nanopool 1.1.0

A tiny database connection pooling library for PostgreSQL
Documentation 
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use crate::pool::PoolMessage;

/// Error handling for the pool
#[derive(Debug)]
pub enum PoolError {
    /// A database operation failed
    Database(tokio_postgres::Error),
    /// An I/O operation failed
    Io(std::io::Error),
    /// A message could not be received
    Recv(tokio::sync::oneshot::error::RecvError),
    /// A message could not be sent
    Send(Box<tokio::sync::mpsc::error::SendError<PoolMessage>>),
    /// A TLS error occurred
    Tls(tokio_native_tls::native_tls::Error),
}

/// Convert `PoolError` to a string
impl std::fmt::Display for PoolError {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        match self {
            PoolError::Database(err) => std::fmt::Display::fmt(err, f),
            PoolError::Io(err) => std::fmt::Display::fmt(err, f),
            PoolError::Tls(err) => std::fmt::Display::fmt(err, f),
            PoolError::Recv(err) => std::fmt::Display::fmt(err, f),
            PoolError::Send(err) => std::fmt::Display::fmt(err, f),
        }
    }
}

/// Implement `std::error::Error` for `PoolError`
impl std::error::Error for PoolError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        match self {
            PoolError::Database(err) => Some(err),
            PoolError::Io(err) => Some(err),
            PoolError::Tls(err) => Some(err),
            PoolError::Recv(err) => Some(err),
            PoolError::Send(err) => Some(err),
        }
    }
}

/// Convert `tokio_postgres::Error` to `PoolError`
impl From<tokio_postgres::Error> for PoolError {
    fn from(kind: tokio_postgres::Error) -> Self {
        PoolError::Database(kind)
    }
}

/// Convert `std::io::Error` to `PoolError`
impl From<std::io::Error> for PoolError {
    fn from(kind: std::io::Error) -> Self {
        PoolError::Io(kind)
    }
}

/// Convert `tokio::sync::oneshot::error::RecvError` to `PoolError`
impl From<tokio::sync::oneshot::error::RecvError> for PoolError {
    fn from(kind: tokio::sync::oneshot::error::RecvError) -> Self {
        PoolError::Recv(kind)
    }
}

/// Convert `tokio::sync::mpsc::error::SendError<PoolMessage>` to `PoolError`
impl From<tokio::sync::mpsc::error::SendError<PoolMessage>> for PoolError {
    fn from(kind: tokio::sync::mpsc::error::SendError<PoolMessage>) -> Self {
        PoolError::Send(Box::new(kind))
    }
}

/// Convert `native_tls::Error` to `PoolError`
impl From<tokio_native_tls::native_tls::Error> for PoolError {
    fn from(kind: tokio_native_tls::native_tls::Error) -> Self {
        PoolError::Tls(kind)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    use std::error::Error;

    #[tokio::test]
    async fn test_pool_error_database() {
        let pg_error = tokio_postgres::connect("test.invalid", tokio_postgres::NoTls)
            .await
            .err()
            .unwrap();
        let error = PoolError::from(pg_error);
        let source = error.source().unwrap();
        let message = "invalid connection string: unexpected EOF";
        assert_eq!(error.to_string(), message);
        assert_eq!(source.to_string(), message);
    }

    #[test]
    fn test_pool_error_io() {
        let message = "io error";
        let io_error = std::io::Error::other(message);
        let error = PoolError::from(io_error);
        let source = error.source().unwrap();
        assert_eq!(error.to_string(), message);
        assert_eq!(source.to_string(), message);
    }

    #[tokio::test]
    async fn test_pool_error_recv() {
        let (sender, receiver) = tokio::sync::oneshot::channel::<i32>();
        drop(sender);
        let recv_error = receiver.await.unwrap_err();
        let error = PoolError::from(recv_error);
        let source = error.source().unwrap();
        let message = "channel closed";
        assert_eq!(error.to_string(), message);
        assert_eq!(source.to_string(), message);
    }

    #[tokio::test]
    async fn test_pool_error_send() {
        let (sender, receiver) = tokio::sync::mpsc::channel(1);
        drop(receiver);
        let send_error = sender
            .send(PoolMessage::ReturnClient { client: None })
            .await
            .unwrap_err();
        let error = PoolError::from(send_error);
        let source = error.source().unwrap();
        let message = "channel closed";
        assert_eq!(error.to_string(), message);
        assert_eq!(source.to_string(), message);
    }

    #[test]
    fn test_pool_error_tls() {
        let tls_error = tokio_native_tls::native_tls::Identity::from_pkcs8(&[0xff], &[0xff])
            .err()
            .unwrap();
        let error = PoolError::from(tls_error);
        let source = error.source().unwrap();
        let message = "expected PKCS#8 PEM";
        assert_eq!(error.to_string(), message);
        assert_eq!(source.to_string(), message);
    }
}