add write_output_to_file func to cairo-program-runner-lib (#269)

## Type

- [ ] feature
- [ ] bugfix
- [ ] dev (no functional changes, no API changes)
- [ ] fmt (formatting, renaming)
- [ ] build
- [ ] docs
- [ ] testing

## Description


## Breaking changes?

- [ ] yes
- [ ] no

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- - -
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Author: nitsan-starkware

crates/cairo-program-runner-lib/Cargo.toml

@@ -5,6 +5,7 @@ edition = "2021"
 
 
 [dependencies]
+anyhow.workspace = true
 bincode.workspace = true
 cairo-vm.workspace = true
 cairo-lang-executable.workspace = true
@@ -17,6 +18,7 @@ num-traits.workspace = true
 regex.workspace = true
 serde.workspace = true
 serde_json.workspace = true
+sonic-rs.workspace = true
 starknet-crypto.workspace = true
 starknet-types-core.workspace = true
 thiserror.workspace = true

crates/cairo-program-runner-lib/src/utils.rs

@@ -9,6 +9,8 @@ use cairo_vm::{
         errors::program_errors::ProgramError, layout::CairoLayoutParams, layout_name::LayoutName,
         program::Program,
     },
+    vm::runners::cairo_runner::CairoRunner,
+    Felt252,
 };
 
 use crate::types::RunMode;
@@ -115,3 +117,18 @@ pub fn get_cairo_run_config(
         .create_config()
     })
 }
+
+/// Write the program output to the specified output path as Felt252 values.
+pub fn write_output_to_file(runner: &mut CairoRunner, output_path: PathBuf) -> anyhow::Result<()> {
+    let mut output_buffer = String::new();
+    runner.vm.write_output(&mut output_buffer)?;
+    let output_lines = output_buffer
+        .lines()
+        .map(|line| {
+            Felt252::from_dec_str(line)
+                .map_err(|_| anyhow::anyhow!("Failed to parse output line as Felt decimal: {line}"))
+        })
+        .collect::<Result<Vec<Felt252>, anyhow::Error>>()?;
+    std::fs::write(&output_path, sonic_rs::to_string_pretty(&output_lines)?)?;
+    Ok(())
+}

crates/cairo-program-runner/src/bin/cairo_program_runner/main.rs

@@ -4,12 +4,14 @@ use std::io::{self, Write};
 use std::path::PathBuf;
 
 use bincode::enc::write::Writer;
-use cairo_program_runner_lib::utils::{get_cairo_run_config, get_program, get_program_input};
+use cairo_program_runner_lib::utils::{
+    get_cairo_run_config, get_program, get_program_input, write_output_to_file,
+};
 use cairo_vm::types::layout_name::LayoutName;
 
 use cairo_program_runner_lib::cairo_run_program;
+use cairo_vm::cairo_run;
 use cairo_vm::vm::errors::cairo_run_errors::CairoRunError;
-use cairo_vm::{cairo_run, Felt252};
 use clap::Parser;
 use tempfile::NamedTempFile;
 
@@ -167,16 +169,7 @@ fn main() -> Result<(), Box<dyn Error>> {
 
     // Handle program output file if specified
     if let Some(outputs_file) = args.outputs_file {
-        let mut output_buffer = String::new();
-        runner.vm.write_output(&mut output_buffer)?;
-        let output_lines = output_buffer
-            .lines()
-            .map(|line| {
-                Felt252::from_dec_str(line)
-                    .map_err(|_| format!("Failed to parse output line as Felt decimal: {line}"))
-            })
-            .collect::<Result<Vec<Felt252>, _>>()?;
-        std::fs::write(outputs_file, serde_json::to_string_pretty(&output_lines)?)?;
+        write_output_to_file(&mut runner, outputs_file)?;
     }
 
     // Handle execution resources file if specified

crates/stwo_run_and_prove/src/main.rs

@@ -1,14 +1,14 @@
 use anyhow::Result;
 use cairo_air::utils::ProofFormat;
 use cairo_program_runner_lib::cairo_run_program;
-use cairo_program_runner_lib::utils::{get_cairo_run_config, get_program, get_program_input};
-use cairo_vm::Felt252;
+use cairo_program_runner_lib::utils::{
+    get_cairo_run_config, get_program, get_program_input, write_output_to_file,
+};
 use cairo_vm::types::errors::program_errors::ProgramError;
 use cairo_vm::types::layout_name::LayoutName;
 use cairo_vm::vm::errors::cairo_run_errors::CairoRunError;
 use cairo_vm::vm::errors::runner_errors::RunnerError;
 use cairo_vm::vm::errors::vm_errors::VirtualMachineError;
-use cairo_vm::vm::runners::cairo_runner::CairoRunner;
 use clap::Parser;
 #[cfg(test)]
 use mockall::automock;
@@ -87,8 +87,6 @@ enum StwoRunAndProveError {
     Serializing(#[from] sonic_rs::error::Error),
     #[error(transparent)]
     VM(#[from] VirtualMachineError),
-    #[error("Failed to parse output line as Felt decimal.")]
-    OutputParsing,
     #[error(transparent)]
     Anyhow(#[from] anyhow::Error),
 }
@@ -167,7 +165,7 @@ fn stwo_run_and_prove(
         .map_err(|e| StwoRunAndProveError::Program(e, program_path))?;
     let program_input = get_program_input(&program_input)
         .map_err(|e| StwoRunAndProveError::PathIO(e, program_input.unwrap_or_default()))?;
-    let runner = cairo_run_program(&program, program_input, cairo_run_config)?;
+    let mut runner = cairo_run_program(&program, program_input, cairo_run_config)?;
     let prover_input = adapt(&runner)?;
     let result = prove(prover_input.clone(), prove_config, prover);
 
@@ -187,7 +185,8 @@ fn stwo_run_and_prove(
     if let Some(output_path) = program_output
         && result.is_ok()
     {
-        write_output_to_file(runner, output_path)?;
+        info!("Saving program output to: {:?}", output_path);
+        write_output_to_file(&mut runner, output_path)?;
     }
 
     result
@@ -262,28 +261,6 @@ impl ProverTrait for StwoProverEntryPoint {
     }
 }
 
-/// Write the program output to the specified output path as Felt252 values.
-fn write_output_to_file(
-    mut runner: CairoRunner,
-    output_path: PathBuf,
-) -> Result<(), StwoRunAndProveError> {
-    info!("Saving program output to: {:?}", output_path);
-    // TODO(Nitsan): move this function to cairo_program_runner_lib or a new utils lib,
-    // and call it from here and from cairo_program_runner.
-
-    let mut output_buffer = String::new();
-    runner.vm.write_output(&mut output_buffer)?;
-    let output_lines = output_buffer
-        .lines()
-        .map(|line: &str| {
-            Felt252::from_dec_str(line).map_err(|_| StwoRunAndProveError::OutputParsing)
-        })
-        .collect::<Result<Vec<Felt252>, _>>()?;
-    std::fs::write(&output_path, sonic_rs::to_string_pretty(&output_lines)?)
-        .map_err(|e| StwoRunAndProveError::PathIO(e, output_path))?;
-    Ok(())
-}
-
 fn file_empty(path: &PathBuf) -> std::io::Result<bool> {
     let metadata = fs::metadata(path)?;
     Ok(metadata.len() == 0)
@@ -303,6 +280,7 @@ fn file_missing_or_empty(path: &PathBuf) -> std::io::Result<bool> {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use cairo_vm::Felt252;
     use ctor::ctor;
     use serde_json::Value;
     use stwo_cairo_utils::logging_utils::init_logging;