Support devnet in --network flag

CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Debug logging for `sncast` commands that can be enabled by setting `CAST_LOG` env variable.
 - `sncast declare` command now outputs a ready-to-use deployment command after successful declaration.
+- Support for `--network devnet` flag that attempts to auto-detect running `starknet-devnet` instance and connect to it.
 
 ## [0.50.0] - 2025-09-29
 

crates/sncast/src/helpers/block_explorer.rs

@@ -24,6 +24,7 @@ impl Service {
             (Service::ViewBlock, Network::Mainnet) => Ok(Box::new(ViewBlock)),
             (Service::OkLink, Network::Mainnet) => Ok(Box::new(OkLink)),
             (_, Network::Sepolia) => Err(ExplorerError::SepoliaNotSupported),
+            (_, Network::Devnet) => Err(ExplorerError::DevnetNotSupported),
         }
     }
 }
@@ -36,8 +37,8 @@ pub trait LinkProvider {
 
 const fn network_subdomain(network: Network) -> &'static str {
     match network {
-        Network::Mainnet => "",
         Network::Sepolia => "sepolia.",
+        Network::Mainnet | Network::Devnet => "",
     }
 }
 

crates/sncast/src/helpers/devnet_detection.rs

@@ -0,0 +1,308 @@
+use std::process::Command;
+
+#[derive(Debug, Clone)]
+struct DevnetInfo {
+    host: String,
+    port: u16,
+}
+
+#[derive(Debug)]
+enum FindDevnetError {
+    None,
+    Multiple,
+    CommandFailed,
+}
+
+pub fn detect_devnet_url() -> Result<String, String> {
+    detect_devnet_from_processes()
+}
+
+#[must_use]
+pub fn is_devnet_running() -> bool {
+    detect_devnet_from_processes().is_ok()
+}
+
+fn detect_devnet_from_processes() -> Result<String, String> {
+    match find_devnet_process_info() {
+        Ok(info) => Ok(format!("http://{}:{}", info.host, info.port)),
+        Err(FindDevnetError::Multiple) => {
+            Err("Multiple starknet-devnet instances found. Please use --url to specify which one to use.".to_string())
+        }
+        Err(FindDevnetError::None | FindDevnetError::CommandFailed) => {
+            // Fallback to default starknet-devnet URL if reachable
+            if is_port_reachable("127.0.0.1", 5050) {
+                Ok("http://127.0.0.1:5050".to_string())
+            } else {
+                Err("Could not detect running starknet-devnet instance. Please use --url instead.".to_string())
+            }
+        }
+    }
+}
+
+fn find_devnet_process_info() -> Result<DevnetInfo, FindDevnetError> {
+    let output = Command::new("ps")
+        .args(["aux"])
+        .output()
+        .map_err(|_| FindDevnetError::CommandFailed)?;
+    let ps_output = String::from_utf8_lossy(&output.stdout);
+
+    let devnet_processes: Vec<DevnetInfo> = ps_output
+        .lines()
+        .filter(|line| line.contains("starknet-devnet"))
+        .map(|line| {
+            if line.contains("docker") || line.contains("podman") {
+                extract_devnet_info_from_docker_line(line)
+            } else {
+                extract_devnet_info_from_cmdline(line)
+            }
+        })
+        .collect();
+
+    match devnet_processes.as_slice() {
+        [] => Err(FindDevnetError::None),
+        [single] => Ok(single.clone()),
+        _ => Err(FindDevnetError::Multiple),
+    }
+}
+
+fn extract_string_from_flag(cmdline: &str, flag: &str) -> Option<String> {
+    if let Some(pos) = cmdline.find(flag) {
+        let after_pattern = &cmdline[pos + flag.len()..];
+        let value_str = after_pattern
+            .split_whitespace()
+            .next()
+            .unwrap_or("")
+            .trim_start_matches('=')
+            .trim_start_matches(':');
+
+        if !value_str.is_empty() {
+            return Some(value_str.to_string());
+        }
+    }
+    None
+}
+
+fn extract_port_from_flag(cmdline: &str, flag: &str) -> Option<u16> {
