Restructure errors

WasNull and BadResponse are gone, and Conversion was added. IoError
covers the BadResponse case and Conversion is a more general version of
WasNull.

src/error.rs

@@ -66,14 +66,14 @@ impl DbErrorNew for DbError {
     fn new_connect<T>(fields: Vec<(u8, String)>) -> result::Result<T, ConnectError> {
         match DbError::new_raw(fields) {
             Ok(err) => Err(ConnectError::DbError(err)),
-            Err(()) => Err(ConnectError::BadResponse),
+            Err(()) => Err(ConnectError::IoError(::bad_response())),
         }
     }
 
     fn new<T>(fields: Vec<(u8, String)>) -> Result<T> {
         match DbError::new_raw(fields) {
             Ok(err) => Err(Error::DbError(err)),
-            Err(()) => Err(Error::BadResponse),
+            Err(()) => Err(Error::IoError(::bad_response())),
         }
     }
 }
@@ -205,11 +205,9 @@ pub enum ConnectError {
     /// The Postgres server does not support SSL encryption.
     NoSslSupport,
     /// There was an error initializing the SSL session
-    SslError(Box<error::Error>),
+    SslError(Box<error::Error+Sync+Send>),
     /// There was an error communicating with the server.
     IoError(io::Error),
-    /// The server sent an unexpected response.
-    BadResponse,
 }
 
 impl fmt::Display for ConnectError {
@@ -235,7 +233,6 @@ impl error::Error for ConnectError {
             ConnectError::NoSslSupport => "The server does not support SSL",
             ConnectError::SslError(_) => "Error initiating SSL session",
             ConnectError::IoError(_) => "Error communicating with server",
-            ConnectError::BadResponse => "The server returned an unexpected response",
         }
     }
 
@@ -296,10 +293,8 @@ pub enum Error {
     WrongType(Type),
     /// An attempt was made to read from a column that does not exist.
     InvalidColumn,
-    /// A value was NULL but converted to a non-nullable Rust type.
+    /// An error converting between Postgres and Rust types.
-    WasNull,
+    Conversion(Box<error::Error+Sync+Send>),
-    /// The server returned an unexpected response.
-    BadResponse,
 }
 
 impl fmt::Display for Error {
@@ -322,8 +317,7 @@ impl error::Error for Error {
             }
             Error::WrongType(_) => "Unexpected type",
             Error::InvalidColumn => "Invalid column",
-            Error::WasNull => "The value was NULL",
+            Error::Conversion(_) => "An error converting between Postgres and Rust types",
-            Error::BadResponse => "The server returned an unexpected response",
         }
     }
 
@@ -331,6 +325,7 @@ impl error::Error for Error {
         match *self {
             Error::DbError(ref err) => Some(err),
             Error::IoError(ref err) => Some(err),
+            Error::Conversion(ref err) => Some(&**err),
             _ => None
         }
     }

src/io/mod.rs

@@ -26,5 +26,6 @@ pub trait NegotiateSsl {
     ///
     /// The host portion of the connection parameters is provided for hostname
     /// verification.
-    fn negotiate_ssl(&self, host: &str, stream: Stream) -> Result<Box<StreamWrapper>, Box<Error>>;
+    fn negotiate_ssl(&self, host: &str, stream: Stream)
+                     -> Result<Box<StreamWrapper>, Box<Error+Sync+Send>>;
 }

src/lib.rs

@@ -402,6 +402,11 @@ pub fn cancel_query<T>(params: T, ssl: &SslMode, data: CancelData)
     Ok(())
 }
 
+fn bad_response() -> std_io::Error {
+    std_io::Error::new(std_io::ErrorKind::InvalidInput,
+                       "the server returned an unexpected response")
+}
+
 /// An enumeration of transaction isolation levels.
 ///
 /// See the [Postgres documentation](http://www.postgresql.org/docs/9.4/static/transaction-iso.html)
@@ -451,7 +456,7 @@ impl IsolationLevel {
         } else if raw.eq_ignore_ascii_case("SERIALIZABLE") {
             Ok(IsolationLevel::Serializable)
         } else {
-            Err(Error::BadResponse)
+            Err(Error::IoError(bad_response()))
         }
     }
 }
@@ -548,7 +553,7 @@ impl InnerConnection {
                 }
                 ReadyForQuery { .. } => break,
                 ErrorResponse { fields } => return DbError::new_connect(fields),
-                _ => return Err(ConnectError::BadResponse),
+                _ => return Err(ConnectError::IoError(bad_response())),
             }
         }
 
