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//! When serializing or deserializing JSON goes wrong.
use crate::io;
use alloc::boxed::Box;
use alloc::string::{String, ToString};
use core::fmt::{self, Debug, Display};
use core::result;
use core::str::FromStr;
use serde::{de, ser};
#[cfg(feature = "std")]
use std::error;
#[cfg(feature = "std")]
use std::io::ErrorKind;
/// 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
/// I/O 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 I/O 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::ExpectedDoubleQuote
| ErrorCode::InvalidEscape
| ErrorCode::InvalidNumber
| ErrorCode::NumberOutOfRange
| ErrorCode::InvalidUnicodeCodePoint
| ErrorCode::ControlCharacterWhileParsingString
| ErrorCode::KeyMustBeAString
| ErrorCode::ExpectedNumericKey
| ErrorCode::FloatKeyMustBeFinite
| ErrorCode::LoneLeadingSurrogateInHexEscape
| ErrorCode::TrailingComma
| 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 I/O 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
}
/// The kind reported by the underlying standard library I/O error, if this
/// error was caused by a failure to read or write bytes on an I/O stream.
///
/// # Example
///
/// ```
/// use serde_json::Value;
/// use std::io::{self, ErrorKind, Read};
/// use std::process;
///
/// struct ReaderThatWillTimeOut<'a>(&'a [u8]);
///
/// impl<'a> Read for ReaderThatWillTimeOut<'a> {
/// fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
/// if self.0.is_empty() {
/// Err(io::Error::new(ErrorKind::TimedOut, "timed out"))
/// } else {
/// self.0.read(buf)
/// }
/// }
/// }
///
/// fn main() {
/// let reader = ReaderThatWillTimeOut(br#" {"k": "#);
///
/// let _: Value = match serde_json::from_reader(reader) {
/// Ok(value) => value,
/// Err(error) => {
/// if error.io_error_kind() == Some(ErrorKind::TimedOut) {
/// // Maybe this application needs to retry certain kinds of errors.
///
/// # return;
/// } else {
/// eprintln!("error: {}", error);
/// process::exit(1);
/// }
/// }
/// };
/// }
/// ```
#[cfg(feature = "std")]
pub fn io_error_kind(&self) -> Option<ErrorKind> {
if let ErrorCode::Io(io_error) = &self.err.code {
Some(io_error.kind())
} else {
None
}
}
}
/// 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 I/O
/// 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,
}
#[cfg(feature = "std")]
#[allow(clippy::fallible_impl_from)]
impl From<Error> for io::Error {
/// Convert a `serde_json::Error` into an `io::Error`.
///
/// JSON syntax and data errors are turned into `InvalidData` I/O errors.
/// EOF errors are turned into `UnexpectedEof` I/O errors.
///
/// ```
/// use std::io;
///
/// enum MyError {
/// Io(io::Error),
/// Json(serde_json::Error),
/// }
///
/// impl From<serde_json::Error> for MyError {
/// fn from(err: serde_json::Error) -> MyError {
/// use serde_json::error::Category;
/// match err.classify() {
/// Category::Io => {
/// MyError::Io(err.into())
/// }
/// Category::Syntax | Category::Data | Category::Eof => {
/// MyError::Json(err)
/// }
/// }
/// }
/// }
/// ```
fn from(j: Error) -> Self {
if let ErrorCode::Io(err) = j.err.code {
err
} else {
match j.classify() {
Category::Io => unreachable!(),
Category::Syntax | Category::Data => io::Error::new(ErrorKind::InvalidData, j),
Category::Eof => io::Error::new(ErrorKind::UnexpectedEof, j),
}
}
}
}
struct ErrorImpl {
code: ErrorCode,
line: usize,
column: usize,
}
pub(crate) enum ErrorCode {
/// Catchall for syntax error messages
Message(Box<str>),
/// Some I/O 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 be a `"`.
ExpectedDoubleQuote,
/// Invalid hex escape code.
InvalidEscape,
/// Invalid number.
InvalidNumber,
/// Number is bigger than the maximum value of its type.
NumberOutOfRange,
/// Invalid unicode code point.
InvalidUnicodeCodePoint,
/// Control character found while parsing a string.
ControlCharacterWhileParsingString,
/// Object key is not a string.
KeyMustBeAString,
/// Contents of key were supposed to be a number.
ExpectedNumericKey,
/// Object key is a non-finite float value.
FloatKeyMustBeFinite,
/// Lone leading surrogate in hex escape.
LoneLeadingSurrogateInHexEscape,
/// JSON has a comma after the last value in an array or map.
TrailingComma,
/// JSON has non-whitespace trailing characters after the value.
