fix: forc-call variable output default estimation with override (#7384)

## Description

When using `forc-call` with a large `--amount`, the transaction
incorrectly sets output count equal to the amount value (e.g.,
transferring 1000 units creates 1000 outputs).

### Solution
- Added `--variable-output` parameter to explicitly control output count
- Changed default behavior to estimate minimum outputs via dry-run
instead of using using amount value as UTXO outputs
- Improved type safety by changing `script_json: serde_json::Value` to
`script: fuel_tx::Script`

## Testing
- Updated tests to verify correct output counts
- Added assertions to check `script.outputs().len()` matches
expectations
- Tests confirm behavior in both dry-run and live execution modes

Addresses: #7383

## Checklist

- [x] I have linked to any relevant issues.
- [x] I have commented my code, particularly in hard-to-understand
areas.
- [ ] I have updated the documentation where relevant (API docs, the
reference, and the Sway book).
- [ ] If my change requires substantial documentation changes, I have
[requested support from the DevRel
team](https://github.com/FuelLabs/devrel-requests/issues/new/choose)
- [x] I have added tests that prove my fix is effective or that my
feature works.
- [x] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [x] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [x] I have requested a review from the relevant team or maintainers.

---------

Co-authored-by: z <zees-dev@users.noreply.github.com>

Author: zees-dev

forc-plugins/forc-client/src/cmd/call.rs

@@ -419,6 +419,10 @@ pub struct Command {
     #[clap(long, short = 'o', default_value = "default", help_heading = "OUTPUT")]
     pub output: OutputFormat,
 
+    /// Contract call variable output count
+    #[clap(long, alias = "variable-output", help_heading = "VARIABLE OUTPUT")]
+    pub variable_output: Option<usize>,
+
     /// Set verbosity levels; currently only supports max 2 levels
     /// - `-v=1`: Print decoded logs
     /// - `-v=2`: Additionally print receipts and script json

forc-plugins/forc-client/src/op/call/call_function.rs

@@ -50,6 +50,7 @@ pub async fn call_function(
         mut output,
         external_contracts,
         contract_abis,
+        variable_output,
         ..
     } = cmd;
 
@@ -88,7 +89,9 @@ pub async fn call_function(
     };
 
     // Setup variable output policy and log decoder
-    let variable_output_policy = VariableOutputPolicy::Exactly(call_parameters.amount as usize);
+    let variable_output_policy = variable_output
+        .map(VariableOutputPolicy::Exactly)
+        .unwrap_or(VariableOutputPolicy::EstimateMinimum);
     let error_codes = abi
         .unified
         .error_codes
@@ -275,8 +278,6 @@ pub async fn call_function(
     let fuel_tx::Transaction::Script(script) = &tx else {
         bail!("Transaction is not a script");
     };
-    let script_json = serde_json::to_value(script)
-        .map_err(|e| anyhow!("Failed to convert script to JSON: {e}"))?;
 
     // Parse the result based on output format
     let mut receipt_parser =
@@ -330,7 +331,7 @@ pub async fn call_function(
 
         super::display_detailed_call_info(
             &tx_execution,
-            &script_json,
+            script,
             &abi_map,
             cmd.verbosity,
             &mut output,
@@ -357,7 +358,7 @@ pub async fn call_function(
         result: Some(result),
         total_gas: *tx_execution.result.total_gas(),
         receipts: tx_execution.result.receipts().to_vec(),
-        script_json: Some(script_json),
+        script: Some(script.to_owned()),
         trace_events,
     })
 }
@@ -466,6 +467,7 @@ pub mod tests {
         cmd,
         op::call::{call, get_wallet, PrivateKeySigner},
     };
+    use fuel_tx::field::Outputs;
     use fuels::{crypto::SecretKey, prelude::*};
     use std::path::PathBuf;
 
