From 9b1a45cc6a15f5d2be17531dffc2f50d2b019646 Mon Sep 17 00:00:00 2001
From: Liran Ringel <5730310+liranringel@users.noreply.github.com>
Date: Tue, 20 Nov 2018 18:10:36 +0200
Subject: tests: handle errors properly in examples (#748)

---
 examples/chat-combinator.rs   | 14 +++++++-----
 examples/chat.rs              |  7 +++---
 examples/connect.rs           | 48 +++++++++++++++++++++++-----------------
 examples/echo-udp.rs          |  9 ++++----
 examples/echo.rs              |  7 +++---
 examples/hello_world.rs       |  6 +++--
 examples/manual-runtime.rs    |  5 +++--
 examples/print_each_packet.rs |  7 +++---
 examples/proxy.rs             |  9 ++++----
 examples/tinydb.rs            |  7 +++---
 examples/tinyhttp.rs          | 51 ++++++++++++++++++++++++-------------------
 examples/udp-client.rs        | 27 ++++++++++-------------
 examples/udp-codec.rs         | 11 +++++-----
 13 files changed, 114 insertions(+), 94 deletions(-)

(limited to 'examples')

diff --git a/examples/chat-combinator.rs b/examples/chat-combinator.rs
index 11754183..0572afbd 100644
--- a/examples/chat-combinator.rs
+++ b/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(())
 }
diff --git a/examples/chat.rs b/examples/chat.rs
index bdc742c9..182af7c8 100644
--- a/examples/chat.rs
+++ b/examples/chat.rs
@@ -426,7 +426,7 @@ 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
@@ -434,12 +434,12 @@ pub fn main() {
     // 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(())
 }
diff --git a/examples/connect.rs b/examples/connect.rs
index fa3824c4..93f55533 100644
--- a/examples/connect.rs
+++ b/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") {
@@ -41,10 +41,11 @@ 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
@@ -52,15 +53,15 @@ fn main() {
     // 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)
     }
 }
 
diff --git a/examples/echo-udp.rs b/examples/echo-udp.rs
index 89cc3d16..08a14563 100644
--- a/examples/echo-udp.rs
+++ b/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(())
 }
diff --git a/examples/echo.rs b/examples/echo.rs
index 92d65a90..f33247cb 100644
--- a/examples/echo.rs
+++ b/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(())
 }
diff --git a/examples/hello_world.rs b/examples/hello_world.rs
index c94ec53c..a05a8f22 100644
--- a/examples/hello_world.rs
+++ b/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(())
 }
diff --git a/examples/manual-runtime.rs b/examples/manual-runtime.rs
index 6cbb8cd4..8e3e1299 100644
--- a/examples/manual-runtime.rs
+++ b/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(())
 }
diff --git a/examples/print_each_packet.rs b/examples/print_each_packet.rs
index 644d144c..864d94bd 100644
--- a/examples/print_each_packet.rs
+++ b/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(())
 }
diff --git a/examples/proxy.rs b/examples/proxy.rs
index bed8314a..1df115fd 100644
--- a/examples/proxy.rs
+++ b/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
diff --git a/examples/tinydb.rs b/examples/tinydb.rs
index 134d01b1..702704d3 100644
--- a/examples/tinydb.rs
+++ b/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 {
diff --git a/examples/tinyhttp.rs b/examples/tinyhttp.rs
index 1e4f22bd..7a80d730 100644
--- a/examples/tinyhttp.rs
+++ b/examples/tinyhttp.rs
@@ -34,13 +34,13 @@ use bytes::BytesMut;
 use http::header::HeaderValue;
 use http::{Request, Response, StatusCode};
 
-fn main() {
+fn main() -> Result<(), Box<std::error::Error>> {
     // Parse the arguments, bind the TCP socket we'll be listening to, spin up
     // our worker threads, and start shipping sockets to those worker threads.
     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 listener = TcpListener::bind(&addr).expect("failed to bind");
+    let listener = TcpListener::bind(&addr)?;
     println!("Listening on: {}", addr);
 
     tokio::run({
@@ -51,6 +51,7 @@ fn main() {
                 Ok(())
             })
     });
+    Ok(())
 }
 
 fn process(socket: TcpStream) {
@@ -84,28 +85,32 @@ fn process(socket: TcpStream) {
 fn respond(req: Request<()>)
     -> Box<Future<Item = Response<String>, Error = io::Error> + Send>
 {
-    let mut ret = Response::builder();
-    let body = match req.uri().path() {
-        "/plaintext" => {
-            ret.header("Content-Type", "text/plain");
-            "Hello, World!".to_string()
-        }
-        "/json" => {
-            ret.header("Content-Type", "application/json");
+    let f = future::lazy(move || {
+        let mut response = Response::builder();
+        let body = match req.uri().path() {
+            "/plaintext" => {
+                response.header("Content-Type", "text/plain");
+                "Hello, World!".to_string()
+            }
+            "/json" => {
+                response.header("Content-Type", "application/json");
 
