1 files changed, 104 insertions, 0 deletions
diff --git a/packages/sol-cov/src/trace.ts b/packages/sol-cov/src/trace.ts
new file mode 100644
index 000000000..cb5410909
--- /dev/null
+++ b/packages/sol-cov/src/trace.ts
@@ -0,0 +1,104 @@
+import { OpCode, StructLog, TransactionTrace } from '@0xproject/types';
+import { addressUtils, BigNumber, logUtils } from '@0xproject/utils';
+import { addHexPrefix, stripHexPrefix } from 'ethereumjs-util';
+import * as fs from 'fs';
+import * as _ from 'lodash';
+
+export interface TraceByContractAddress {
+    [contractAddress: string]: StructLog[];
+}
+
+function getAddressFromStackEntry(stackEntry: string): string {
+    return addressUtils.padZeros(new BigNumber(addHexPrefix(stackEntry)).toString(16));
+}
+
+export function getTracesByContractAddress(structLogs: StructLog[], startAddress: string): TraceByContractAddress {
+    const traceByContractAddress: TraceByContractAddress = {};
+    let currentTraceSegment = [];
+    const callStack = [startAddress];
+    // 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) {
+            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
+        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;
+            const jumpAddressOffset = 1;
+            const newAddress = 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];
+            if (nextStructLog.depth !== structLog.depth) {
+                callStack.push(newAddress);
+                traceByContractAddress[currentAddress] = (traceByContractAddress[currentAddress] || []).concat(
+                    currentTraceSegment,
+                );
+                currentTraceSegment = [];
+            }
+        } else if (isEndOpcode) {
+            const currentAddress = callStack.pop() as string;
+            traceByContractAddress[currentAddress] = (traceByContractAddress[currentAddress] || []).concat(
+                currentTraceSegment,
+            );
+            currentTraceSegment = [];
+            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.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 traceByContractAddress;
+        } else {
+            if (structLog !== _.last(structLogs)) {
+                const nextStructLog = structLogs[i + 1];
+                if (nextStructLog.depth === structLog.depth) {
+                    continue;
+                } else if (nextStructLog.depth === structLog.depth - 1) {
+                    const currentAddress = callStack.pop() as string;
+                    traceByContractAddress[currentAddress] = (traceByContractAddress[currentAddress] || []).concat(
+                        currentTraceSegment,
+                    );
+                    currentTraceSegment = [];
+                } else {
+                    throw new Error('Malformed trace. Unexpected call depth change');
+                }
+            }
+        }
+    }
+    if (callStack.length !== 0) {
+        throw new Error('Malformed trace. Call stack non empty at the end');
+    }
+    if (currentTraceSegment.length !== 0) {
+        throw new Error('Malformed trace. Current trace segment non empty at the end');
+    }
+    return traceByContractAddress;
+}