1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
//! Errors, type aliases, and functions related to working with `Result`.

use std::convert::From;
use std::error::Error as StdError;
use std::ffi::NulError;
use std::fmt::{self, Display};

#[derive(Debug)]
#[allow(clippy::enum_variant_names)]
/// Represents all the ways that a query can fail.
///
/// This type is not intended to be exhaustively matched, and new variants may
/// be added in the future without a major version bump.
pub enum Error {
    /// The query contained a nul byte.
    ///
    /// This should never occur in normal usage.
    InvalidCString(NulError),

    /// The database returned an error.
    ///
    /// While Diesel prevents almost all sources of runtime errors at compile
    /// time, it does not attempt to prevent 100% of them. Typically this error
    /// will occur from insert or update statements due to a constraint
    /// violation.
    DatabaseError(
        DatabaseErrorKind,
        Box<dyn DatabaseErrorInformation + Send + Sync>,
    ),

    /// No rows were returned by a query expected to return at least one row.
    ///
    /// This variant is only returned by [`get_result`] and [`first`]. [`load`]
    /// does not treat 0 rows as an error. If you would like to allow either 0
    /// or 1 rows, call [`optional`] on the result.
    ///
    /// [`get_result`]: ../query_dsl/trait.RunQueryDsl.html#method.get_result
    /// [`first`]: ../query_dsl/trait.RunQueryDsl.html#method.first
    /// [`load`]: ../query_dsl/trait.RunQueryDsl.html#method.load
    /// [`optional`]: trait.OptionalExtension.html#tymethod.optional
    NotFound,

    /// The query could not be constructed
    ///
    /// An example of when this error could occur is if you are attempting to
    /// construct an update statement with no changes (e.g. all fields on the
    /// struct are `None`).
    QueryBuilderError(Box<dyn StdError + Send + Sync>),

    /// An error occurred deserializing the data being sent to the database.
    ///
    /// Typically this error means that the stated type of the query is
    /// incorrect. An example of when this error might occur in normal usage is
    /// attempting to deserialize an infinite date into chrono.
    DeserializationError(Box<dyn StdError + Send + Sync>),

    /// An error occurred serializing the data being sent to the database.
    ///
    /// An example of when this error would be returned is if you attempted to
    /// serialize a `chrono::NaiveDate` earlier than the earliest date supported
    /// by PostgreSQL.
    SerializationError(Box<dyn StdError + Send + Sync>),

    /// Roll back the current transaction.
    ///
    /// You can return this variant inside of a transaction when you want to
    /// roll it back, but have no actual error to return. Diesel will never
    /// return this variant unless you gave it to us, and it can be safely
    /// ignored in error handling.
    RollbackTransaction,

    /// Attempted to perform an operation that cannot be done inside a transaction
    /// when a transaction was already open.
    AlreadyInTransaction,

    #[doc(hidden)]
    __Nonexhaustive,
}

#[derive(Debug, Clone, Copy)]
/// The kind of database error that occurred.
///
/// This is not meant to exhaustively cover all possible errors, but is used to
/// identify errors which are commonly recovered from programmatically. This enum
/// is not intended to be exhaustively matched, and new variants may be added in
/// the future without a major version bump.
pub enum DatabaseErrorKind {
    /// A unique constraint was violated.
    UniqueViolation,

    /// A foreign key constraint was violated.
    ForeignKeyViolation,

    /// The query could not be sent to the database due to a protocol violation.
    ///
    /// An example of a case where this would occur is if you attempted to send
    /// a query with more than 65000 bind parameters using PostgreSQL.
    UnableToSendCommand,

    /// A serializable transaction failed to commit due to a read/write
    /// dependency on a concurrent transaction.
    ///
    /// Corresponds to SQLSTATE code 40001
    ///
    /// This error is only detected for PostgreSQL, as we do not yet support
    /// transaction isolation levels for other backends.
    SerializationFailure,

    #[doc(hidden)]
    __Unknown, // Match against _ instead, more variants may be added in the future
}

/// Information about an error that was returned by the database.
pub trait DatabaseErrorInformation {
    /// The primary human-readable error message. Typically one line.
    fn message(&self) -> &str;

    /// An optional secondary error message providing more details about the
    /// problem, if it was provided by the database. Might span multiple lines.
    fn details(&self) -> Option<&str>;

