsync(subcallAddress);
-                    const traceForThatSubcall = tracesByContractAddress[subcallAddress];
-                    traceInfo = {
-                        subtrace: traceForThatSubcall,
-                        txHash,
-                        address: subcallAddress,
-                        runtimeBytecode,
-                    };
-                }
-                await this.handleTraceInfoAsync(traceInfo);
-            }
-        } else {
-            for (const subcallAddress of subcallAddresses) {
-                const runtimeBytecode = await this._web3Wrapper.getContractCodeAsync(subcallAddress);
-                const traceForThatSubcall = tracesByContractAddress[subcallAddress];
-                const traceInfo: TraceInfoExistingContract = {
-                    subtrace: traceForThatSubcall,
-                    txHash,
-                    address: subcallAddress,
-                    runtimeBytecode,
-                };
-                await this.handleTraceInfoAsync(traceInfo);
-            }
-        }
-    }
     private async _recordCallOrGasEstimateTraceAsync(callData: Partial<CallData>): Promise<void> {
         // We don't want other transactions to be exeucted during snashotting period, that's why we lock the
         // transaction execution for all transactions except our fake ones.
diff --git a/packages/sol-cov/src/trace_info_subprovider.ts b/packages/sol-cov/src/trace_info_subprovider.ts
new file mode 100644
index 000000000..635a68f58
--- /dev/null
+++ b/packages/sol-cov/src/trace_info_subprovider.ts
@@ -0,0 +1,59 @@
+import * as _ from 'lodash';
+
+import { constants } from './constants';
+import { getTracesByContractAddress } from './trace';
+import { TraceCollectionSubprovider } from './trace_collection_subprovider';
+import { TraceInfo, TraceInfoExistingContract, TraceInfoNewContract } from './types';
+
+// TraceInfoSubprovider is extended by subproviders which need to work with one
+// TraceInfo at a time. It has one abstract method: _handleTraceInfoAsync, which
+// is called for each TraceInfo.
+export abstract class TraceInfoSubprovider extends TraceCollectionSubprovider {
+    protected abstract _handleTraceInfoAsync(traceInfo: TraceInfo): Promise<void>;
+    protected async _recordTxTraceAsync(address: string, data: string | undefined, txHash: string): Promise<void> {
+        await this._web3Wrapper.awaitTransactionMinedAsync(txHash, 0);
+        const trace = await this._web3Wrapper.getTransactionTraceAsync(txHash, {
+            disableMemory: true,
+            disableStack: false,
+            disableStorage: true,
+        });
+        const tracesByContractAddress = getTracesByContractAddress(trace.structLogs, address);
+        const subcallAddresses = _.keys(tracesByContractAddress);
+        if (address === constants.NEW_CONTRACT) {
+            for (const subcallAddress of subcallAddresses) {
+                let traceInfo: TraceInfoNewContract | TraceInfoExistingContract;
+                if (subcallAddress === 'NEW_CONTRACT') {
+                    const traceForThatSubcall = tracesByContractAddress[subcallAddress];
+                    traceInfo = {
+                        subtrace: traceForThatSubcall,
+                        txHash,
+                        address: subcallAddress,
+                        bytecode: data as string,
+                    };
+                } else {
+                    const runtimeBytecode = await this._web3Wrapper.getContractCodeAsync(subcallAddress);
+                    const traceForThatSubcall = tracesByContractAddress[subcallAddress];
+                    traceInfo = {
+                        subtrace: traceForThatSubcall,
+                        txHash,
+                        address: subcallAddress,
+                        runtimeBytecode,
+                    };
+                }
+                await this._handleTraceInfoAsync(traceInfo);
+            }
+        } else {
+            for (const subcallAddress of subcallAddresses) {
+                const runtimeBytecode = await this._web3Wrapper.getContractCodeAsync(subcallAddress);
+                const traceForThatSubcall = tracesByContractAddress[subcallAddress];
+                const traceInfo: TraceInfoExistingContract = {
+                    subtrace: traceForThatSubcall,
+                    txHash,
+                    address: subcallAddress,
+                    runtimeBytecode,
+                };
+                await this._handleTraceInfoAsync(traceInfo);
+            }
+        }
+    }
+}
diff --git a/packages/sol-cov/src/types.ts b/packages/sol-cov/src/types.ts
index 896d4a7b5..cef7141cb 100644
--- a/packages/sol-cov/src/types.ts
+++ b/packages/sol-cov/src/types.ts
@@ -107,3 +107,10 @@ export type TraceInfo = TraceInfoNewContract | TraceInfoExistingContract;
 export enum BlockParamLiteral {
     Latest = 'latest',
 }
+
+export interface EvmCallStackEntry {
+    structLog: StructLog;
+    address: string;
+}
+
+export type EvmCallStack = EvmCallStackEntry[];
diff --git a/packages/sol-cov/src/utils.ts b/packages/sol-cov/src/utils.ts
index 0b32df02e..4f16a1cda 100644
--- a/packages/sol-cov/src/utils.ts
+++ b/packages/sol-cov/src/utils.ts
@@ -1,3 +1,6 @@
+import { addressUtils, BigNumber } from '@0xproject/utils';
+import { OpCode, StructLog } from 'ethereum-types';
+import { addHexPrefix } from 'ethereumjs-util';
 import * as _ from 'lodash';
 
 import { ContractData, LineColumn, SingleFileSourceRange } from './types';
@@ -42,4 +45,25 @@ export const utils = {
         });
         return contractData;
     },
+    isCallLike(op: OpCode): boolean {
+        return _.includes([OpCode.CallCode, OpCode.StaticCall, OpCode.Call, OpCode.DelegateCall], op);
+    },
+    isEndOpcode(op: OpCode): boolean {
+        return _.includes([OpCode.Return, OpCode.Stop, OpCode.Revert, OpCode.Invalid, OpCode.SelfDestruct], op);
+    },
+    getAddressFromStackEntry(stackEntry: string): string {
+        const hexBase = 16;
+        return addressUtils.padZeros(new BigNumber(addHexPrefix(stackEntry)).toString(hexBase));
+    },
+    normalizeStructLogs(structLogs: StructLog[]): StructLog[] {
+        if (structLogs[0].depth === 1) {
+            // Geth uses 1-indexed depth counter whilst ganache starts from 0
+            const newStructLogs = _.map(structLogs, structLog => ({
+                ...structLog,
+                depth: structLog.depth - 1,
+            }));
+            return newStructLogs;
+        }
+        return structLogs;
+    },
 };