Write to output when no casm_output_path provided

Cargo.toml

@@ -10,7 +10,6 @@ cairo-lang-starknet-sierra-1_0_0 = { package = "cairo-lang-starknet", git = "htt
 cairo-lang-starknet = "=2.4.0"
 serde_json = "1.0.108"
 serde = "1.0.193"
-test-case = "3.3.1"
 clap = "4.4.11"
 anyhow = "1.0.75"
 console = "0.15.7"
@@ -20,6 +19,7 @@ snapbox = "0.4.15"
 tempfile = "3.8.1"
 indoc = "2.0.4"
 fs_extra = "1.3.0"
+test-case = "3.3.1"
 
 [[bin]]
 name = "universal-sierra-compiler"

src/main.rs

@@ -2,7 +2,7 @@ use anyhow::{Context, Error, Result};
 use clap::Parser;
 use console::style;
 use serde_json::to_writer;
-use std::fs::{File, OpenOptions};
+use std::fs::File;
 use std::path::PathBuf;
 use universal_sierra_compiler::compile;
 
@@ -15,7 +15,7 @@ struct Args {
 
     /// Path to where casm json file will be saved
     #[arg(short, long)]
-    casm_output_path: PathBuf,
+    casm_output_path: Option<PathBuf>,
 }
 
 fn print_error_message(error: &Error) {
@@ -34,14 +34,17 @@ fn main_execution() -> Result<bool> {
     let casm = compile(sierra_json)?;
     let casm_json = serde_json::to_value(casm)?;
 
-    let casm_file = OpenOptions::new()
-        .write(true)
-        .create(true)
-        .append(false)
-        .open(args.casm_output_path)
-        .context("Unable to open/create casm json file")?;
+    match args.casm_output_path {
+        Some(output_path) => {
+            let casm_file =
+                File::create(output_path).context("Unable to open/create casm json file")?;
 
-    to_writer(casm_file, &casm_json).context("Unable to save casm json file")?;
+            to_writer(casm_file, &casm_json).context("Unable to save casm json file")?;
+        }
+        None => {
+            println!("{}", serde_json::to_string(&casm_json)?);
+        }
+    };
 
     Ok(true)
 }

tests/e2e.rs

@@ -57,6 +57,18 @@ fn write_to_existing_file() {
     verify_output_file(temp_dir.path().join(casm_file_name));
 }
 
+#[test]
+fn write_to_stdout() {
+    let sierra_file_name = "sierra_1_4_0.json";
+    let args = vec!["--sierra-input-path", &sierra_file_name];
+
+    let temp_dir = temp_dir_with_sierra_file(sierra_file_name);
+    let snapbox = runner(args, &temp_dir);
+
+    let output = String::from_utf8(snapbox.assert().success().get_output().stdout.clone()).unwrap();
+    assert!(output.contains("bytecode"));
+}
+
 #[test]
 fn wrong_json() {
     let sierra_file_name = "wrong_sierra.json";