Merge pull request #694 from 0xProject/refactor-sol-cov

Refactor sol-cov to de-duplicate code for coverage and profiling

5 files changed, 264 insertions, 306 deletions

diff --git a/packages/sol-cov/src/coverage_manager.ts b/packages/sol-cov/src/coverage_manager.ts
deleted file mode 100644
index 673a3e600..000000000
--- a/packages/sol-cov/src/coverage_manager.ts
+++ /dev/null
@@ -1,169 +0,0 @@
-import { promisify } from '@0xproject/utils';
-import { stripHexPrefix } from 'ethereumjs-util';
-import * as fs from 'fs';
-import { Collector } from 'istanbul';
-import * as _ from 'lodash';
-import { getLogger, levels, Logger } from 'loglevel';
-import * as mkdirp from 'mkdirp';
-
-import { AbstractArtifactAdapter } from './artifact_adapters/abstract_artifact_adapter';
-import { collectCoverageEntries } from './collect_coverage_entries';
-import { constants } from './constants';
-import { parseSourceMap } from './source_maps';
-import {
-    BranchCoverage,
-    BranchDescription,
-    ContractData,
-    Coverage,
-    FunctionCoverage,
-    FunctionDescription,
-    SingleFileSourceRange,
-    SourceRange,
-    StatementCoverage,
-    StatementDescription,
-    Subtrace,
-    TraceInfo,
-    TraceInfoExistingContract,
-    TraceInfoNewContract,
-} from './types';
-import { utils } from './utils';
-
-const mkdirpAsync = promisify<undefined>(mkdirp);
-
-/**
- * CoverageManager is used by CoverageSubprovider to compute code coverage based on collected trace data.
- */
-export class CoverageManager {
-    private _artifactAdapter: AbstractArtifactAdapter;
-    private _logger: Logger;
-    private _contractsData!: ContractData[];
-    private _collector = new Collector();
-    /**
-     * Computed partial coverage for a single file & subtrace
-     * @param contractData      Contract metadata (source, srcMap, bytecode)
-     * @param subtrace          A subset of a transcation/call trace that was executed within that contract
-     * @param pcToSourceRange   A mapping from program counters to source ranges
-     * @param fileIndex         Index of a file to compute coverage for
-     * @return Partial istanbul coverage for that file & subtrace
-     */
-    private static _getSingleFileCoverageForSubtrace(
-        contractData: ContractData,
-        subtrace: Subtrace,
-        pcToSourceRange: { [programCounter: number]: SourceRange },
-        fileIndex: number,
-    ): Coverage {
-        const absoluteFileName = contractData.sources[fileIndex];
-        const coverageEntriesDescription = collectCoverageEntries(contractData.sourceCodes[fileIndex]);
-        let sourceRanges = _.map(subtrace, structLog => pcToSourceRange[structLog.pc]);
-        sourceRanges = _.compact(sourceRanges); // Some PC's don't map to a source range and we just ignore them.
-        // By default lodash does a shallow object comparasion. We JSON.stringify them and compare as strings.
-        sourceRanges = _.uniqBy(sourceRanges, s => JSON.stringify(s)); // We don't care if one PC was covered multiple times within a single transaction
-        sourceRanges = _.filter(sourceRanges, sourceRange => sourceRange.fileName === absoluteFileName);
-        const branchCoverage: BranchCoverage = {};
-        const branchIds = _.keys(coverageEntriesDescription.branchMap);
-        for (const branchId of branchIds) {
-            const branchDescription = coverageEntriesDescription.branchMap[branchId];
-            const isBranchCoveredByBranchIndex = _.map(branchDescription.locations, location => {
-                const isBranchCovered = _.some(sourceRanges, range => utils.isRangeInside(range.location, location));
-                const timesBranchCovered = Number(isBranchCovered);
-                return timesBranchCovered;
-            });
-            branchCoverage[branchId] = isBranchCoveredByBranchIndex;
-        }
-        const statementCoverage: StatementCoverage = {};
-        const statementIds = _.keys(coverageEntriesDescription.statementMap);
-        for (const statementId of statementIds) {
-            const statementDescription = coverageEntriesDescription.statementMap[statementId];
-            const isStatementCovered = _.some(sourceRanges, range =>
-                utils.isRangeInside(range.location, statementDescription),
-            );
-            const timesStatementCovered = Number(isStatementCovered);
-            statementCoverage[statementId] = timesStatementCovered;
-        }
-        const functionCoverage: FunctionCoverage = {};
-        const functionIds = _.keys(coverageEntriesDescription.fnMap);
-        for (const fnId of functionIds) {
-            const functionDescription = coverageEntriesDescription.fnMap[fnId];
-            const isFunctionCovered = _.some(sourceRanges, range =>
-                utils.isRangeInside(range.location, functionDescription.loc),
-            );
-            const timesFunctionCovered = Number(isFunctionCovered);
-            functionCoverage[fnId] = timesFunctionCovered;
-        }
-        // HACK: Solidity doesn't emit any opcodes that map back to modifiers with no args, that's why we map back to the
-        // function range and check if there is any covered statement within that range.
