feat(rpc): greatly enhance simulate RPC

API-CHANGELOG.md

@@ -71,6 +71,12 @@ This release contains bug fixes only and no API changes.
 
 This release contains bug fixes only and no API changes.
 
+## Unreleased
+
+### Additions and bugfixes
+
+- `simulate`: There is now additional support for simulating transactions in past ledgers, by providing the `ledger_index` or `ledger_hash`.
+
 ## XRP Ledger server version 2.5.0
 
 [Version 2.5.0](https://github.com/XRPLF/rippled/releases/tag/2.5.0) was released on Jun 24, 2025.

include/xrpl/protocol/jss.h

@@ -627,7 +627,7 @@ JSS(trusted_validator_keys);  // out: ValidatorList
 JSS(tx);                      // out: STTx, AccountTx*
 JSS(tx_blob);                 // in/out: Submit,
                               // in: TransactionSign, AccountTx*
-JSS(tx_hash);                 // in: TransactionEntry
+JSS(tx_hash);                 // in: TransactionEntry, simulate
 JSS(tx_json);                 // in/out: TransactionSign
                               // out: TransactionEntry
 JSS(tx_signing_hash);         // out: TransactionSign

include/xrpl/tx/apply.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <xrpl/beast/utility/Journal.h>
+#include <xrpl/core/ServiceRegistry.h>
 #include <xrpl/ledger/View.h>
 #include <xrpl/protocol/STTx.h>
 #include <xrpl/tx/applySteps.h>
@@ -115,6 +116,14 @@ enum class ApplyTransactionResult {
     Retry
 };
 
+std::optional<std::vector<ApplyResult>>
+applyBatchTransactions(
+    ServiceRegistry& registry,
+    OpenView& batchView,
+    STTx const& batchTxn,
+    ApplyFlags flags,
+    beast::Journal j);
+
 /** Transaction application helper
 
     Provides more detailed logging and decodes the

src/libxrpl/ledger/ApplyStateTable.cpp

@@ -246,11 +246,8 @@ ApplyStateTable::apply(
         metadata = meta;
     }
 
-    if (!isDryRun)
-    {
-        to.rawTxInsert(tx.getTransactionID(), sTx, sMeta);
-        apply(to);
-    }
+    to.rawTxInsert(tx.getTransactionID(), sTx, sMeta);
+    apply(to);
     return metadata;
 }
 

src/libxrpl/tx/apply.cpp

@@ -135,11 +135,12 @@
     });
 }
 
-static bool
+std::optional<std::vector<ApplyResult>>
 applyBatchTransactions(
     ServiceRegistry& registry,
     OpenView& batchView,
     STTx const& batchTxn,
+    ApplyFlags flags,
     beast::Journal j)
 {
     XRPL_ASSERT(
@@ -149,41 +150,57 @@
     auto const parentBatchId = batchTxn.getTransactionID();
     auto const mode = batchTxn.getFlags();
 
-    auto applyOneTransaction = [&registry, &j, &parentBatchId, &batchView](STTx&& tx) {
+    auto applyOneTransaction = [&registry, &j, &parentBatchId, &batchView, &flags](STTx&& tx) {
         OpenView perTxBatchView(batch_view, batchView);
 
-        auto const ret = apply(registry, perTxBatchView, parentBatchId, tx, tapBATCH, j);
-        XRPL_ASSERT(
-            ret.applied == (isTesSuccess(ret.ter) || isTecClaim(ret.ter)),
-            "Inner transaction should not be applied");
+        auto const ret =
+            apply(registry, perTxBatchView, parentBatchId, tx, (flags & tapDRY_RUN) | tapBATCH, j);
+        if (flags & tapDRY_RUN)
+        {
+            XRPL_ASSERT(ret.applied == false, "Inner transaction should not be applied in dry run");
+        }
+        else
+        {
+            XRPL_ASSERT(
+                ret.applied == (isTesSuccess(ret.ter) || isTecClaim(ret.ter)),
+                "Inner transaction should not be applied");
+        }
 
         JLOG(j.debug()) << "BatchTrace[" << parentBatchId << "]: " << tx.getTransactionID() << " "
                         << (ret.applied ? "applied" : "failure") << ": " << transToken(ret.ter);
 
         // If the transaction should be applied push its changes to the
         // whole-batch view.
-        if (ret.applied && (isTesSuccess(ret.ter) || isTecClaim(ret.ter)))
+        if ((ret.applied || flags & tapDRY_RUN) && (isTesSuccess(ret.ter) || isTecClaim(ret.ter)))
             perTxBatchView.apply(batchView);
 
         return ret;
     };
 
-    int applied = 0;
+    std::vector<ApplyResult> results;
 
     for (STObject rb : batchTxn.getFieldArray(sfRawTransactions))
     {
         auto const result = applyOneTransaction(STTx{std::move(rb)});
-        XRPL_ASSERT(
-            result.applied == (isTesSuccess(result.ter) || isTecClaim(result.ter)),
-            "Outer Batch failure, inner transaction should not be applied");
+        if (flags & tapDRY_RUN)
+        {
+            XRPL_ASSERT(
+                result.applied == false, "Inner transaction should not be applied in dry run");
+        }
+        else
+        {
+            XRPL_ASSERT(
+                result.applied == (isTesSuccess(result.ter) || isTecClaim(result.ter)),
+                "Outer Batch failure, inner transaction should not be applied");
+        }
 
-        if (result.applied)
-            ++applied;
+        if (result.applied || flags & tapDRY_RUN)
+            results.push_back(result);
 
         if (!isTesSuccess(result.ter))
         {
             if (mode & tfAllOrNothing)
-                return false;
+                return std::nullopt;
 
             if (mode & tfUntilFailure)
                 break;
@@ -192,7 +209,12 @@
             break;
     }
 
-    return applied != 0;
+    if (results.empty())
+    {
+        return std::nullopt;
+    }
+
+    return results;
 }
 
 ApplyTransactionResult
@@ -224,7 +246,7 @@
             {
                 OpenView wholeBatchView(batch_view, view);
 
-                if (applyBatchTransactions(registry, wholeBatchView, txn, j))
+                if (applyBatchTransactions(registry, wholeBatchView, txn, flags, j))
                     wholeBatchView.apply(view);
             }