-            #[derive(Serialize)]
-            struct Message {
-                message: &'static str,
+                #[derive(Serialize)]
+                struct Message {
+                    message: &'static str,
+                }
+                serde_json::to_string(&Message { message: "Hello, World!" })?
             }
-            serde_json::to_string(&Message { message: "Hello, World!" })
-                .unwrap()
-        }
-        _ => {
-            ret.status(StatusCode::NOT_FOUND);
-            String::new()
-        }
-    };
-    Box::new(future::ok(ret.body(body).unwrap()))
+            _ => {
+                response.status(StatusCode::NOT_FOUND);
+                String::new()
+            }
+        };
+        let response = response.body(body).map_err(|err| io::Error::new(io::ErrorKind::Other, err))?;
+        Ok(response)
+    });
+
+    Box::new(f)
 }
 
 struct Http;
diff --git a/examples/udp-client.rs b/examples/udp-client.rs
index 3af7c3be..d2d4bc99 100644
--- a/examples/udp-client.rs
+++ b/examples/udp-client.rs
@@ -35,29 +35,27 @@ use std::net::SocketAddr;
 use tokio::net::UdpSocket;
 use tokio::prelude::*;
 
-fn get_stdin_data() -> Vec<u8> {
+fn get_stdin_data() -> Result<Vec<u8>, Box<std::error::Error>> {
     let mut buf = Vec::new();
-    stdin().read_to_end(&mut buf).unwrap();
-    buf
+    stdin().read_to_end(&mut buf)?;
+    Ok(buf)
 }
 
-fn main() {
+fn main() -> Result<(), Box<std::error::Error>> {
     let remote_addr: SocketAddr = env::args()
         .nth(1)
         .unwrap_or("127.0.0.1:8080".into())
-        .parse()
-        .unwrap();
+        .parse()?;
     // We use port 0 to let the operating system allocate an available port for us.
     let local_addr: SocketAddr = if remote_addr.is_ipv4() {
         "0.0.0.0:0"
     } else {
         "[::]:0"
-    }.parse()
-        .unwrap();
-    let socket = UdpSocket::bind(&local_addr).unwrap();
+    }.parse()?;
+    let socket = UdpSocket::bind(&local_addr)?;
     const MAX_DATAGRAM_SIZE: usize = 65_507;
-    let processing = socket
-        .send_dgram(get_stdin_data(), &remote_addr)
+    socket
+        .send_dgram(get_stdin_data()?, &remote_addr)
         .and_then(|(socket, _)| socket.recv_dgram(vec![0u8; MAX_DATAGRAM_SIZE]))
         .map(|(_, data, len, _)| {
             println!(
@@ -66,9 +64,6 @@ fn main() {
                 String::from_utf8_lossy(&data[..len])
             )
         })
-        .wait();
-    match processing {
-        Ok(_) => {}
-        Err(e) => eprintln!("Encountered an error: {}", e),
-    }
+        .wait()?;
+    Ok(())
 }
diff --git a/examples/udp-codec.rs b/examples/udp-codec.rs
index b273a360..837266ac 100644
--- a/examples/udp-codec.rs
+++ b/examples/udp-codec.rs
@@ -19,15 +19,15 @@ use tokio::prelude::*;
 use tokio::net::{UdpSocket, UdpFramed};
 use tokio_codec::BytesCodec;
 
-fn main() {
+fn main() -> Result<(), Box<std::error::Error>> {
     let _ = env_logger::init();
 
-    let addr: SocketAddr = "127.0.0.1:0".parse().unwrap();
+    let addr: SocketAddr = "127.0.0.1:0".parse()?;
 
     // Bind both our sockets and then figure out what ports we got.
-    let a = UdpSocket::bind(&addr).unwrap();
-    let b = UdpSocket::bind(&addr).unwrap();
-    let b_addr = b.local_addr().unwrap();
+    let a = UdpSocket::bind(&addr)?;
+    let b = UdpSocket::bind(&addr)?;
+    let b_addr = b.local_addr()?;
 
     // We're parsing each socket with the `BytesCodec` included in `tokio_io`, and then we
     // `split` each codec into the sink/stream halves.
@@ -61,4 +61,5 @@ fn main() {
             .map(|_| ())
             .map_err(|e| println!("error = {:?}", e))
     });
+    Ok(())
 }
-- 
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