-        for (const modifierStatementId of coverageEntriesDescription.modifiersStatementIds) {
-            if (statementCoverage[modifierStatementId]) {
-                // Already detected as covered
-                continue;
-            }
-            const modifierDescription = coverageEntriesDescription.statementMap[modifierStatementId];
-            const enclosingFunction = _.find(coverageEntriesDescription.fnMap, functionDescription =>
-                utils.isRangeInside(modifierDescription, functionDescription.loc),
-            ) as FunctionDescription;
-            const isModifierCovered = _.some(
-                coverageEntriesDescription.statementMap,
-                (statementDescription: StatementDescription, statementId: number) => {
-                    const isInsideTheModifierEnclosingFunction = utils.isRangeInside(
-                        statementDescription,
-                        enclosingFunction.loc,
-                    );
-                    const isCovered = statementCoverage[statementId];
-                    return isInsideTheModifierEnclosingFunction && isCovered;
-                },
-            );
-            const timesModifierCovered = Number(isModifierCovered);
-            statementCoverage[modifierStatementId] = timesModifierCovered;
-        }
-        const partialCoverage = {
-            [absoluteFileName]: {
-                ...coverageEntriesDescription,
-                path: absoluteFileName,
-                f: functionCoverage,
-                s: statementCoverage,
-                b: branchCoverage,
-            },
-        };
-        return partialCoverage;
-    }
-    constructor(artifactAdapter: AbstractArtifactAdapter, isVerbose: boolean) {
-        this._artifactAdapter = artifactAdapter;
-        this._logger = getLogger('sol-cov');
-        this._logger.setLevel(isVerbose ? levels.TRACE : levels.ERROR);
-    }
-    public async writeCoverageAsync(): Promise<void> {
-        const finalCoverage = this._collector.getFinalCoverage();
-        const stringifiedCoverage = JSON.stringify(finalCoverage, null, '\t');
-        await mkdirpAsync('coverage');
-        fs.writeFileSync('coverage/coverage.json', stringifiedCoverage);
-    }
-    public async computeSingleTraceCoverageAsync(traceInfo: TraceInfo): Promise<void> {
-        if (_.isUndefined(this._contractsData)) {
-            this._contractsData = await this._artifactAdapter.collectContractsDataAsync();
-        }
-        const isContractCreation = traceInfo.address === constants.NEW_CONTRACT;
-        const bytecode = isContractCreation
-            ? (traceInfo as TraceInfoNewContract).bytecode
-            : (traceInfo as TraceInfoExistingContract).runtimeBytecode;
-        const contractData = utils.getContractDataIfExists(this._contractsData, bytecode);
-        if (_.isUndefined(contractData)) {
-            const errMsg = isContractCreation
-                ? `Unknown contract creation transaction`
-                : `Transaction to an unknown address: ${traceInfo.address}`;
-            this._logger.warn(errMsg);
-            return;
-        }
-        const bytecodeHex = stripHexPrefix(bytecode);
-        const sourceMap = isContractCreation ? contractData.sourceMap : contractData.sourceMapRuntime;
-        const pcToSourceRange = parseSourceMap(contractData.sourceCodes, sourceMap, bytecodeHex, contractData.sources);
-        for (let fileIndex = 0; fileIndex < contractData.sources.length; fileIndex++) {
-            const singleFileCoverageForTrace = CoverageManager._getSingleFileCoverageForSubtrace(