    /// An optional suggestion of what to do about the problem, if one was
    /// provided by the database.
    fn hint(&self) -> Option<&str>;

    /// The name of the table the error was associated with, if the error was
    /// associated with a specific table and the backend supports retrieving
    /// that information.
    ///
    /// Currently this method will return `None` for all backends other than
    /// PostgreSQL.
    fn table_name(&self) -> Option<&str>;

    /// The name of the column the error was associated with, if the error was
    /// associated with a specific column and the backend supports retrieving
    /// that information.
    ///
    /// Currently this method will return `None` for all backends other than
    /// PostgreSQL.
    fn column_name(&self) -> Option<&str>;

    /// The constraint that was violated if this error is a constraint violation
    /// and the backend supports retrieving that information.
    ///
    /// Currently this method will return `None` for all backends other than
    /// PostgreSQL.
    fn constraint_name(&self) -> Option<&str>;
}

impl fmt::Debug for dyn DatabaseErrorInformation + Send + Sync {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Debug::fmt(&self.message(), f)
    }
}

impl DatabaseErrorInformation for String {
    fn message(&self) -> &str {
        self
    }

    fn details(&self) -> Option<&str> {
        None
    }
    fn hint(&self) -> Option<&str> {
        None
    }
    fn table_name(&self) -> Option<&str> {
        None
    }
    fn column_name(&self) -> Option<&str> {
        None
    }
    fn constraint_name(&self) -> Option<&str> {
        None
    }
}

/// Errors which can occur during [`Connection::establish`]
///
/// [`Connection::establish`]: ../connection/trait.Connection.html#tymethod.establish
#[derive(Debug, PartialEq)]
pub enum ConnectionError {
    /// The connection URL contained a `NUL` byte.
    InvalidCString(NulError),
    /// The database returned an error.
    BadConnection(String),
    /// The connection URL could not be parsed.
    InvalidConnectionUrl(String),
    /// Diesel could not configure the database connection.
    ///
    /// Diesel may try to automatically set session specific configuration
    /// values, such as UTF8 encoding, or enabling the `||` operator on MySQL.
    /// This variant is returned if an error occurred executing the query to set
    /// those options. Diesel will never affect global configuration.
    CouldntSetupConfiguration(Error),
    #[doc(hidden)]
    __Nonexhaustive, // Match against _ instead, more variants may be added in the future
}

/// A specialized result type for queries.
///
/// This type is exported by `diesel::prelude`, and is generally used by any
/// code which is interacting with Diesel. This type exists to avoid writing out
/// `diesel::result::Error`, and is otherwise a direct mapping to `Result`.
pub type QueryResult<T> = Result<T, Error>;

/// A specialized result type for establishing connections.
///
/// This type exists to avoid writing out `diesel::result::ConnectionError`, and
/// is otherwise a direct mapping to `Result`.
pub type ConnectionResult<T> = Result<T, ConnectionError>;

/// See the [method documentation](#tymethod.optional).
pub trait OptionalExtension<T> {
    /// Converts a `QueryResult<T>` into a `QueryResult<Option<T>>`.
    ///
    /// By default, Diesel treats 0 rows being returned from a query that is expected to return 1
    /// row as an error (e.g. the return value of [`get_result`] or [`first`]). This method will
    /// handle that error, and give you back an `Option<T>` instead.
    ///
    /// [`get_result`]: ../query_dsl/trait.RunQueryDsl.html#method.get_result
    /// [`first`]: ../query_dsl/trait.RunQueryDsl.html#method.first
    ///
    /// # Example
    ///
    /// ```rust
    /// use diesel::{QueryResult, NotFound, OptionalExtension};
    ///
    /// let result: QueryResult<i32> = Ok(1);
    /// assert_eq!(Ok(Some(1)), result.optional());
    ///
    /// let result: QueryResult<i32> = Err(NotFound);
    /// assert_eq!(Ok(None), result.optional());
    /// ```
    fn optional(self) -> Result<Option<T>, Error>;
}

impl<T> OptionalExtension<T> for QueryResult<T> {
    fn optional(self) -> Result<Option<T>, Error> {
        match self {
            Ok(value) => Ok(Some(value)),
            Err(Error::NotFound) => Ok(None),
            Err(e) => Err(e),
        }
    }
}

