Allow increasing an account's nonce without changing its state (#796)

* refactor: remove nonce increase restriction

* test: add nonce update with empty delta test

* refactor: update tx script, update comment

CHANGELOG.md

@@ -7,6 +7,7 @@
 - [BREAKING] Renamed public accessors of the `Block` struct to match the updated fields (#791).
 - [BREAKING] Changed the `TransactionArgs` to use `AdviceInputs` (#793).
 - Setters in `memory` module don't drop the setting `Word` anymore (#795).
+- [BREAKING] Increase of nonce does not require changes in account state any more (#789).
 
 ## 0.4.0 (2024-07-03)
 

miden-tx/src/tests/mod.rs

@@ -377,6 +377,66 @@ fn executed_transaction_account_delta() {
     );
 }
 
+#[test]
+fn test_empty_delta_nonce_update() {
+    let tx_context = TransactionContextBuilder::with_standard_account(
+        ACCOUNT_ID_REGULAR_ACCOUNT_UPDATABLE_CODE_OFF_CHAIN,
+        ONE,
+    )
+    .build();
+
+    let mut executor: TransactionExecutor<_, ()> =
+        TransactionExecutor::new(tx_context.clone(), None);
+    let account_id = tx_context.tx_inputs().account().id();
+    executor.load_account(account_id).unwrap();
+
+    let tx_script = format!(
+        "\
+        begin
+            push.1 
+            
+            call.{ACCOUNT_INCR_NONCE_MAST_ROOT}
+            # => [0, 1]
+            
+            drop drop
+            # => []
+        end
+    "
+    );
+    let tx_script_code = ProgramAst::parse(&tx_script).unwrap();
+    let tx_script = executor.compile_tx_script(tx_script_code, vec![], vec![]).unwrap();
+    let tx_args = TransactionArgs::new(
+        Some(tx_script),
+        None,
+        tx_context.tx_args().advice_inputs().clone().map,
+    );
+
+    let block_ref = tx_context.tx_inputs().block_header().block_num();
+    let note_ids = tx_context
+        .tx_inputs()
+        .input_notes()
+        .iter()
+        .map(|note| note.id())
+        .collect::<Vec<_>>();
+
+    // expected delta
+    // --------------------------------------------------------------------------------------------
+    // execute the transaction and get the witness
+    let executed_transaction =
+        executor.execute_transaction(account_id, block_ref, &note_ids, tx_args).unwrap();
+
+    // nonce delta
+    // --------------------------------------------------------------------------------------------
+    assert_eq!(executed_transaction.account_delta().nonce(), Some(Felt::new(2)));
+
+    // storage delta
+    // --------------------------------------------------------------------------------------------
+    // We expect one updated item and one updated map
+    assert_eq!(executed_transaction.account_delta().storage().updated_items.len(), 0);
+
+    assert_eq!(executed_transaction.account_delta().storage().updated_maps.len(), 0);
+}
+
 #[test]
 fn executed_transaction_output_notes() {
     let tx_context = TransactionContextBuilder::with_standard_account(

objects/src/accounts/delta/mod.rs

@@ -41,7 +41,6 @@ impl AccountDelta {
     /// # Errors
     /// Returns an error if:
     /// - Storage or vault deltas are invalid.
-    /// - Storage and vault deltas are empty, and the nonce was updated.
     /// - Storage or vault deltas are not empty, but nonce was not updated.
     pub fn new(
         storage: AccountStorageDelta,
@@ -52,7 +51,7 @@ impl AccountDelta {
         storage.validate()?;
         vault.validate()?;
 
-        // nonce must be updated if and only if either account storage or vault were updated
+        // nonce must be updated if either account storage or vault were updated
         validate_nonce(nonce, &storage, &vault)?;
 
         Ok(Self { storage, vault, nonce })
@@ -169,7 +168,6 @@ impl Deserializable for AccountUpdateDetails {
 /// # Errors
 /// Returns an error if:
 /// - Storage or vault were updated, but the nonce was either not updated or set to 0.
-/// - Storage and vault were not updated, but the nonce was updated.
 fn validate_nonce(
     nonce: Option<Felt>,
     storage: &AccountStorageDelta,
@@ -190,10 +188,6 @@ fn validate_nonce(
                 ))
             },
         }
-    } else if nonce.is_some() {
-        return Err(AccountDeltaError::InconsistentNonceUpdate(
-            "nonce updated for empty delta".to_string(),
-        ));
     }
 
     Ok(())
@@ -222,7 +216,7 @@ mod tests {
         };
 
         assert!(AccountDelta::new(storage_delta.clone(), vault_delta.clone(), None).is_ok());
-        assert!(AccountDelta::new(storage_delta.clone(), vault_delta.clone(), Some(ONE)).is_err());
+        assert!(AccountDelta::new(storage_delta.clone(), vault_delta.clone(), Some(ONE)).is_ok());
 
         // non-empty delta
         let storage_delta = AccountStorageDelta {

objects/src/accounts/mod.rs

@@ -481,7 +481,6 @@ mod tests {
     }
 
     #[test]
-    #[should_panic]
     fn empty_account_delta_with_incremented_nonce() {
         // build account
         let init_nonce = Felt::new(1);