-                contractData,
-                traceInfo.subtrace,
-                pcToSourceRange,
-                fileIndex,
-            );
-            this._collector.add(singleFileCoverageForTrace);
-        }
-    }
-}
diff --git a/packages/sol-cov/src/coverage_subprovider.ts b/packages/sol-cov/src/coverage_subprovider.ts
index 3529fb885..0fa7f873e 100644
--- a/packages/sol-cov/src/coverage_subprovider.ts
+++ b/packages/sol-cov/src/coverage_subprovider.ts
@@ -1,14 +1,29 @@
+import * as _ from 'lodash';
+
 import { AbstractArtifactAdapter } from './artifact_adapters/abstract_artifact_adapter';
-import { CoverageManager } from './coverage_manager';
+import { collectCoverageEntries } from './collect_coverage_entries';
 import { TraceCollectionSubprovider } from './trace_collection_subprovider';
-import { TraceInfo } from './types';
+import { SingleFileSubtraceHandler, TraceCollector } from './trace_collector';
+import {
+    BranchCoverage,
+    ContractData,
+    Coverage,
+    FunctionCoverage,
+    FunctionDescription,
+    SourceRange,
+    StatementCoverage,
+    StatementDescription,
+    Subtrace,
+    TraceInfo,
+} from './types';
+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 {
-    private _coverageManager: CoverageManager;
+    private _coverageCollector: TraceCollector;
     /**
      * Instantiates a CoverageSubprovider instance
      * @param artifactAdapter Adapter for used artifacts format (0x, truffle, giveth, etc.)
@@ -22,15 +37,104 @@ export class CoverageSubprovider extends TraceCollectionSubprovider {
             shouldCollectCallTraces: true,
         };
         super(defaultFromAddress, traceCollectionSubproviderConfig);
-        this._coverageManager = new CoverageManager(artifactAdapter, isVerbose);
+        this._coverageCollector = new TraceCollector(artifactAdapter, isVerbose, coverageHandler);
     }
     public async handleTraceInfoAsync(traceInfo: TraceInfo): Promise<void> {
-        await this._coverageManager.computeSingleTraceCoverageAsync(traceInfo);
+        await this._coverageCollector.computeSingleTraceCoverageAsync(traceInfo);
     }
     /**
      * Write the test coverage results to a file in Istanbul format.
      */
     public async writeCoverageAsync(): Promise<void> {
-        await this._coverageManager.writeCoverageAsync();
+        await this._coverageCollector.writeOutputAsync();
     }
 }
+
+/**
+ * Computed partial coverage for a single file & subtrace.
+ * @param contractData      Contract metadata (source, srcMap, bytecode)
+ * @param subtrace          A subset of a transcation/call trace that was executed within that contract
+ * @param pcToSourceRange   A mapping from program counters to source ranges
+ * @param fileIndex         Index of a file to compute coverage for
+ * @return Partial istanbul coverage for that file & subtrace
+ */
+export const coverageHandler: SingleFileSubtraceHandler = (
+    contractData: ContractData,
+    subtrace: Subtrace,
+    pcToSourceRange: { [programCounter: number]: SourceRange },
+    fileIndex: number,
+): Coverage => {
+    const absoluteFileName = contractData.sources[fileIndex];
+    const coverageEntriesDescription = collectCoverageEntries(contractData.sourceCodes[fileIndex]);
+    let sourceRanges = _.map(subtrace, structLog => pcToSourceRange[structLog.pc]);
+    sourceRanges = _.compact(sourceRanges); // Some PC's don't map to a source range and we just ignore them.
+    // By default lodash does a shallow object comparasion. We JSON.stringify them and compare as strings.