impl From<NulError> for ConnectionError {
    fn from(e: NulError) -> Self {
        ConnectionError::InvalidCString(e)
    }
}

impl From<NulError> for Error {
    fn from(e: NulError) -> Self {
        Error::InvalidCString(e)
    }
}

impl Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Error::InvalidCString(ref nul_err) => nul_err.fmt(f),
            Error::DatabaseError(_, ref e) => write!(f, "{}", e.message()),
            Error::NotFound => f.write_str("NotFound"),
            Error::QueryBuilderError(ref e) => e.fmt(f),
            Error::DeserializationError(ref e) => e.fmt(f),
            Error::SerializationError(ref e) => e.fmt(f),
            Error::RollbackTransaction => write!(f, "{}", self.description()),
            Error::AlreadyInTransaction => write!(f, "{}", self.description()),
            Error::__Nonexhaustive => unreachable!(),
        }
    }
}

impl StdError for Error {
    fn description(&self) -> &str {
        match *self {
            Error::InvalidCString(ref nul_err) => nul_err.description(),
            Error::DatabaseError(_, ref e) => e.message(),
            Error::NotFound => "Record not found",
            Error::QueryBuilderError(ref e) => e.description(),
            Error::DeserializationError(ref e) => e.description(),
            Error::SerializationError(ref e) => e.description(),
            Error::RollbackTransaction => "The current transaction was aborted",
            Error::AlreadyInTransaction => {
                "Cannot perform this operation while a transaction is open"
            }
            Error::__Nonexhaustive => unreachable!(),
        }
    }

    fn cause(&self) -> Option<&dyn StdError> {
        match *self {
            Error::InvalidCString(ref e) => Some(e),
            Error::QueryBuilderError(ref e) => Some(&**e),
            Error::DeserializationError(ref e) => Some(&**e),
            Error::SerializationError(ref e) => Some(&**e),
            _ => None,
        }
    }
}

impl Display for ConnectionError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            ConnectionError::InvalidCString(ref nul_err) => nul_err.fmt(f),
            ConnectionError::BadConnection(ref s) => write!(f, "{}", s),
            ConnectionError::InvalidConnectionUrl(ref s) => write!(f, "{}", s),
            ConnectionError::CouldntSetupConfiguration(ref e) => e.fmt(f),
            ConnectionError::__Nonexhaustive => unreachable!(),
        }
    }
}

impl StdError for ConnectionError {
    fn description(&self) -> &str {
        match *self {
            ConnectionError::InvalidCString(ref nul_err) => nul_err.description(),
            ConnectionError::BadConnection(ref s) => s,
            ConnectionError::InvalidConnectionUrl(ref s) => s,
            ConnectionError::CouldntSetupConfiguration(ref e) => e.description(),
            ConnectionError::__Nonexhaustive => unreachable!(),
        }
    }

    fn cause(&self) -> Option<&dyn StdError> {
        match *self {
            ConnectionError::InvalidCString(ref e) => Some(e),
            ConnectionError::CouldntSetupConfiguration(ref e) => Some(e),
            _ => None,
        }
    }
}

impl PartialEq for Error {
    fn eq(&self, other: &Error) -> bool {
        match (self, other) {
            (&Error::InvalidCString(ref a), &Error::InvalidCString(ref b)) => a == b,
            (&Error::DatabaseError(_, ref a), &Error::DatabaseError(_, ref b)) => {
                a.message() == b.message()
            }
            (&Error::NotFound, &Error::NotFound) => true,
            (&Error::RollbackTransaction, &Error::RollbackTransaction) => true,
            (&Error::AlreadyInTransaction, &Error::AlreadyInTransaction) => true,
            _ => false,
        }
    }
}

#[cfg(test)]
#[allow(warnings)]
fn error_impls_send() {
    let err: Error = unimplemented!();
    let x: &Send = &err;
}

pub(crate) fn first_or_not_found<T>(records: QueryResult<Vec<T>>) -> QueryResult<T> {
    records?.into_iter().next().ok_or(Error::NotFound)
}

/// An unexpected `NULL` was encountered during deserialization
#[derive(Debug, Clone, Copy)]
pub struct UnexpectedNullError;

impl fmt::Display for UnexpectedNullError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", self.description())
    }
}

impl StdError for UnexpectedNullError {
    fn description(&self) -> &str {
        "Unexpected null for non-null column"
    }
}