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
//! When serializing or deserializing JSON goes wrong.

use std::error;
use std::fmt::{self, Debug, Display};
use std::io;
use std::result;

use serde::de;
use serde::ser;

/// This type represents all possible errors that can occur when serializing or
/// deserializing JSON data.
pub struct Error {
    /// This `Box` allows us to keep the size of `Error` as small as possible. A
    /// larger `Error` type was substantially slower due to all the functions
    /// that pass around `Result<T, Error>`.
    err: Box<ErrorImpl>,
}

/// Alias for a `Result` with the error type `serde_json::Error`.
pub type Result<T> = result::Result<T, Error>;

impl Error {
    /// One-based line number at which the error was detected.
    ///
    /// Characters in the first line of the input (before the first newline
    /// character) are in line 1.
    pub fn line(&self) -> usize {
        self.err.line
    }

    /// One-based column number at which the error was detected.
    ///
    /// The first character in the input and any characters immediately
    /// following a newline character are in column 1.
    ///
    /// Note that errors may occur in column 0, for example if a read from an IO
    /// stream fails immediately following a previously read newline character.
    pub fn column(&self) -> usize {
        self.err.column
    }

    /// Categorizes the cause of this error.
    ///
    /// - `Category::Io` - failure to read or write bytes on an IO stream
    /// - `Category::Syntax` - input that is not syntactically valid JSON
    /// - `Category::Data` - input data that is semantically incorrect
    /// - `Category::Eof` - unexpected end of the input data
    pub fn classify(&self) -> Category {
        match self.err.code {
            ErrorCode::Message(_) => Category::Data,
            ErrorCode::Io(_) => Category::Io,
            ErrorCode::EofWhileParsingList |
            ErrorCode::EofWhileParsingObject |
            ErrorCode::EofWhileParsingString |
            ErrorCode::EofWhileParsingValue => Category::Eof,
            ErrorCode::ExpectedColon |
            ErrorCode::ExpectedListCommaOrEnd |
            ErrorCode::ExpectedObjectCommaOrEnd |
            ErrorCode::ExpectedSomeIdent |
            ErrorCode::ExpectedSomeValue |
            ErrorCode::ExpectedSomeString |
            ErrorCode::InvalidEscape |
            ErrorCode::InvalidNumber |
            ErrorCode::NumberOutOfRange |
            ErrorCode::InvalidUnicodeCodePoint |
            ErrorCode::KeyMustBeAString |
            ErrorCode::LoneLeadingSurrogateInHexEscape |
            ErrorCode::TrailingCharacters |
            ErrorCode::UnexpectedEndOfHexEscape |
            ErrorCode::RecursionLimitExceeded => Category::Syntax,
        }
    }

    /// Returns true if this error was caused by a failure to read or write
    /// bytes on an IO stream.
    pub fn is_io(&self) -> bool {
        self.classify() == Category::Io
    }

    /// Returns true if this error was caused by input that was not
    /// syntactically valid JSON.
    pub fn is_syntax(&self) -> bool {
        self.classify() == Category::Syntax
    }

    /// Returns true if this error was caused by input data that was
    /// semantically incorrect.
    ///
    /// For example, JSON containing a number is semantically incorrect when the
    /// type being deserialized into holds a String.
    pub fn is_data(&self) -> bool {
        self.classify() == Category::Data
    }

    /// Returns true if this error was caused by prematurely reaching the end of
    /// the input data.
    ///
    /// Callers that process streaming input may be interested in retrying the
    /// deserialization once more data is available.
    pub fn is_eof(&self) -> bool {
        self.classify() == Category::Eof
    }
}

/// Categorizes the cause of a `serde_json::Error`.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub enum Category {
    /// The error was caused by a failure to read or write bytes on an IO
    /// stream.
    Io,

    /// The error was caused by input that was not syntactically valid JSON.
    Syntax,

    /// The error was caused by input data that was semantically incorrect.
    ///
    /// For example, JSON containing a number is semantically incorrect when the
    /// type being deserialized into holds a String.
    Data,

    /// The error was caused by prematurely reaching the end of the input data.
    ///
    /// Callers that process streaming input may be interested in retrying the
    /// deserialization once more data is available.
    Eof,
}

#[derive(Debug)]
struct ErrorImpl {
    code: ErrorCode,
    line: usize,
    column: usize,
}

// Not public API. Should be pub(crate).
#[doc(hidden)]
#[derive(Debug)]
pub enum ErrorCode {
    /// Catchall for syntax error messages
    Message(String),

    /// Some IO error occurred while serializing or deserializing.
    Io(io::Error),

    /// EOF while parsing a list.
    EofWhileParsingList,

    /// EOF while parsing an object.
    EofWhileParsingObject,

    /// EOF while parsing a string.
    EofWhileParsingString,

    /// EOF while parsing a JSON value.
    EofWhileParsingValue,

    /// Expected this character to be a `':'`.
    ExpectedColon,

    /// Expected this character to be either a `','` or a `]`.
    ExpectedListCommaOrEnd,

    /// Expected this character to be either a `','` or a `}`.
    ExpectedObjectCommaOrEnd,

    /// Expected to parse either a `true`, `false`, or a `null`.
    ExpectedSomeIdent,

