feat!: prevent implicit burn (#1562)

# Summary
TransactionBuilder will return an error on `.build()` if the transaction
has input assets that don't have a corresponding change output. To
enable burning, `.enable_burn()` flag has to be set to `true`.

# Breaking Changes
Building transactions that implicitly burn coins will result in an
error.
`adjust_for_fee` will add a base asset output consistently

# Checklist

- [x] All **changes** are **covered** by **tests** (or not applicable)
- [ ] All **changes** are **documented** (or not applicable)
- [x] I **reviewed** the **entire PR** myself (preferably, on GH UI)
- [x] I **described** all **Breaking Changes** (or there's none)

e2e/tests/contracts.rs

@@ -2,7 +2,7 @@ use std::time::Duration;
 
 use fuel_tx::{
     consensus_parameters::{ConsensusParametersV1, FeeParametersV1},
-    ConsensusParameters, FeeParameters,
+    ConsensusParameters, FeeParameters, Output,
 };
 use fuels::{
     core::codec::{calldata, encode_fn_selector, DecoderConfig, EncoderConfig},
@@ -1707,12 +1707,16 @@ async fn contract_custom_call_no_signatures_strategy() -> Result<()> {
 
     let mut tb = call_handler.transaction_builder().await?;
 
+    let base_asset_id = *provider.consensus_parameters().await?.base_asset_id();
+
     let amount = 10;
     let consensus_parameters = provider.consensus_parameters().await?;
     let new_base_inputs = wallet
-        .get_asset_inputs_for_amount(*consensus_parameters.base_asset_id(), amount, None)
+        .get_asset_inputs_for_amount(base_asset_id, amount, None)
         .await?;
     tb.inputs_mut().extend(new_base_inputs);
+    tb.outputs_mut()
+        .push(Output::change(wallet.address().into(), 0, base_asset_id));
 
     // ANCHOR: tb_no_signatures_strategy
     let mut tx = tb

e2e/tests/predicates.rs

@@ -809,6 +809,7 @@ async fn predicate_adjust_fee_persists_message_w_data() -> Result<()> {
         TxPolicies::default().with_tip(1),
     );
     predicate.adjust_for_fee(&mut tb, 1000).await?;
+
     let tx = tb.build(&provider).await?;
 
     assert_eq!(tx.inputs().len(), 2);

e2e/tests/scripts.rs

@@ -1,5 +1,6 @@
 use std::time::Duration;
 
+use fuel_tx::Output;
 use fuels::{
     core::{
         codec::{DecoderConfig, EncoderConfig},
@@ -132,8 +133,10 @@ async fn test_output_variable_estimation() -> Result<()> {
     let inputs = wallet
         .get_asset_inputs_for_amount(asset_id, amount, None)
         .await?;
+    let output = Output::change(wallet.address().into(), 0, asset_id);
     let _ = script_call
         .with_inputs(inputs)
+        .with_outputs(vec![output])
         .with_variable_output_policy(VariableOutputPolicy::EstimateMinimum)
         .call()
         .await?;

packages/fuels-accounts/src/account.rs

@@ -19,7 +19,7 @@ use fuels_core::types::{
 
 use crate::{
     accounts_utils::{
-        adjust_inputs_outputs, available_base_assets_and_amount, calculate_missing_base_amount,
+        add_base_change_if_needed, available_base_assets_and_amount, calculate_missing_base_amount,
         extract_message_nonce, split_into_utxo_ids_and_nonces,
     },
     provider::{Provider, ResourceFilter},
@@ -117,7 +117,8 @@ pub trait ViewOnlyAccount: std::fmt::Debug + Send + Sync + Clone {
         excluded_coins: Option<Vec<CoinTypeId>>,
     ) -> Result<Vec<Input>>;
 
-    /// Add base asset inputs to the transaction to cover the estimated fee.
+    /// Add base asset inputs to the transaction to cover the estimated fee
+    /// and add a change output for the base asset if needed.
     /// Requires contract inputs to be at the start of the transactions inputs vec
     /// so that their indexes are retained
     async fn adjust_for_fee<Tb: TransactionBuilder + Sync>(
@@ -141,14 +142,11 @@ pub trait ViewOnlyAccount: std::fmt::Debug + Send + Sync + Clone {
                 )
                 .await?;
 
-            adjust_inputs_outputs(
-                tb,
-                new_base_inputs,
-                self.address(),
-                consensus_parameters.base_asset_id(),
-            );
+            tb.inputs_mut().extend(new_base_inputs);
         };
 
+        add_base_change_if_needed(tb, self.address(), consensus_parameters.base_asset_id());
+
         Ok(())
     }
 }
@@ -407,10 +405,11 @@ mod tests {
                 1,
                 Default::default(),
             );
+            let change = Output::change(wallet.address().into(), 0, Default::default());
 
             ScriptTransactionBuilder::prepare_transfer(
                 vec![input_coin],
-                vec![output_coin],
+                vec![output_coin, change],
                 Default::default(),
             )
         };
@@ -433,7 +432,7 @@ mod tests {
         assert_eq!(signature, tx_signature);
 
         // Check if the signature is what we expect it to be
-        assert_eq!(signature, Signature::from_str("8afd30de7039faa07aac1cf2676970a77dc8ef3f779b44c1510ad7bf58ea56f43727b23142bd7252b79ae2c832e073927f84f6b0857fedf2f6d86e9535e48fd0")?);
+        assert_eq!(signature, Signature::from_str("faa616776a1c336ef6257f7cb0cb5cd932180e2d15faba5f17481dae1cbcaf314d94617bd900216a6680bccb1ea62438e4ca93b0d5733d33788ef9d79cc24e9f")?);
 
         // Recover the address that signed the transaction
         let recovered_address = signature.recover(&message)?;

packages/fuels-accounts/src/accounts_utils.rs

@@ -90,14 +90,11 @@ fn is_consuming_utxos(tb: &impl TransactionBuilder) -> bool {
         .any(|input| !matches!(input, Input::Contract { .. }))
 }
 
-pub fn adjust_inputs_outputs(
+pub fn add_base_change_if_needed(
     tb: &mut impl TransactionBuilder,
-    new_base_inputs: impl IntoIterator<Item = Input>,
     address: &Bech32Address,
     base_asset_id: &AssetId,
 ) {
-    tb.inputs_mut().extend(new_base_inputs);
-
     let is_base_change_present = tb.outputs().iter().any(|output| {
         matches!(output , Output::Change { asset_id , .. }
                                         if asset_id == base_asset_id)