+    if let Some(port_str) = extract_string_from_flag(cmdline, flag)
+        && let Ok(p) = port_str.parse::<u16>()
+        && p > 1024
+        && p < 65535
+    {
+        return Some(p);
+    }
+
+    None
+}
+
+fn extract_docker_port_mapping(cmdline: &str) -> Option<(String, u16)> {
+    if let Some(pos) = cmdline.find("-p ") {
+        let after_pattern = &cmdline[pos + 3..]; // "-p ".len() = 3
+        let port_mapping = after_pattern.split_whitespace().next().unwrap_or("");
+
+        let parts: Vec<&str> = port_mapping.split(':').collect();
+        if parts.len() == 3
+            && let Ok(external_port) = parts[1].parse::<u16>()
+        {
+            return Some((parts[0].to_string(), external_port));
+        } else if parts.len() == 2
+            && let Ok(external_port) = parts[0].parse::<u16>()
+        {
+            return Some(("127.0.0.1".to_string(), external_port));
+        }
+    }
+    None
+}
+
+fn extract_devnet_info_from_docker_line(cmdline: &str) -> DevnetInfo {
+    let mut port = None;
+    let mut host = None;
+
+    if let Some((docker_host, docker_port)) = extract_docker_port_mapping(cmdline) {
+        host = Some(docker_host);
+        port = Some(docker_port);
+    }
+
+    if port.is_none() {
+        port = extract_port_from_flag(cmdline, "--port");
+    }
+
+    let final_host = host.unwrap_or_else(|| "127.0.0.1".to_string());
+    let final_port = port.unwrap_or(5050);
+
+    DevnetInfo {
+        host: final_host,
+        port: final_port,
+    }
+}
+
+fn extract_devnet_info_from_cmdline(cmdline: &str) -> DevnetInfo {
+    let mut port = extract_port_from_flag(cmdline, "--port");
+    let mut host = extract_string_from_flag(cmdline, "--host");
+
+    if port.is_none()
+        && let Ok(port_env) = std::env::var("PORT")
+        && let Ok(p) = port_env.parse::<u16>()
+        && p > 1024
+        && p < 65535
+    {
+        port = Some(p);
+    }
+
+    if host.is_none()
+        && let Ok(host_env) = std::env::var("HOST")
+        && !host_env.is_empty()
+    {
+        host = Some(host_env);
+    }
+
+    let final_port = port.unwrap_or(5050);
+    let final_host = host.unwrap_or_else(|| "127.0.0.1".to_string());
+
+    DevnetInfo {
+        host: final_host,
+        port: final_port,
+    }
+}
+
+fn is_port_reachable(host: &str, port: u16) -> bool {
+    let url = format!("http://{host}:{port}/is_alive");
+
+    // TODO: Try to use a DevnetProvider::ensure_alive() from https://github.com/foundry-rs/starknet-foundry/blob/master/crates/sncast/src/helpers/devnet_provider.rs#L82
+    std::process::Command::new("curl")
+        .args(["-s", "-f", "--max-time", "1", &url])
+        .output()
+        .map(|output| output.status.success())
+        .unwrap_or(false)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::process::{Command, Stdio};
+    use std::thread;
+    use std::time::{Duration, Instant};
+
+    // These tests are marked to run serially to avoid interference from environment variables
+    #[test]
+    fn test_devnet_parsing() {
+        test_extract_devnet_info_from_cmdline();
+
+        test_extract_devnet_info_from_docker_line();
+
+        test_extract_devnet_info_with_both_envs();
+
+        test_cmdline_args_override_env();
+
+        test_detect_devnet_url();
+    }
+
+    fn test_extract_devnet_info_from_cmdline() {
+        let cmdline1 = "starknet-devnet --port 5050 --host 127.0.0.1";
+        let info1 = extract_devnet_info_from_cmdline(cmdline1);
+        assert_eq!(info1.port, 5050);
+        assert_eq!(info1.host, "127.0.0.1");
+
+        let cmdline2 = "/usr/bin/starknet-devnet --port=5000";
+        let info2 = extract_devnet_info_from_cmdline(cmdline2);
+        assert_eq!(info2.port, 5000);
+        assert_eq!(info2.host, "127.0.0.1");
+
+        let cmdline3 = "starknet-devnet --host 127.0.0.1";