    /// Expected this character to start a JSON value.
    ExpectedSomeValue,

    /// Expected this character to start a JSON string.
    ExpectedSomeString,

    /// Invalid hex escape code.
    InvalidEscape,

    /// Invalid number.
    InvalidNumber,

    /// Number is bigger than the maximum value of its type.
    NumberOutOfRange,

    /// Invalid unicode code point.
    InvalidUnicodeCodePoint,

    /// Object key is not a string.
    KeyMustBeAString,

    /// Lone leading surrogate in hex escape.
    LoneLeadingSurrogateInHexEscape,

    /// JSON has non-whitespace trailing characters after the value.
    TrailingCharacters,

    /// Unexpected end of hex excape.
    UnexpectedEndOfHexEscape,

    /// Encountered nesting of JSON maps and arrays more than 128 layers deep.
    RecursionLimitExceeded,
}

impl Error {
    // Not public API. Should be pub(crate).
    #[doc(hidden)]
    pub fn syntax(code: ErrorCode, line: usize, column: usize) -> Self {
        Error {
            err: Box::new(ErrorImpl { code: code, line: line, column: column }),
        }
    }

    // Not public API. Should be pub(crate).
    #[doc(hidden)]
    pub fn fix_position<F>(self, f: F) -> Self
        where F: FnOnce(ErrorCode) -> Error
    {
        if self.err.line == 0 {
            f(self.err.code)
        } else {
            self
        }
    }
}

impl Display for ErrorCode {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            ErrorCode::Message(ref msg) => f.write_str(msg),
            ErrorCode::Io(ref err) => Display::fmt(err, f),
            ErrorCode::EofWhileParsingList => {
                f.write_str("EOF while parsing a list")
            }
            ErrorCode::EofWhileParsingObject => {
                f.write_str("EOF while parsing an object")
            }
            ErrorCode::EofWhileParsingString => {
                f.write_str("EOF while parsing a string")
            }
            ErrorCode::EofWhileParsingValue => {
                f.write_str("EOF while parsing a value")
            }
            ErrorCode::ExpectedColon => {
                f.write_str("expected `:`")
            }
            ErrorCode::ExpectedListCommaOrEnd => {
                f.write_str("expected `,` or `]`")
            }
            ErrorCode::ExpectedObjectCommaOrEnd => {
                f.write_str("expected `,` or `}`")
            }
            ErrorCode::ExpectedSomeIdent => {
                f.write_str("expected ident")
            }
            ErrorCode::ExpectedSomeValue => {
                f.write_str("expected value")
            }
            ErrorCode::ExpectedSomeString => {
                f.write_str("expected string")
            }
            ErrorCode::InvalidEscape => {
                f.write_str("invalid escape")
            }
            ErrorCode::InvalidNumber => {
                f.write_str("invalid number")
            }
            ErrorCode::NumberOutOfRange => {
                f.write_str("number out of range")
            }
            ErrorCode::InvalidUnicodeCodePoint => {
                f.write_str("invalid unicode code point")
            }
            ErrorCode::KeyMustBeAString => {
                f.write_str("key must be a string")
            }
            ErrorCode::LoneLeadingSurrogateInHexEscape => {
                f.write_str("lone leading surrogate in hex escape")
            }
            ErrorCode::TrailingCharacters => {
                f.write_str("trailing characters")
            }
            ErrorCode::UnexpectedEndOfHexEscape => {
                f.write_str("unexpected end of hex escape")
            }
            ErrorCode::RecursionLimitExceeded => {
                f.write_str("recursion limit exceeded")
            }
        }
    }
}

impl error::Error for Error {
    fn description(&self) -> &str {
        match self.err.code {
            ErrorCode::Io(ref err) => error::Error::description(err),
            _ => {
                // If you want a better message, use Display::fmt or to_string().
                "JSON error"
            }
        }
    }

    fn cause(&self) -> Option<&error::Error> {
        match self.err.code {
            ErrorCode::Io(ref err) => Some(err),
            _ => None,
        }
    }
}

impl Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        Display::fmt(&*self.err, f)
    }
}

impl Display for ErrorImpl {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        if self.line == 0 {
            Display::fmt(&self.code, f)
        } else {
            write!(f, "{} at line {} column {}", self.code, self.line, self.column)
        }
    }
}

// Remove two layers of verbosity from the debug representation. Humans often
// end up seeing this representation because it is what unwrap() shows.
impl Debug for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        Debug::fmt(&*self.err, f)
    }
}

impl From<ErrorImpl> for Error {
    fn from(error: ErrorImpl)  -> Error {
        Error {
            err: Box::new(error),
        }
    }
}

impl From<io::Error> for Error {
    fn from(error: io::Error) -> Error {
        Error {
            err: Box::new(ErrorImpl { code: ErrorCode::Io(error), line: 0, column: 0 }),
        }
    }
}

impl From<de::value::Error> for Error {
    fn from(error: de::value::Error) -> Error {
        Error {
            err: Box::new(ErrorImpl { code: ErrorCode::Message(error.to_string()), line: 0, column: 0 }),
        }
    }
}

impl de::Error for Error {
    fn custom<T: Display>(msg: T) -> Error {
        Error {
            err: Box::new(ErrorImpl { code: ErrorCode::Message(msg.to_string()), line: 0, column: 0 }),
        }
    }
}

impl ser::Error for Error {
    fn custom<T: Display>(msg: T) -> Error {
        Error {
            err: Box::new(ErrorImpl { code: ErrorCode::Message(msg.to_string()), line: 0, column: 0 }),
        }
    }
}