Debug OOG txs sent to precompiles

.changeset/big-pumas-fail.md

@@ -0,0 +1,5 @@
+---
+"hardhat": patch
+---
+
+Fixed an edge case where Hardhat would hang if `debug_traceTransaction` was used with an OOG transaction sent to a precompile.

packages/hardhat-core/src/internal/hardhat-network/stack-traces/vm-debug-tracer.ts

@@ -222,7 +222,10 @@ export class VMDebugTracer {
     );
 
     // geth does this for some reason
-    if (result.execResult.exceptionError?.error === "out of gas") {
+    if (
+      rpcStructLogs.length > 0 &&
+      result.execResult.exceptionError?.error === "out of gas"
+    ) {
       rpcStructLogs[rpcStructLogs.length - 1].error = {};
     }
 

packages/hardhat-core/test/internal/hardhat-network/provider/modules/debug.ts

@@ -127,6 +127,31 @@ describe("Debug module", function () {
           assertEqualTraces(trace, modifiesStateTrace);
         });
 
+        it("should trace an OOG transaction sent to a precompile", async function () {
+          await sendDummyTransaction(this.provider, 0, {
+            from: DEFAULT_ACCOUNTS_ADDRESSES[1],
+            to: "0x0000000000000000000000000000000000000001",
+          }).catch(() => {});
+
+          const block = await this.provider.send("eth_getBlockByNumber", [
+            "latest",
+            false,
+          ]);
+
+          const txHash = block.transactions[0];
+
+          const trace: RpcDebugTraceOutput = await this.provider.send(
+            "debug_traceTransaction",
+            [txHash]
+          );
+          assert.deepEqual(trace, {
+            gas: 21_000,
+            failed: true,
+            returnValue: "",
+            structLogs: [],
+          });
+        });
+
         describe("berlin", function () {
           useProvider({ hardfork: "berlin" });