+    sourceRanges = _.uniqBy(sourceRanges, s => JSON.stringify(s)); // We don't care if one PC was covered multiple times within a single transaction
+    sourceRanges = _.filter(sourceRanges, sourceRange => sourceRange.fileName === absoluteFileName);
+    const branchCoverage: BranchCoverage = {};
+    const branchIds = _.keys(coverageEntriesDescription.branchMap);
+    for (const branchId of branchIds) {
+        const branchDescription = coverageEntriesDescription.branchMap[branchId];
+        const isBranchCoveredByBranchIndex = _.map(branchDescription.locations, location => {
+            const isBranchCovered = _.some(sourceRanges, range => utils.isRangeInside(range.location, location));
+            const timesBranchCovered = Number(isBranchCovered);
+            return timesBranchCovered;
+        });
+        branchCoverage[branchId] = isBranchCoveredByBranchIndex;
+    }
+    const statementCoverage: StatementCoverage = {};
+    const statementIds = _.keys(coverageEntriesDescription.statementMap);
+    for (const statementId of statementIds) {
+        const statementDescription = coverageEntriesDescription.statementMap[statementId];
+        const isStatementCovered = _.some(sourceRanges, range =>
+            utils.isRangeInside(range.location, statementDescription),
+        );
+        const timesStatementCovered = Number(isStatementCovered);
+        statementCoverage[statementId] = timesStatementCovered;
+    }
+    const functionCoverage: FunctionCoverage = {};
+    const functionIds = _.keys(coverageEntriesDescription.fnMap);
+    for (const fnId of functionIds) {
+        const functionDescription = coverageEntriesDescription.fnMap[fnId];
+        const isFunctionCovered = _.some(sourceRanges, range =>
+            utils.isRangeInside(range.location, functionDescription.loc),
+        );
+        const timesFunctionCovered = Number(isFunctionCovered);
+        functionCoverage[fnId] = timesFunctionCovered;
+    }
+    // HACK: Solidity doesn't emit any opcodes that map back to modifiers with no args, that's why we map back to the
+    // function range and check if there is any covered statement within that range.
+    for (const modifierStatementId of coverageEntriesDescription.modifiersStatementIds) {
+        if (statementCoverage[modifierStatementId]) {
+            // Already detected as covered
+            continue;
+        }
+        const modifierDescription = coverageEntriesDescription.statementMap[modifierStatementId];
+        const enclosingFunction = _.find(coverageEntriesDescription.fnMap, functionDescription =>
+            utils.isRangeInside(modifierDescription, functionDescription.loc),
+        ) as FunctionDescription;
+        const isModifierCovered = _.some(
+            coverageEntriesDescription.statementMap,
+            (statementDescription: StatementDescription, statementId: number) => {
+                const isInsideTheModifierEnclosingFunction = utils.isRangeInside(
+                    statementDescription,
+                    enclosingFunction.loc,
+                );
+                const isCovered = statementCoverage[statementId];
+                return isInsideTheModifierEnclosingFunction && isCovered;
+            },
+        );
+        const timesModifierCovered = Number(isModifierCovered);
+        statementCoverage[modifierStatementId] = timesModifierCovered;
+    }
+    const partialCoverage = {
+        [absoluteFileName]: {
+            ...coverageEntriesDescription,
+            path: absoluteFileName,
+            f: functionCoverage,
+            s: statementCoverage,
+            b: branchCoverage,
+        },
+    };
+    return partialCoverage;
+};
diff --git a/packages/sol-cov/src/profiler_manager.ts b/packages/sol-cov/src/profiler_manager.ts
deleted file mode 100644
index 88e183cbd..000000000
--- a/packages/sol-cov/src/profiler_manager.ts
+++ /dev/null
@@ -1,125 +0,0 @@
-import { promisify } from '@0xproject/utils';
-import { stripHexPrefix } from 'ethereumjs-util';
-import * as fs from 'fs';
-import { Collector } from 'istanbul';
-import * as _ from 'lodash';
-import { getLogger, levels, Logger } from 'loglevel';
-import * as mkdirp from 'mkdirp';
-
-import { AbstractArtifactAdapter } from './artifact_adapters/abstract_artifact_adapter';
-import { collectCoverageEntries } from './collect_coverage_entries';
-import { constants } from './constants';
-import { parseSourceMap } from './source_maps';
-import {
-    ContractData,
-    Coverage,
-    SingleFileSourceRange,
-    SourceRange,
-    Subtrace,
-    TraceInfo,
-    TraceInfoExistingContract,
-    TraceInfoNewContract,
-} from './types';
-import { utils } from './utils';
-
-const mkdirpAsync = promisify<undefined>(mkdirp);
-
-/**
- * ProfilerManager is used by ProfilerSubprovider to profile code while running Solidity tests based on collected trace data.
- * HACK: It's almost the exact copy of CoverageManager but instead of reporting how much times was each statement executed - it reports - how expensive it was gaswise.
