add metadata collection for tx-level reverts

Author: dbanks12

barretenberg/cpp/src/barretenberg/vm2/simulation/gadgets/tx_execution.cpp

@@ -143,7 +143,14 @@ TxExecutionResult TxExecution::simulate(const Tx& tx)
     try {
         // Insert revertibles. This can throw if there is a nullifier collision.
         // Such an exception should be handled and the tx be provable.
-        insert_revertibles(tx);
+        // We catch separately here to record the revert reason in call stack metadata,
+        // since no calls have populated the metadata yet at this point.
+        try {
+            insert_revertibles(tx);
+        } catch (const TxExecutionException& e) {
+            call_stack_metadata_collector.notify_tx_revert(e.what());
+            throw;
+        }
 
         // App logic.
         if (tx.app_logic_enqueued_calls.empty()) {

barretenberg/cpp/src/barretenberg/vm2/simulation/interfaces/call_stack_metadata_collector.hpp

@@ -27,6 +27,9 @@ class CallStackMetadataCollectorInterface {
                                   const std::optional<std::string>& halting_message,
                                   const ReturnDataProvider& return_data_provider,
                                   const InternalCallStackProvider& internal_call_stack_provider) = 0;
+    // Notify a tx-level revert that happened outside of an enqueued call (e.g., during revertible insertions).
+    // This creates a synthetic CallStackMetadata entry to capture the revert reason.
+    virtual void notify_tx_revert(const std::string& revert_message) = 0;
     virtual std::vector<CallStackMetadata> dump_call_stack_metadata() = 0;
 };
 

barretenberg/cpp/src/barretenberg/vm2/simulation/lib/call_stack_metadata_collector.cpp

@@ -74,6 +74,29 @@ void CallStackMetadataCollector::notify_exit_call(bool success,
     call_stack_metadata.top().nested.push_back(std::move(top_call_stack_metadata));
 }
 
+void CallStackMetadataCollector::notify_tx_revert(const std::string& revert_message)
+{
+    // Create a synthetic CallStackMetadata entry to capture the revert reason.
+    // This is used when a tx-level revert happens outside of an enqueued call
+    // (e.g., during revertible insertions from private).
+    assert(call_stack_metadata.size() == 1);
+    call_stack_metadata.top().nested.push_back({
+        .timestamp = timestamp++,
+        .phase = current_phase,
+        .contract_address = 0, // No specific contract
+        .caller_pc = 0,
+        .calldata = {},
+        .is_static_call = false,
+        .gas_limit = {},
+        .output = {},
+        .reverted = true,
+        .nested = {},
+        .internal_call_stack_at_exit = {},
+        .halting_message = revert_message,
+        .num_nested_calls = 0,
+    });
+}
+
 std::vector<CallStackMetadata> CallStackMetadataCollector::dump_call_stack_metadata()
 {
     assert(call_stack_metadata.size() == 1);

barretenberg/cpp/src/barretenberg/vm2/simulation/lib/call_stack_metadata_collector.hpp

@@ -26,6 +26,7 @@ class CallStackMetadataCollector : public CallStackMetadataCollectorInterface {
                           const std::optional<std::string>& halting_message,
                           const ReturnDataProvider& return_data_provider,
                           const InternalCallStackProvider& internal_call_stack_provider) override;
+    void notify_tx_revert(const std::string& revert_message) override;
     std::vector<CallStackMetadata> dump_call_stack_metadata() override;
 
   private:
@@ -56,6 +57,7 @@ class NoopCallStackMetadataCollector : public CallStackMetadataCollectorInterfac
                           const ReturnDataProvider&,
                           const InternalCallStackProvider&) override
     {}
+    void notify_tx_revert(const std::string&) override {}
     std::vector<CallStackMetadata> dump_call_stack_metadata() override { return {}; }
 };
 

barretenberg/cpp/src/barretenberg/vm2/simulation/testing/mock_call_stack_metadata_collector.hpp

@@ -29,6 +29,7 @@ class MockCallStackMetadataCollector : public CallStackMetadataCollectorInterfac
                  const ReturnDataProvider& return_data_provider,
                  const InternalCallStackProvider& internal_call_stack_provider),
                 (override));
+    MOCK_METHOD(void, notify_tx_revert, (const std::string& revert_message), (override));
     MOCK_METHOD(std::vector<CallStackMetadata>, dump_call_stack_metadata, (), (override));
 };