+        let info3 = extract_devnet_info_from_cmdline(cmdline3);
+        assert_eq!(info3.port, 5050);
+        assert_eq!(info3.host, "127.0.0.1");
+    }
+
+    fn test_extract_devnet_info_from_docker_line() {
+        let cmdline1 = "docker run -p 127.0.0.1:5055:5050 shardlabs/starknet-devnet-rs";
+        let info1 = extract_devnet_info_from_docker_line(cmdline1);
+        assert_eq!(info1.port, 5055);
+        assert_eq!(info1.host, "127.0.0.1");
+
+        let cmdline2 = "docker run -p 8080:5050 shardlabs/starknet-devnet-rs";
+        let info2 = extract_devnet_info_from_docker_line(cmdline2);
+        assert_eq!(info2.port, 8080);
+        assert_eq!(info2.host, "127.0.0.1");
+
+        let cmdline3 = "docker run --network host shardlabs/starknet-devnet-rs --port 5055";
+        let info3 = extract_devnet_info_from_docker_line(cmdline3);
+        assert_eq!(info3.port, 5055);
+        assert_eq!(info3.host, "127.0.0.1");
+    }
+
+    fn test_extract_devnet_info_with_both_envs() {
+        // SAFETY: Variables are only modified within this test and cleaned up afterwards
+        unsafe {
+            std::env::set_var("PORT", "9999");
+            std::env::set_var("HOST", "9.9.9.9");
+        }
+
+        let cmdline = "starknet-devnet";
+        let info = extract_devnet_info_from_cmdline(cmdline);
+        assert_eq!(info.port, 9999);
+        assert_eq!(info.host, "9.9.9.9");
+
+        // SAFETY: Clean up environment variables to prevent interference
+        unsafe {
+            std::env::remove_var("PORT");
+            std::env::remove_var("HOST");
+        }
+    }
+
+    fn test_cmdline_args_override_env() {
+        // SAFETY: Variables are only modified within this test and cleaned up afterwards
+        unsafe {
+            std::env::set_var("PORT", "3000");
+            std::env::set_var("HOST", "7.7.7.7");
+        }
+
+        let cmdline = "starknet-devnet --port 9999 --host 192.168.1.1";
+        let info = extract_devnet_info_from_cmdline(cmdline);
+        assert_eq!(info.port, 9999);
+        assert_eq!(info.host, "192.168.1.1");
+
+        // SAFETY: Clean up environment variables to prevent interference
+        unsafe {
+            std::env::remove_var("PORT");
+            std::env::remove_var("HOST");
+        }
+    }
+
+    fn test_detect_devnet_url() {
+        let child = spawn_devnet("5090");
+
+        let result = detect_devnet_url().expect("Failed to detect devnet URL");
+        assert_eq!(result, "http://127.0.0.1:5090");
+
+        cleanup_process(child);
+    }
+
+    fn spawn_devnet(port: &str) -> std::process::Child {
+        let mut child = Command::new("starknet-devnet")
+            .args(["--port", port])
+            .stdout(Stdio::null())
+            .stderr(Stdio::null())
+            .spawn()
+            .expect("Failed to spawn starknet-devnet process");
+
+        let port_num: u16 = port.parse().expect("Invalid port number");
+        let start_time = Instant::now();
+        let timeout = Duration::from_secs(10);
+
+        while start_time.elapsed() < timeout {
+            if is_port_reachable("127.0.0.1", port_num) {
+                return child;
+            }
+            thread::sleep(Duration::from_millis(500));
+        }
+
+        let _ = child.kill();
+        let _ = child.wait();
+        panic!("Devnet did not start in time on port {port}");
+    }
+
+    fn cleanup_process(mut child: std::process::Child) {
+        child.kill().expect("Failed to kill devnet process");
+        child.wait().expect("Failed to wait for devnet process");
+    }
+}

crates/sncast/src/helpers/mod.rs

@@ -5,6 +5,7 @@ pub mod command;
 pub mod config;
 pub mod configuration;
 pub mod constants;
+pub mod devnet_detection;
 pub mod devnet_provider;
 pub mod fee;
 pub mod interactive;