@@ -659,13 +664,13 @@ impl InnerConnection {
             | AuthenticationGSS
             | AuthenticationSSPI => return Err(ConnectError::UnsupportedAuthentication),
             ErrorResponse { fields } => return DbError::new_connect(fields),
-            _ => return Err(ConnectError::BadResponse)
+            _ => return Err(ConnectError::IoError(bad_response()))
         }
 
         match try!(self.read_message()) {
             AuthenticationOk => Ok(()),
             ErrorResponse { fields } => return DbError::new_connect(fields),
-            _ => return Err(ConnectError::BadResponse)
+            _ => return Err(ConnectError::IoError(bad_response()))
         }
     }
 
@@ -1469,7 +1474,7 @@ impl<'conn> Statement<'conn> {
             }
             _ => {
                 conn.desynchronized = true;
-                Err(Error::BadResponse)
+                Err(Error::IoError(bad_response()))
             }
         }
     }
@@ -1545,7 +1550,7 @@ impl<'conn> Statement<'conn> {
                 }
                 _ => {
                     conn.desynchronized = true;
-                    return Err(Error::BadResponse);
+                    return Err(Error::IoError(bad_response()));
                 }
             }
         }
@@ -1693,7 +1698,7 @@ fn read_rows(conn: &mut InnerConnection, buf: &mut VecDeque<Vec<Option<Vec<u8>>>
             }
             _ => {
                 conn.desynchronized = true;
-                return Err(Error::BadResponse);
+                return Err(Error::IoError(bad_response()));
             }
         }
     }
@@ -2136,7 +2141,7 @@ impl<'a> CopyInStatement<'a> {
             }
             _ => {
                 conn.desynchronized = true;
-                return Err(Error::BadResponse);
+                return Err(Error::IoError(bad_response()));
             }
         }
 
@@ -2144,7 +2149,7 @@ impl<'a> CopyInStatement<'a> {
             CopyInResponse { .. } => {}
             _ => {
                 conn.desynchronized = true;
-                return Err(Error::BadResponse);
+                return Err(Error::IoError(bad_response()));
             }
         }
 
@@ -2213,7 +2218,7 @@ impl<'a> CopyInStatement<'a> {
             }
             _ => {
                 conn.desynchronized = true;
-                return Err(Error::BadResponse);
+                return Err(Error::IoError(bad_response()));
             }
         };
 

src/macros.rs

@@ -22,6 +22,6 @@ macro_rules! bad_response {
     ($s:expr) => ({
         debug!("Bad response at {}:{}", file!(), line!());
         $s.desynchronized = true;
-        return Err(::Error::BadResponse);
+        return Err(::Error::IoError(::bad_response()));
     })
 }

src/priv_io.rs

@@ -143,7 +143,7 @@ pub fn initialize_stream(params: &ConnectParams, ssl: &SslMode)
     let host = match params.target {
         ConnectTarget::Tcp(ref host) => host,
         #[cfg(feature = "unix_socket")]
-        ConnectTarget::Unix(_) => return Err(ConnectError::BadResponse)
+        ConnectTarget::Unix(_) => return Err(ConnectError::IoError(::bad_response()))
     };
 
     match negotiator.negotiate_ssl(host, socket) {

src/types/mod.rs

@@ -2,6 +2,7 @@
 pub use self::slice::Slice;
 
 use std::collections::HashMap;
+use std::error;
 use std::fmt;
 use std::io::prelude::*;
 use byteorder::{ReadBytesExt, WriteBytesExt, BigEndian};
@@ -514,6 +515,23 @@ impl Other {
     }
 }
 
+/// An error indicating that a `NULL` Postgres value was passed to a `FromSql`
+/// implementation that does not support `NULL` values.
+#[derive(Debug, Clone, Copy)]
+pub struct WasNull;
+
+impl fmt::Display for WasNull {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.write_str(error::Error::description(self))
+    }
+}
+
+impl error::Error for WasNull {
+    fn description(&self) -> &str {
+        "a Postgres value was `NULL`"
+    }
+}
+
 /// A trait for types that can be created from a Postgres value.
 ///
 /// # Types
@@ -566,13 +584,13 @@ pub trait FromSql: Sized {
     /// is compatible with the Postgres `Type`.
     ///
     /// The default implementation calls `FromSql::from_sql` when `raw` is
-    /// `Some` and returns `Err(Error::WasNull)` when `raw` is `None`. It does
+    /// `Some` and returns `Err(Error::Conversion(Box::new(WasNull))` when
-    /// not typically need to be overridden.
+    /// `raw` is `None`. It does not typically need to be overridden.
     fn from_sql_nullable<R: Read>(ty: &Type, raw: Option<&mut R>, ctx: &SessionInfo)
                                   -> Result<Self> {
         match raw {
             Some(raw) => FromSql::from_sql(ty, raw, ctx),
-            None => Err(Error::WasNull),
+            None => Err(Error::Conversion(Box::new(WasNull))),
         }
     }
 
