tests: handle errors properly in examples (tokio-rs#748)

Author: liranringel

examples/chat-combinator.rs

@@ -34,12 +34,12 @@ use std::env;
 use std::io::{BufReader};
 use std::sync::{Arc, Mutex};
 
-fn main() {
+fn main() -> Result<(), Box<std::error::Error>> {
     // Create the TCP listener we'll accept connections on.
     let addr = env::args().nth(1).unwrap_or("127.0.0.1:8080".to_string());
-    let addr = addr.parse().unwrap();
+    let addr = addr.parse()?;
 
-    let socket = TcpListener::bind(&addr).unwrap();
+    let socket = TcpListener::bind(&addr)?;
     println!("Listening on: {}", addr);
 
     // This is running on the Tokio runtime, so it will be multi-threaded. The
@@ -49,10 +49,10 @@ fn main() {
     // The server task asynchronously iterates over and processes each incoming
     // connection.
     let srv = socket.incoming()
-        .map_err(|e| println!("failed to accept socket; error = {:?}", e))
+        .map_err(|e| {println!("failed to accept socket; error = {:?}", e); e})
         .for_each(move |stream| {
             // The client's socket address
-            let addr = stream.peer_addr().unwrap();
+            let addr = stream.peer_addr()?;
 
             println!("New Connection: {}", addr);
 
@@ -143,8 +143,10 @@ fn main() {
             }));
 
             Ok(())
-        });
+        })
+        .map_err(|err| println!("error occurred: {:?}", err));
 
     // execute server
     tokio::run(srv);
+    Ok(())
 }

examples/chat.rs

@@ -426,20 +426,20 @@ fn process(socket: TcpStream, state: Arc<Mutex<Shared>>) {
     tokio::spawn(connection);
 }
 
-pub fn main() {
+pub fn main() -> Result<(), Box<std::error::Error>> {
     // Create the shared state. This is how all the peers communicate.
     //
     // The server task will hold a handle to this. For every new client, the
     // `state` handle is cloned and passed into the task that processes the
     // client connection.
     let state = Arc::new(Mutex::new(Shared::new()));
 
-    let addr = "127.0.0.1:6142".parse().unwrap();
+    let addr = "127.0.0.1:6142".parse()?;
 
     // Bind a TCP listener to the socket address.
     //
     // Note that this is the Tokio TcpListener, which is fully async.
-    let listener = TcpListener::bind(&addr).unwrap();
+    let listener = TcpListener::bind(&addr)?;
 
     // The server task asynchronously iterates over and processes each
     // incoming connection.
@@ -471,4 +471,5 @@ pub fn main() {
     // In our example, we have not defined a shutdown strategy, so this will
     // block until `ctrl-c` is pressed at the terminal.
     tokio::run(server);
+    Ok(())
 }

examples/connect.rs

@@ -29,7 +29,7 @@ use std::thread;
 use tokio::prelude::*;
 use futures::sync::mpsc;
 
-fn main() {
+fn main() -> Result<(), Box<std::error::Error>> {
     // Determine if we're going to run in TCP or UDP mode
     let mut args = env::args().skip(1).collect::<Vec<_>>();
     let tcp = match args.iter().position(|a| a == "--udp") {
@@ -41,26 +41,27 @@ fn main() {
     };
 
     // Parse what address we're going to connect to
-    let addr = args.first().unwrap_or_else(|| {
-        panic!("this program requires at least one argument")
-    });
-    let addr = addr.parse::<SocketAddr>().unwrap();
+    let addr = match args.first() {
+        Some(addr) => addr,
+        None => Err("this program requires at least one argument")?,
+    };
+    let addr = addr.parse::<SocketAddr>()?;
 
     // Right now Tokio doesn't support a handle to stdin running on the event
     // loop, so we farm out that work to a separate thread. This thread will
     // read data (with blocking I/O) from stdin and then send it to the event
     // loop over a standard futures channel.
     let (stdin_tx, stdin_rx) = mpsc::channel(0);
     thread::spawn(|| read_stdin(stdin_tx));
-    let stdin_rx = stdin_rx.map_err(|_| panic!()); // errors not possible on rx
+    let stdin_rx = stdin_rx.map_err(|_| panic!("errors not possible on rx"));
 
     // Now that we've got our stdin read we either set up our TCP connection or
     // our UDP connection to get a stream of bytes we're going to emit to
     // stdout.
     let stdout = if tcp {
-        tcp::connect(&addr, Box::new(stdin_rx))
+        tcp::connect(&addr, Box::new(stdin_rx))?
     } else {
-        udp::connect(&addr, Box::new(stdin_rx))
+        udp::connect(&addr, Box::new(stdin_rx))?
     };
 
     // And now with our stream of bytes to write to stdout, we execute that in
@@ -77,6 +78,7 @@ fn main() {
             })
             .map_err(|e| println!("error reading stdout; error = {:?}", e))
     });
+    Ok(())
 }
 
 mod codec {
@@ -127,12 +129,13 @@ mod tcp {
     use bytes::BytesMut;
     use codec::Bytes;
 