- */
-export class ProfilerManager {
-    private _artifactAdapter: AbstractArtifactAdapter;
-    private _logger: Logger;
-    private _contractsData!: ContractData[];
-    private _collector = new Collector();
-    /**
-     * Computed partial coverage for a single file & subtrace
-     * @param contractData      Contract metadata (source, srcMap, bytecode)
-     * @param subtrace          A subset of a transcation/call trace that was executed within that contract
-     * @param pcToSourceRange   A mapping from program counters to source ranges
-     * @param fileIndex         Index of a file to compute coverage for
-     * @return Partial istanbul coverage for that file & subtrace
-     */
-    private static _getSingleFileCoverageForSubtrace(
-        contractData: ContractData,
-        subtrace: Subtrace,
-        pcToSourceRange: { [programCounter: number]: SourceRange },
-        fileIndex: number,
-    ): Coverage {
-        const absoluteFileName = contractData.sources[fileIndex];
-        const profilerEntriesDescription = collectCoverageEntries(contractData.sourceCodes[fileIndex]);
-        const gasConsumedByStatement: { [statementId: string]: number } = {};
-        const statementIds = _.keys(profilerEntriesDescription.statementMap);
-        for (const statementId of statementIds) {
-            const statementDescription = profilerEntriesDescription.statementMap[statementId];
-            const totalGasCost = _.sum(
-                _.map(subtrace, structLog => {
-                    const sourceRange = pcToSourceRange[structLog.pc];
-                    if (_.isUndefined(sourceRange)) {
-                        return 0;
-                    }
-                    if (sourceRange.fileName !== absoluteFileName) {
-                        return 0;
-                    }
-                    if (utils.isRangeInside(sourceRange.location, statementDescription)) {
-                        return structLog.gasCost;
-                    } else {
-                        return 0;
-                    }
-                }),
-            );
-            gasConsumedByStatement[statementId] = totalGasCost;
-        }
-        const partialProfilerOutput = {
-            [absoluteFileName]: {
-                ...profilerEntriesDescription,
-                path: absoluteFileName,
-                f: {}, // I's meaningless in profiling context
-                s: gasConsumedByStatement,
-                b: {}, // I's meaningless in profiling context
-            },
-        };
-        return partialProfilerOutput;
-    }
-    constructor(artifactAdapter: AbstractArtifactAdapter, isVerbose: boolean) {
-        this._artifactAdapter = artifactAdapter;
-        this._logger = getLogger('sol-cov');
-        this._logger.setLevel(isVerbose ? levels.TRACE : levels.ERROR);
-    }
-    public async writeProfilerOutputAsync(): Promise<void> {
-        const finalCoverage = this._collector.getFinalCoverage();
-        const stringifiedCoverage = JSON.stringify(finalCoverage, null, '\t');
-        await mkdirpAsync('coverage');
-        fs.writeFileSync('coverage/coverage.json', stringifiedCoverage);
-    }
-    public async computeSingleTraceCoverageAsync(traceInfo: TraceInfo): Promise<void> {
-        if (_.isUndefined(this._contractsData)) {
-            this._contractsData = await this._artifactAdapter.collectContractsDataAsync();
-        }
-        const isContractCreation = traceInfo.address === constants.NEW_CONTRACT;
-        const bytecode = isContractCreation
-            ? (traceInfo as TraceInfoNewContract).bytecode
-            : (traceInfo as TraceInfoExistingContract).runtimeBytecode;
-        const contractData = utils.getContractDataIfExists(this._contractsData, bytecode);
-        if (_.isUndefined(contractData)) {
-            const errMsg = isContractCreation
-                ? `Unknown contract creation transaction`
-                : `Transaction to an unknown address: ${traceInfo.address}`;
-            this._logger.warn(errMsg);
-            return;
-        }
-        const bytecodeHex = stripHexPrefix(bytecode);
-        const sourceMap = isContractCreation ? contractData.sourceMap : contractData.sourceMapRuntime;
-        const pcToSourceRange = parseSourceMap(contractData.sourceCodes, sourceMap, bytecodeHex, contractData.sources);
-        for (let fileIndex = 0; fileIndex < contractData.sources.length; fileIndex++) {
-            const singleFileCoverageForTrace = ProfilerManager._getSingleFileCoverageForSubtrace(
-                contractData,
-                traceInfo.subtrace,
-                pcToSourceRange,
-                fileIndex,
-            );
-            this._collector.add(singleFileCoverageForTrace);
-        }
-    }
-}
diff --git a/packages/sol-cov/src/profiler_subprovider.ts b/packages/sol-cov/src/profiler_subprovider.ts
index 9fd815f07..62ed1b472 100644
--- a/packages/sol-cov/src/profiler_subprovider.ts
+++ b/packages/sol-cov/src/profiler_subprovider.ts
@@ -1,14 +1,18 @@
+import * as _ from 'lodash';
+
 import { AbstractArtifactAdapter } from './artifact_adapters/abstract_artifact_adapter';
-import { ProfilerManager } from './profiler_manager';
+import { collectCoverageEntries } from './collect_coverage_entries';
 import { TraceCollectionSubprovider } from './trace_collection_subprovider';
-import { TraceInfo } from './types';
+import { SingleFileSubtraceHandler, TraceCollector } from './trace_collector';
+import { ContractData, Coverage, SourceRange, Subtrace, TraceInfo } from './types';
+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 {
-    private _profilerManager: ProfilerManager;
+    private _profilerCollector: TraceCollector;
     /**
      * Instantiates a ProfilerSubprovider instance
      * @param artifactAdapter Adapter for used artifacts format (0x, truffle, giveth, etc.)