@@ -493,6 +495,7 @@ pub mod tests {
             label: None,
             output: cmd::call::OutputFormat::Raw,
             list_functions: false,
+            variable_output: None,
             verbosity: 0,
             debug: false,
         }
@@ -948,15 +951,9 @@ pub mod tests {
             gas_forwarded: None,
         };
         // validate balance is unchanged (dry-run)
-        assert_eq!(
-            call(operation.clone(), cmd.clone())
-                .await
-                .unwrap()
-                .result
-                .unwrap(),
-            "()"
-        );
-        assert_eq!(get_contract_balance(id_2, provider.clone()).await, 0);
+        let call_response = call(operation.clone(), cmd.clone()).await.unwrap();
+        assert_eq!(call_response.result.unwrap(), "()");
+        assert_eq!(call_response.script.unwrap().outputs().len(), 2);
         cmd.mode = cmd::call::ExecutionMode::Live;
         assert_eq!(call(operation, cmd).await.unwrap().result.unwrap(), "()");
         assert_eq!(get_contract_balance(id_2, provider.clone()).await, 1);
@@ -983,7 +980,9 @@ pub mod tests {
         };
         cmd.mode = cmd::call::ExecutionMode::Live;
         let operation = cmd.validate_and_get_operation().unwrap();
-        assert_eq!(call(operation, cmd).await.unwrap().result.unwrap(), "()");
+        let call_response = call(operation, cmd).await.unwrap();
+        assert_eq!(call_response.result.unwrap(), "()");
+        assert_eq!(call_response.script.unwrap().outputs().len(), 3);
         assert_eq!(
             get_recipient_balance(random_wallet.address(), provider.clone()).await,
             2
@@ -1041,7 +1040,9 @@ pub mod tests {
         };
         cmd.mode = cmd::call::ExecutionMode::Live;
         let operation = cmd.validate_and_get_operation().unwrap();
-        assert_eq!(call(operation, cmd).await.unwrap().result.unwrap(), "()");
+        let call_response = call(operation, cmd).await.unwrap();
+        assert_eq!(call_response.result.unwrap(), "()");
+        assert_eq!(call_response.script.unwrap().outputs().len(), 3);
         assert_eq!(
             get_recipient_balance(random_wallet.address(), provider.clone()).await,
             3

forc-plugins/forc-client/src/op/call/mod.rs

@@ -45,7 +45,7 @@ pub struct CallResponse {
     #[serde(skip_serializing_if = "Vec::is_empty")]
     pub trace_events: Vec<trace::TraceEvent>,
     #[serde(rename = "Script", skip_serializing_if = "Option::is_none")]
-    pub script_json: Option<serde_json::Value>,
+    pub script: Option<fuel_tx::Script>,
 }
 
 /// A command for calling a contract function.
@@ -266,7 +266,7 @@ pub(crate) fn display_tx_info(
 /// Prints receipts and trace to the writer based on verbosity level
 pub(crate) fn display_detailed_call_info(
     tx: &TransactionExecutionStatus,
-    script_json: &serde_json::Value,
+    script: &fuel_tx::Script,
     abis: &HashMap<ContractId, Abi>,
     verbosity: u8,
     writer: &mut impl std::io::Write,
@@ -276,7 +276,7 @@ pub(crate) fn display_detailed_call_info(
     if verbosity >= 4 {
         forc_tracing::println_label_green(
             "transaction script:\n",
-            &serde_json::to_string_pretty(script_json).unwrap(),
+            &serde_json::to_string_pretty(script).unwrap(),
         );
     }
     if verbosity >= 3 {

forc-plugins/forc-client/src/op/call/transfer.rs

@@ -48,7 +48,7 @@ pub async fn transfer(
         total_gas: tx_response.tx_status.total_gas,
         result: None,
         receipts: tx_response.tx_status.receipts,
-        script_json: None,
+        script: None,
         trace_events: vec![],
     })
 }

forc-plugins/forc-mcp/src/forc_call/mod.rs

@@ -540,6 +540,7 @@ fn build_call_command(
         gas,
         external_contracts: None,
         output: OutputFormat::Json,
+        variable_output: None,
         verbosity,
         debug: false,
     })
@@ -582,6 +583,7 @@ fn build_list_command(contract_id: &str, abi: &str) -> anyhow::Result<forc_clien
         gas: None,
         external_contracts: None,
         output: OutputFormat::Default,
+        variable_output: None,
         verbosity: 0,
         debug: false,
     })
@@ -641,6 +643,7 @@ fn build_transfer_command(
         gas: None,
         external_contracts: None,
         output: OutputFormat::Json,
+        variable_output: None,
         verbosity,
         debug: false,
     })