+    use std::error::Error;
     use std::io;
     use std::net::SocketAddr;
 
     pub fn connect(addr: &SocketAddr,
                    stdin: Box<Stream<Item = Vec<u8>, Error = io::Error> + Send>)
-        -> Box<Stream<Item = BytesMut, Error = io::Error> + Send>
+        -> Result<Box<Stream<Item = BytesMut, Error = io::Error> + Send>, Box<Error>>
     {
         let tcp = TcpStream::connect(addr);
 
@@ -151,22 +154,24 @@ mod tcp {
         // You'll also note that we *spawn* the work to read stdin and write it
         // to the TCP stream. This is done to ensure that happens concurrently
         // with us reading data from the stream.
-        Box::new(tcp.map(move |stream| {
+        let stream = Box::new(tcp.map(move |stream| {
             let (sink, stream) = Bytes.framed(stream).split();
 
             tokio::spawn(stdin.forward(sink).then(|result| {
                 if let Err(e) = result {
-                    panic!("failed to write to socket: {}", e)
+                    println!("failed to write to socket: {}", e)
                 }
                 Ok(())
             }));
 
             stream
-        }).flatten_stream())
+        }).flatten_stream());
+        Ok(stream)
     }
 }
 
 mod udp {
+    use std::error::Error;
     use std::io;
     use std::net::SocketAddr;
 
@@ -179,17 +184,19 @@ mod udp {
 
     pub fn connect(&addr: &SocketAddr,
                    stdin: Box<Stream<Item = Vec<u8>, Error = io::Error> + Send>)
-        -> Box<Stream<Item = BytesMut, Error = io::Error> + Send>
+        -> Result<Box<Stream<Item = BytesMut, Error = io::Error> + Send>, Box<Error>>
     {
         // We'll bind our UDP socket to a local IP/port, but for now we
         // basically let the OS pick both of those.
         let addr_to_bind = if addr.ip().is_ipv4() {
-            "0.0.0.0:0".parse().unwrap()
+            "0.0.0.0:0".parse()?
         } else {
-            "[::]:0".parse().unwrap()
+            "[::]:0".parse()?
+        };
+        let udp = match UdpSocket::bind(&addr_to_bind) {
+            Ok(udp) => udp,
+            Err(_) => Err("failed to bind socket")?,
         };
-        let udp = UdpSocket::bind(&addr_to_bind)
-            .expect("failed to bind socket");
 
         // Like above with TCP we use an instance of `Bytes` codec to transform
         // this UDP socket into a framed sink/stream which operates over
@@ -203,7 +210,7 @@ mod udp {
             (chunk, addr)
         }).forward(sink).then(|result| {
             if let Err(e) = result {
-                panic!("failed to write to socket: {}", e)
+                println!("failed to write to socket: {}", e)
             }
             Ok(())
         });
@@ -218,10 +225,11 @@ mod udp {
             }
         });
 
-        Box::new(future::lazy(|| {
+        let stream = Box::new(future::lazy(|| {
             tokio::spawn(forward_stdin);
             future::ok(receive)
-        }).flatten_stream())
+        }).flatten_stream());
+        Ok(stream)
     }
 }
 

examples/echo-udp.rs

@@ -50,12 +50,12 @@ impl Future for Server {
     }
 }
 
-fn main() {
+fn main() -> Result<(), Box<std::error::Error>> {
     let addr = env::args().nth(1).unwrap_or("127.0.0.1:8080".to_string());
-    let addr = addr.parse::<SocketAddr>().unwrap();
+    let addr = addr.parse::<SocketAddr>()?;
 
-    let socket = UdpSocket::bind(&addr).unwrap();
-    println!("Listening on: {}", socket.local_addr().unwrap());
+    let socket = UdpSocket::bind(&addr)?;
+    println!("Listening on: {}", socket.local_addr()?);
 
     let server = Server {
         socket: socket,
@@ -70,4 +70,5 @@ fn main() {
     //
     // `tokio::run` spawns the task on the Tokio runtime and starts running.
     tokio::run(server.map_err(|e| println!("server error = {:?}", e)));
+    Ok(())
 }

examples/echo.rs

@@ -30,19 +30,19 @@ use tokio::prelude::*;
 use std::env;
 use std::net::SocketAddr;
 
-fn main() {
+fn main() -> Result<(), Box<std::error::Error>> {
     // Allow passing an address to listen on as the first argument of this
     // program, but otherwise we'll just set up our TCP listener on
     // 127.0.0.1:8080 for connections.
     let addr = env::args().nth(1).unwrap_or("127.0.0.1:8080".to_string());
-    let addr = addr.parse::<SocketAddr>().unwrap();
+    let addr = addr.parse::<SocketAddr>()?;
 
     // Next up we create a TCP listener which will listen for incoming
     // connections. This TCP listener is bound to the address we determined
     // above and must be associated with an event loop, so we pass in a handle
     // to our event loop. After the socket's created we inform that we're ready
     // to go and start accepting connections.
-    let socket = TcpListener::bind(&addr).unwrap();
+    let socket = TcpListener::bind(&addr)?;
     println!("Listening on: {}", addr);
 