@@ -22,15 +26,66 @@ export class ProfilerSubprovider extends TraceCollectionSubprovider {
             shouldCollectCallTraces: false,
         };
         super(defaultFromAddress, traceCollectionSubproviderConfig);
-        this._profilerManager = new ProfilerManager(artifactAdapter, isVerbose);
+        this._profilerCollector = new TraceCollector(artifactAdapter, isVerbose, profilerHandler);
     }
     public async handleTraceInfoAsync(traceInfo: TraceInfo): Promise<void> {
-        await this._profilerManager.computeSingleTraceCoverageAsync(traceInfo);
+        await this._profilerCollector.computeSingleTraceCoverageAsync(traceInfo);
     }
     /**
      * Write the test profiler results to a file in Istanbul format.
      */
     public async writeProfilerOutputAsync(): Promise<void> {
-        await this._profilerManager.writeProfilerOutputAsync();
+        await this._profilerCollector.writeOutputAsync();
     }
 }
+
+/**
+ * Computed partial coverage for a single file & subtrace for the purposes of
+ * gas profiling.
+ * @param contractData      Contract metadata (source, srcMap, bytecode)
+ * @param subtrace          A subset of a transcation/call trace that was executed within that contract
+ * @param pcToSourceRange   A mapping from program counters to source ranges
+ * @param fileIndex         Index of a file to compute coverage for
+ * @return Partial istanbul coverage for that file & subtrace
+ */
+export const profilerHandler: SingleFileSubtraceHandler = (
+    contractData: ContractData,
+    subtrace: Subtrace,
+    pcToSourceRange: { [programCounter: number]: SourceRange },
+    fileIndex: number,
+): Coverage => {
+    const absoluteFileName = contractData.sources[fileIndex];
+    const profilerEntriesDescription = collectCoverageEntries(contractData.sourceCodes[fileIndex]);
+    const gasConsumedByStatement: { [statementId: string]: number } = {};
+    const statementIds = _.keys(profilerEntriesDescription.statementMap);
+    for (const statementId of statementIds) {
+        const statementDescription = profilerEntriesDescription.statementMap[statementId];
+        const totalGasCost = _.sum(
+            _.map(subtrace, structLog => {
+                const sourceRange = pcToSourceRange[structLog.pc];
+                if (_.isUndefined(sourceRange)) {
+                    return 0;
+                }
+                if (sourceRange.fileName !== absoluteFileName) {
+                    return 0;
+                }
+                if (utils.isRangeInside(sourceRange.location, statementDescription)) {
+                    return structLog.gasCost;
+                } else {
+                    return 0;
+                }
+            }),
+        );
+        gasConsumedByStatement[statementId] = totalGasCost;
+    }
+    const partialProfilerOutput = {
+        [absoluteFileName]: {
+            ...profilerEntriesDescription,
+            path: absoluteFileName,
+            f: {}, // I's meaningless in profiling context
+            s: gasConsumedByStatement,
+            b: {}, // I's meaningless in profiling context
+        },
+    };
+    return partialProfilerOutput;
+};
diff --git a/packages/sol-cov/src/trace_collector.ts b/packages/sol-cov/src/trace_collector.ts
new file mode 100644
index 000000000..1b458edec
--- /dev/null
+++ b/packages/sol-cov/src/trace_collector.ts
@@ -0,0 +1,93 @@
+import { promisify } from '@0xproject/utils';
+import { stripHexPrefix } from 'ethereumjs-util';
+import * as fs from 'fs';
+import { Collector } from 'istanbul';
+import * as _ from 'lodash';
+import { getLogger, levels, Logger } from 'loglevel';
+import * as mkdirp from 'mkdirp';
+
