Make tokio_postgres::error::Kind public and add its getter (sfackler#790)

Author: BaptisteRoseau

tokio-postgres/src/error/mod.rs

@@ -336,25 +336,43 @@ pub enum ErrorPosition {
     },
 }
 
+/// The kind of error that occurred.
 #[derive(Debug, PartialEq)]
-enum Kind {
+pub enum Kind {
+    /// An I/O error occurred.
     Io,
+    /// An unexpected message from the server.
     UnexpectedMessage,
+    /// An error occurred during TLS handshake.
     Tls,
+    /// An error occurred while serializing a parameter.
     ToSql(usize),
+    /// An error occurred while deserializing a parameter.
     FromSql(usize),
+    /// An error occurred with a specific column.
     Column(String),
+    /// An error occurred with the parameters.
     Parameters(usize, usize),
+    /// The connection is closed.
     Closed,
+    /// A generic database error occurred.
     Db,
+    /// An error occurred while parsing.
     Parse,
+    /// An error occurred while encoding.
     Encode,
+    /// An authentication error occurred.
     Authentication,
+    /// An error occurred while parsing the configuration.
     ConfigParse,
+    /// An error occurred with the configuration.
     Config,
+    /// An error occurred while counting rows.
     RowCount,
     #[cfg(feature = "runtime")]
+    /// An error occurred while connecting.
     Connect,
+    /// A timeout occurred.
     Timeout,
 }
 
@@ -418,6 +436,11 @@ impl Error {
         self.0.cause
     }
 
+    /// Returns the kind of this error.
+    pub fn kind(&self) -> &Kind {
+        &self.0.kind
+    }
+
     /// Returns the source of this error if it was a `DbError`.
     ///
     /// This is a simple convenience method.

tokio-postgres/src/lib.rs

@@ -125,7 +125,7 @@ pub use crate::connection::Connection;
 pub use crate::copy_in::CopyInSink;
 pub use crate::copy_out::CopyOutStream;
 use crate::error::DbError;
-pub use crate::error::Error;
+pub use crate::error::{Error, Kind};
 pub use crate::generic_client::GenericClient;
 pub use crate::portal::Portal;
 pub use crate::query::RowStream;

tokio-postgres/tests/test/main.rs

@@ -927,6 +927,32 @@ async fn query_opt() {
         .unwrap();
 }
 
+#[tokio::test]
+async fn empty_query_one() {
+    let client = connect("user=postgres").await;
+
+    client
+        .batch_execute(
+            "
+                CREATE TEMPORARY TABLE foo (
+                    name TEXT
+                );
+                INSERT INTO foo (name) VALUES ('alice'), ('bob'), ('carol');
+            ",
+        )
+        .await
+        .unwrap();
+
+    let res = client
+        .query_one("SELECT * FROM foo WHERE name = $1", &[&"not there"])
+        .await;
+    assert!(res.is_err());
+    assert_eq!(
+        res.err().unwrap().kind(),
+        &tokio_postgres::error::Kind::RowCount
+    );
+}
+
 #[tokio::test]
 async fn deferred_constraint() {
     let client = connect("user=postgres").await;