Permit configuring the notice callback

Right now the behavior is hardcoded to log any received notices at the
info level. Add a `notice_callback` configuration option that permits
installing an arbitrary callback to handle any received notices.

As discussed in sfackler#588.

postgres/src/config.rs

@@ -4,13 +4,16 @@
 
 use crate::connection::Connection;
 use crate::Client;
+use log::info;
 use std::fmt;
 use std::path::Path;
 use std::str::FromStr;
+use std::sync::Arc;
 use std::time::Duration;
 use tokio::runtime;
 #[doc(inline)]
 pub use tokio_postgres::config::{ChannelBinding, Host, SslMode, TargetSessionAttrs};
+use tokio_postgres::error::DbError;
 use tokio_postgres::tls::{MakeTlsConnect, TlsConnect};
 use tokio_postgres::{Error, Socket};
 
@@ -90,6 +93,7 @@ use tokio_postgres::{Error, Socket};
 #[derive(Clone)]
 pub struct Config {
     config: tokio_postgres::Config,
+    notice_callback: Arc<dyn Fn(DbError) + Send + Sync>,
 }
 
 impl fmt::Debug for Config {
@@ -109,9 +113,7 @@ impl Default for Config {
 impl Config {
     /// Creates a new configuration.
     pub fn new() -> Config {
-        Config {
-            config: tokio_postgres::Config::new(),
-        }
+        tokio_postgres::Config::new().into()
     }
 
     /// Sets the user to authenticate with.
@@ -307,6 +309,25 @@ impl Config {
         self.config.get_channel_binding()
     }
 
+    /// Sets the notice callback.
+    ///
+    /// This callback will be invoked with the contents of every
+    /// [`AsyncMessage::Notice`] that is received by the connection. Notices use
+    /// the same structure as errors, but they are not "errors" per-se.
+    ///
+    /// Notices are distinct from notifications, which are instead accessible
+    /// via the [`Notifications`] API.
+    ///
+    /// [`AsyncMessage::Notice`]: tokio_postgres::AsyncMessage::Notice
+    /// [`Notifications`]: crate::Notifications
+    pub fn notice_callback<F>(&mut self, f: F) -> &mut Config
+    where
+        F: Fn(DbError) + Send + Sync + 'static,
+    {
+        self.notice_callback = Arc::new(f);
+        self
+    }
+
     /// Opens a connection to a PostgreSQL database.
     pub fn connect<T>(&self, tls: T) -> Result<Client, Error>
     where
@@ -323,7 +344,7 @@ impl Config {
 
         let (client, connection) = runtime.block_on(self.config.connect(tls))?;
 
-        let connection = Connection::new(runtime, connection);
+        let connection = Connection::new(runtime, connection, self.notice_callback.clone());
         Ok(Client::new(connection, client))
     }
 }
@@ -338,6 +359,11 @@ impl FromStr for Config {
 
 impl From<tokio_postgres::Config> for Config {
     fn from(config: tokio_postgres::Config) -> Config {
-        Config { config }
+        Config {
+            config,
+            notice_callback: Arc::new(|notice| {
+                info!("{}: {}", notice.severity(), notice.message())
+            }),
+        }
     }
 }

postgres/src/connection.rs

@@ -1,24 +1,30 @@
 use crate::{Error, Notification};
 use futures::future;
 use futures::{pin_mut, Stream};
-use log::info;
 use std::collections::VecDeque;
 use std::future::Future;
 use std::ops::{Deref, DerefMut};
 use std::pin::Pin;
+use std::sync::Arc;
 use std::task::{Context, Poll};
 use tokio::io::{AsyncRead, AsyncWrite};
 use tokio::runtime::Runtime;
+use tokio_postgres::error::DbError;
 use tokio_postgres::AsyncMessage;
 
 pub struct Connection {
     runtime: Runtime,
     connection: Pin<Box<dyn Stream<Item = Result<AsyncMessage, Error>> + Send>>,
     notifications: VecDeque<Notification>,
+    notice_callback: Arc<dyn Fn(DbError)>,
 }
 
 impl Connection {
-    pub fn new<S, T>(runtime: Runtime, connection: tokio_postgres::Connection<S, T>) -> Connection
+    pub fn new<S, T>(
+        runtime: Runtime,
+        connection: tokio_postgres::Connection<S, T>,
+        notice_callback: Arc<dyn Fn(DbError)>,
+    ) -> Connection
     where
         S: AsyncRead + AsyncWrite + Unpin + 'static + Send,
         T: AsyncRead + AsyncWrite + Unpin + 'static + Send,
@@ -27,6 +33,7 @@ impl Connection {
             runtime,
             connection: Box::pin(ConnectionStream { connection }),
             notifications: VecDeque::new(),
+            notice_callback,
         }
     }
 
@@ -55,6 +62,7 @@ impl Connection {
     {
         let connection = &mut self.connection;
         let notifications = &mut self.notifications;
+        let notice_callback = &mut self.notice_callback;
         self.runtime.block_on({
             future::poll_fn(|cx| {
                 let done = loop {
@@ -63,7 +71,7 @@ impl Connection {
                             notifications.push_back(notification);
                         }
                         Poll::Ready(Some(Ok(AsyncMessage::Notice(notice)))) => {
-                            info!("{}: {}", notice.severity(), notice.message());
+                            notice_callback(notice)
                         }
                         Poll::Ready(Some(Ok(_))) => {}
                         Poll::Ready(Some(Err(e))) => return Poll::Ready(Err(e)),

postgres/src/test.rs

@@ -1,4 +1,6 @@
 use std::io::{Read, Write};
+use std::str::FromStr;
+use std::sync::mpsc;
 use std::thread;
 use std::time::Duration;
 use tokio_postgres::error::SqlState;
@@ -476,6 +478,22 @@ fn notifications_timeout_iter() {
     assert_eq!(notifications[1].payload(), "world");
 }
 
+#[test]
+fn notice_callback() {
+    let (notice_tx, notice_rx) = mpsc::sync_channel(64);
+    let mut client = Config::from_str("host=localhost port=5433 user=postgres")
+        .unwrap()
+        .notice_callback(move |n| notice_tx.send(n).unwrap())
+        .connect(NoTls)
+        .unwrap();
+
+    client
+        .batch_execute("DO $$BEGIN RAISE NOTICE 'custom'; END$$")
+        .unwrap();
+
+    assert_eq!(notice_rx.recv().unwrap().message(), "custom");
+}
+
 #[test]
 fn explicit_close() {
     let client = Client::connect("host=localhost port=5433 user=postgres", NoTls).unwrap();