Fix for Document how to deserialize from a prefix of an io::Read with…

…out blocking until EOF #522

src/de.rs

@@ -2193,6 +2193,11 @@ where
 /// as a [`File`], you will want to apply your own buffering because serde_json
 /// will not buffer the input. See [`std::io::BufReader`].
 ///
+/// It is expected that the input stream ends after the deserialized object.
+/// If the stream does not end, such as in the case of a persistent socket connection,
+/// this function will not return. It is possible instead to deserialize from a prefix of an input
+/// stream without looking for EOF by managing your own [`Deserializer`].
+///
 /// Note that counter to intuition, this function is usually slower than
 /// reading a file completely into memory and then applying [`from_str`]
 /// or [`from_slice`] on it. See [issue #160].
@@ -2205,6 +2210,8 @@ where
 ///
 /// # Example
 ///
+/// Reading the contents of a file.
+///
 /// ```edition2018
 /// use serde::Deserialize;
 ///
@@ -2239,6 +2246,36 @@ where
 /// }
 /// ```
 ///
+/// Reading from a persistent socket connection.
+///
+/// ```edition2018
+/// use serde::Deserialize;
+///
+/// use std::error::Error;
+/// use std::net::{TcpListener, TcpStream};
+///
+/// #[derive(Deserialize, Debug)]
+/// struct User {
+///     fingerprint: String,
+///     location: String,
+/// }
+///
+/// fn read_user_from_stream(tcp_stream: TcpStream) -> Result<User, Box<dyn Error>> {
+///     let mut de = serde_json::Deserializer::from_reader(tcp_stream);
+///     let u = User::deserialize(&mut de)?;
+///
+///     Ok(u)
+/// }
+///
+/// fn main() {
+///     let listener = TcpListener::bind("127.0.0.1:4000").unwrap();
+///
+///     for stream in listener.incoming() {
+///         println!("{:#?}", read_user_from_stream(stream.unwrap()));
+///     }
+/// }
+/// ```
+///
 /// # Errors
 ///
 /// This conversion can fail if the structure of the input does not match the