@@ -628,7 +646,7 @@ impl FromSql for String {
     fn from_sql<R: Read>(_: &Type, raw: &mut R, _: &SessionInfo) -> Result<String> {
         let mut buf = vec![];
         try!(raw.read_to_end(&mut buf));
-        String::from_utf8(buf).map_err(|_| Error::BadResponse)
+        String::from_utf8(buf).map_err(|err| Error::Conversion(Box::new(err)))
     }
 
     fn accepts(ty: &Type) -> bool {
@@ -680,7 +698,7 @@ impl FromSql for HashMap<String, Option<String>> {
             try!(util::read_all(raw, &mut key));
             let key = match String::from_utf8(key) {
                 Ok(key) => key,
-                Err(_) => return Err(Error::BadResponse),
+                Err(err) => return Err(Error::Conversion(Box::new(err))),
             };
 
             let val_len = try!(raw.read_i32::<BigEndian>());
@@ -691,7 +709,7 @@ impl FromSql for HashMap<String, Option<String>> {
                 try!(util::read_all(raw, &mut val));
                 match String::from_utf8(val) {
                     Ok(val) => Some(val),
-                    Err(_) => return Err(Error::BadResponse),
+                    Err(err) => return Err(Error::Conversion(Box::new(err))),
                 }
             };
 

src/types/rustc_serialize.rs

@@ -1,4 +1,5 @@
 use serialize::json;
+use std::error;
 use std::io::prelude::*;
 use byteorder::{ReadBytesExt, WriteBytesExt};
 
@@ -10,10 +11,11 @@ impl FromSql for json::Json {
         if let Type::Jsonb = *ty {
             // We only support version 1 of the jsonb binary format
             if try!(raw.read_u8()) != 1 {
-                return Err(Error::BadResponse);
+                let err: Box<error::Error+Sync+Send> = "unsupported JSONB encoding version".into();
+                return Err(Error::Conversion(err));
             }
         }
-        json::Json::from_reader(raw).map_err(|_| Error::BadResponse)
+        json::Json::from_reader(raw).map_err(|err| Error::Conversion(Box::new(err)))
     }
 
     accepts!(Type::Json, Type::Jsonb);

src/types/serde.rs

@@ -1,5 +1,6 @@
 extern crate serde;
 
+use std::error;
 use std::io::prelude::*;
 use byteorder::{ReadBytesExt, WriteBytesExt};
 use self::serde::json::{self, Value};
@@ -12,10 +13,11 @@ impl FromSql for Value {
         if let Type::Jsonb = *ty {
             // We only support version 1 of the jsonb binary format
             if try!(raw.read_u8()) != 1 {
-                return Err(Error::BadResponse);
+                let err: Box<error::Error+Sync+Send> = "unsupported JSONB encoding version".into();
+                return Err(Error::Conversion(err));
             }
         }
-        json::de::from_reader(raw).map_err(|_| Error::BadResponse)
+        json::de::from_reader(raw).map_err(|err| Error::Conversion(Box::new(err)))
     }
 
     accepts!(Type::Json, Type::Jsonb);

src/types/uuid.rs

@@ -4,7 +4,6 @@ use std::io::prelude::*;
 
 use self::uuid::Uuid;
 use types::{FromSql, ToSql, Type, IsNull, SessionInfo};
-use Error;
 use Result;
 use util;
 
@@ -12,10 +11,7 @@ impl FromSql for Uuid {
     fn from_sql<R: Read>(_: &Type, raw: &mut R, _: &SessionInfo) -> Result<Uuid> {
         let mut bytes = [0; 16];
         try!(util::read_all(raw, &mut bytes));
-        match Uuid::from_bytes(&bytes) {
+        Ok(Uuid::from_bytes(&bytes).unwrap())
-            Some(u) => Ok(u),
-            None => Err(Error::BadResponse),
-        }
     }
 
     accepts!(Type::Uuid);

tests/test.rs

@@ -507,7 +507,7 @@ fn test_get_was_null() {
     let result = or_panic!(stmt.query(&[]));
 
     match result.iter().next().unwrap().get_opt::<usize, i32>(0) {
-        Err(Error::WasNull) => {}
+        Err(Error::Conversion(..)) => {}
         res => panic!("unexpected result {:?}", res),
     };
 }