From 06367ba3ab267cd9f899c374b423dff2a34f0a16 Mon Sep 17 00:00:00 2001
From: Runtian Zhou <runtian@aptoslabs.com>
Date: Thu, 26 Oct 2023 11:27:12 -0700
Subject: [PATCH] [api] Add contextual information to VMStatus::Error

---
 api/src/tests/transactions_test.rs            | 26 +++++++++++++++++++
 api/src/transactions.rs                       | 20 ++++++++++++--
 .../move-vm/types/src/values/values_impl.rs   |  5 +++-
 3 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/api/src/tests/transactions_test.rs b/api/src/tests/transactions_test.rs
index 7a4c1cf9a201e..d472110446757 100644
--- a/api/src/tests/transactions_test.rs
+++ b/api/src/tests/transactions_test.rs
@@ -1372,6 +1372,32 @@ async fn test_gas_estimation_static_override() {
     context.check_golden_output(resp);
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn simulation_failure_error_message() {
+    let mut context = new_test_context(current_function_name!());
+    let admin0 = context.root_account().await;
+
+    // script {
+    //     fun main() {
+    //         1/0;
+    //     }
+    // }
+
+    let output = context.simulate_transaction(&admin0, json!({
+        "type": "script_payload",
+        "code": {
+            "bytecode": "a11ceb0b030000000105000100000000050601000000000000000600000000000000001a0102",
+        },
+        "type_arguments": [],
+        "arguments": [],
+    }), 200).await;
+
+    assert!(output.as_array().unwrap()[0]["vm_status"]
+        .as_str()
+        .unwrap()
+        .contains("Division by zero"));
+}
+
 fn gen_string(len: u64) -> String {
     let mut rng = thread_rng();
     std::iter::repeat(())
diff --git a/api/src/transactions.rs b/api/src/transactions.rs
index 7039fb3476e2b..6829d82b0785e 100644
--- a/api/src/transactions.rs
+++ b/api/src/transactions.rs
@@ -39,6 +39,7 @@ use aptos_types::{
     vm_status::StatusCode,
 };
 use aptos_vm::{data_cache::AsMoveResolver, AptosVM};
+use move_core_types::vm_status::VMStatus;
 use poem_openapi::{
     param::{Path, Query},
     payload::Json,
@@ -1188,7 +1189,7 @@ impl TransactionsApi {
         // Simulate transaction
         let state_view = self.context.latest_state_view_poem(&ledger_info)?;
         let move_resolver = state_view.as_move_resolver();
-        let (_, output) = AptosVM::simulate_signed_transaction(&txn, &move_resolver);
+        let (vm_status, output) = AptosVM::simulate_signed_transaction(&txn, &move_resolver);
         let version = ledger_info.version();
 
         // Ensure that all known statuses return their values in the output (even if they aren't supposed to)
@@ -1230,7 +1231,22 @@ impl TransactionsApi {
                 let mut user_transactions = Vec::new();
                 for transaction in transactions.into_iter() {
                     match transaction {
-                        Transaction::UserTransaction(user_txn) => user_transactions.push(*user_txn),
+                        Transaction::UserTransaction(user_txn) => {
+                            let mut txn = *user_txn;
+                            match &vm_status {
+                                VMStatus::Error {
+                                    message: Some(msg), ..
+                                }
+                                | VMStatus::ExecutionFailure {
+                                    message: Some(msg), ..
+                                } => {
+                                    txn.info.vm_status +=
+                                        format!("\nExecution failed with status: {}", msg).as_str();
+                                },
+                                _ => (),
+                            }
+                            user_transactions.push(txn);
+                        },
                         _ => {
                             return Err(SubmitTransactionError::internal_with_code(
                                 "Simulation transaction resulted in a non-UserTransaction",
diff --git a/third_party/move/move-vm/types/src/values/values_impl.rs b/third_party/move/move-vm/types/src/values/values_impl.rs
index 3c94feafdfbf6..cec718f44b029 100644
--- a/third_party/move/move-vm/types/src/values/values_impl.rs
+++ b/third_party/move/move-vm/types/src/values/values_impl.rs
@@ -1517,7 +1517,10 @@ impl IntegerValue {
                 return Err(PartialVMError::new(StatusCode::INTERNAL_TYPE_ERROR).with_message(msg));
             },
         };
-        res.ok_or_else(|| PartialVMError::new(StatusCode::ARITHMETIC_ERROR))
+        res.ok_or_else(|| {
+            PartialVMError::new(StatusCode::ARITHMETIC_ERROR)
+                .with_message("Division by zero error".to_string())
+        })
     }
 
     pub fn rem_checked(self, other: Self) -> PartialVMResult<Self> {