+import { AbstractArtifactAdapter } from './artifact_adapters/abstract_artifact_adapter';
+import { constants } from './constants';
+import { parseSourceMap } from './source_maps';
+import {
+    ContractData,
+    Coverage,
+    SourceRange,
+    Subtrace,
+    TraceInfo,
+    TraceInfoExistingContract,
+    TraceInfoNewContract,
+} from './types';
+import { utils } from './utils';
+
+const mkdirpAsync = promisify<undefined>(mkdirp);
+
+export type SingleFileSubtraceHandler = (
+    contractData: ContractData,
+    subtrace: Subtrace,
+    pcToSourceRange: { [programCounter: number]: SourceRange },
+    fileIndex: number,
+) => Coverage;
+
+/**
+ * TraceCollector is used by CoverageSubprovider to compute code coverage based on collected trace data.
+ */
+export class TraceCollector {
+    private _artifactAdapter: AbstractArtifactAdapter;
+    private _logger: Logger;
+    private _contractsData!: ContractData[];
+    private _collector = new Collector();
+    private _singleFileSubtraceHandler: SingleFileSubtraceHandler;
+
+    /**
+     * Instantiates a TraceCollector instance
+     * @param artifactAdapter Adapter for used artifacts format (0x, truffle, giveth, etc.)
+     * @param isVerbose If true, we will log any unknown transactions. Otherwise we will ignore them
+     * @param singleFileSubtraceHandler A handler function for computing partial coverage for a single file & subtrace
+     */
+    constructor(
+        artifactAdapter: AbstractArtifactAdapter,
+        isVerbose: boolean,
+        singleFileSubtraceHandler: SingleFileSubtraceHandler,
+    ) {
+        this._artifactAdapter = artifactAdapter;
+        this._logger = getLogger('sol-cov');
+        this._logger.setLevel(isVerbose ? levels.TRACE : levels.ERROR);
+        this._singleFileSubtraceHandler = singleFileSubtraceHandler;
+    }
+    public async writeOutputAsync(): Promise<void> {
+        const finalCoverage = this._collector.getFinalCoverage();
+        const stringifiedCoverage = JSON.stringify(finalCoverage, null, '\t');
+        await mkdirpAsync('coverage');
+        fs.writeFileSync('coverage/coverage.json', stringifiedCoverage);
+    }
+    public async computeSingleTraceCoverageAsync(traceInfo: TraceInfo): Promise<void> {
+        if (_.isUndefined(this._contractsData)) {
+            this._contractsData = await this._artifactAdapter.collectContractsDataAsync();
+        }
+        const isContractCreation = traceInfo.address === constants.NEW_CONTRACT;
+        const bytecode = isContractCreation
+            ? (traceInfo as TraceInfoNewContract).bytecode
+            : (traceInfo as TraceInfoExistingContract).runtimeBytecode;
+        const contractData = utils.getContractDataIfExists(this._contractsData, bytecode);
+        if (_.isUndefined(contractData)) {
+            const errMsg = isContractCreation
+                ? `Unknown contract creation transaction`
+                : `Transaction to an unknown address: ${traceInfo.address}`;
+            this._logger.warn(errMsg);
+            return;
+        }
+        const bytecodeHex = stripHexPrefix(bytecode);
+        const sourceMap = isContractCreation ? contractData.sourceMap : contractData.sourceMapRuntime;
+        const pcToSourceRange = parseSourceMap(contractData.sourceCodes, sourceMap, bytecodeHex, contractData.sources);
+        for (let fileIndex = 0; fileIndex < contractData.sources.length; fileIndex++) {
+            const singleFileCoverageForTrace = this._singleFileSubtraceHandler(
+                contractData,
+                traceInfo.subtrace,
+                pcToSourceRange,
+                fileIndex,
+            );
+            this._collector.add(singleFileCoverageForTrace);
+        }
+    }
+}