     // Here we convert the `TcpListener` to a stream of incoming connections
@@ -111,4 +111,5 @@ fn main() {
     // never completes (it just keeps accepting sockets), `tokio::run` blocks
     // forever (until ctrl-c is pressed).
     tokio::run(done);
+    Ok(())
 }

examples/hello_world.rs

@@ -19,8 +19,8 @@ use tokio::io;
 use tokio::net::TcpStream;
 use tokio::prelude::*;
 
-pub fn main() {
-    let addr = "127.0.0.1:6142".parse().unwrap();
+pub fn main() -> Result<(), Box<std::error::Error>> {
+    let addr = "127.0.0.1:6142".parse()?;
 
     // Open a TCP stream to the socket address.
     //
@@ -52,4 +52,6 @@ pub fn main() {
     println!("About to create the stream and write to it...");
     tokio::run(client);
     println!("Stream has been created and written to.");
+
+    Ok(())
 }

examples/manual-runtime.rs

@@ -60,7 +60,7 @@ fn run<F: Future<Item = (), Error = ()>>(f: F) -> Result<(), IoError> {
     Ok(())
 }
 
-fn main() {
+fn main() -> Result<(), Box<std::error::Error>> {
     run(future::lazy(|| {
         // Here comes the application logic. It can spawn further tasks by tokio_current_thread::spawn().
         // It also can use the default reactor and create timeouts.
@@ -82,5 +82,6 @@ fn main() {
         // We can spawn on the default executor, which is also the local one.
         tokio::executor::spawn(deadline);
         Ok(())
-    })).unwrap();
+    }))?;
+    Ok(())
 }

examples/print_each_packet.rs

@@ -65,19 +65,19 @@ use tokio::codec::Decoder;
 use std::env;
 use std::net::SocketAddr;
 
-fn main() {
+fn main() -> Result<(), Box<std::error::Error>> {
     // Allow passing an address to listen on as the first argument of this
     // program, but otherwise we'll just set up our TCP listener on
     // 127.0.0.1:8080 for connections.
     let addr = env::args().nth(1).unwrap_or("127.0.0.1:8080".to_string());
-    let addr = addr.parse::<SocketAddr>().unwrap();
+    let addr = addr.parse::<SocketAddr>()?;
 
     // Next up we create a TCP listener which will listen for incoming
     // connections. This TCP listener is bound to the address we determined
     // above and must be associated with an event loop, so we pass in a handle
     // to our event loop. After the socket's created we inform that we're ready
     // to go and start accepting connections.
-    let socket = TcpListener::bind(&addr).unwrap();
+    let socket = TcpListener::bind(&addr)?;
     println!("Listening on: {}", addr);
 
     // Here we convert the `TcpListener` to a stream of incoming connections
@@ -146,4 +146,5 @@ fn main() {
     // never completes (it just keeps accepting sockets), `tokio::run` blocks
     // forever (until ctrl-c is pressed).
     tokio::run(done);
+    Ok(())
 }

examples/proxy.rs

@@ -33,15 +33,15 @@ use tokio::io::{copy, shutdown};
 use tokio::net::{TcpListener, TcpStream};
 use tokio::prelude::*;
 
-fn main() {
+fn main() -> Result<(), Box<std::error::Error>> {
     let listen_addr = env::args().nth(1).unwrap_or("127.0.0.1:8081".to_string());
-    let listen_addr = listen_addr.parse::<SocketAddr>().unwrap();
+    let listen_addr = listen_addr.parse::<SocketAddr>()?;
 
     let server_addr = env::args().nth(2).unwrap_or("127.0.0.1:8080".to_string());
-    let server_addr = server_addr.parse::<SocketAddr>().unwrap();
+    let server_addr = server_addr.parse::<SocketAddr>()?;
 
     // Create a TCP listener which will listen for incoming connections.
-    let socket = TcpListener::bind(&listen_addr).unwrap();
+    let socket = TcpListener::bind(&listen_addr)?;
     println!("Listening on: {}", listen_addr);
     println!("Proxying to: {}", server_addr);
 
@@ -94,6 +94,7 @@ fn main() {
         });
 
     tokio::run(done);
+    Ok(())
 }
 
 // This is a custom type used to have a custom implementation of the

examples/tinydb.rs

@@ -74,12 +74,12 @@ enum Response {
     Error { msg: String },
 }
 
-fn main() {
+fn main() -> Result<(), Box<std::error::Error>> {
     // Parse the address we're going to run this server on
     // and set up our TCP listener to accept connections.
     let addr = env::args().nth(1).unwrap_or("127.0.0.1:8080".to_string());
-    let addr = addr.parse::<SocketAddr>().unwrap();
-    let listener = TcpListener::bind(&addr).expect("failed to bind");
+    let addr = addr.parse::<SocketAddr>()?;
+    let listener = TcpListener::bind(&addr).map_err(|_| "failed to bind")?;
     println!("Listening on: {}", addr);
 
     // Create the shared state of this server that will be shared amongst all
@@ -156,6 +156,7 @@ fn main() {
         });
 
     tokio::run(done);
+    Ok(())
 }
 
 impl Request {