TrailingCharacters,
/// Unexpected end of hex escape.
UnexpectedEndOfHexEscape,
/// Encountered nesting of JSON maps and arrays more than 128 layers deep.
RecursionLimitExceeded,
}
impl Error {
#[cold]
pub(crate) fn syntax(code: ErrorCode, line: usize, column: usize) -> Self {
Error {
err: Box::new(ErrorImpl { code, line, column }),
}
}
// Not public API. Should be pub(crate).
//
// Update `eager_json` crate when this function changes.
#[doc(hidden)]
#[cold]
pub fn io(error: io::Error) -> Self {
Error {
err: Box::new(ErrorImpl {
code: ErrorCode::Io(error),
line: 0,
column: 0,
}),
}
}
#[cold]
pub(crate) 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(msg) => f.write_str(msg),
ErrorCode::Io(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::ExpectedDoubleQuote => f.write_str("expected `\"`"),
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::ControlCharacterWhileParsingString => {
f.write_str("control character (\\u0000-\\u001F) found while parsing a string")
}
ErrorCode::KeyMustBeAString => f.write_str("key must be a string"),
ErrorCode::ExpectedNumericKey => {
f.write_str("invalid value: expected key to be a number in quotes")
}
ErrorCode::FloatKeyMustBeFinite => {
f.write_str("float key must be finite (got NaN or +/-inf)")
}
ErrorCode::LoneLeadingSurrogateInHexEscape => {
f.write_str("lone leading surrogate in hex escape")
}
ErrorCode::TrailingComma => f.write_str("trailing comma"),
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 serde::de::StdError for Error {
#[cfg(feature = "std")]
fn source(&self) -> Option<&(dyn error::Error + 'static)> {
match &self.err.code {
ErrorCode::Io(err) => err.source(),
_ => 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 {
write!(
f,
"Error({:?}, line: {}, column: {})",
self.err.code.to_string(),
self.err.line,
self.err.column
)
}
}
impl de::Error for Error {
#[cold]
fn custom<T: Display>(msg: T) -> Error {
make_error(msg.to_string())
}
#[cold]
fn invalid_type(unexp: de::Unexpected, exp: &dyn de::Expected) -> Self {
Error::custom(format_args!(
"invalid type: {}, expected {}",
JsonUnexpected(unexp),
exp,
))
}
#[cold]
fn invalid_value(unexp: de::Unexpected, exp: &dyn de::Expected) -> Self {
Error::custom(format_args!(
"invalid value: {}, expected {}",
JsonUnexpected(unexp),
exp,
))
}
}
impl ser::Error for Error {
#[cold]
fn custom<T: Display>(msg: T) -> Error {
make_error(msg.to_string())
}
}
struct JsonUnexpected<'a>(de::Unexpected<'a>);
impl<'a> Display for JsonUnexpected<'a> {
fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
match self.0 {
de::Unexpected::Unit => formatter.write_str("null"),
de::Unexpected::Float(value) => write!(
formatter,
"floating point `{}`",
ryu::Buffer::new().format(value),
),
unexp => Display::fmt(&unexp, formatter),
}
}
}
// Parse our own error message that looks like "{} at line {} column {}" to work
// around erased-serde round-tripping the error through de::Error::custom.
fn make_error(mut msg: String) -> Error {
let (line, column) = parse_line_col(&mut msg).unwrap_or((0, 0));
Error {
err: Box::new(ErrorImpl {
code: ErrorCode::Message(msg.into_boxed_str()),
line,
column,
}),
}
}
fn parse_line_col(msg: &mut String) -> Option<(usize, usize)> {
let start_of_suffix = match msg.rfind(" at line ") {
Some(index) => index,
None => return None,
};
// Find start and end of line number.
let start_of_line = start_of_suffix + " at line ".len();
let mut end_of_line = start_of_line;
while starts_with_digit(&msg[end_of_line..]) {
end_of_line += 1;
}
if !msg[end_of_line..].starts_with(" column ") {
return None;
}
// Find start and end of column number.
let start_of_column = end_of_line + " column ".len();
let mut end_of_column = start_of_column;
while starts_with_digit(&msg[end_of_column..]) {
end_of_column += 1;
}
if end_of_column < msg.len() {
return None;
}
// Parse numbers.
let line = match usize::from_str(&msg[start_of_line..end_of_line]) {
Ok(line) => line,
Err(_) => return None,
};
let column = match usize::from_str(&msg[start_of_column..end_of_column]) {
Ok(column) => column,
Err(_) => return None,
};
msg.truncate(start_of_suffix);
Some((line, column))
}
fn starts_with_digit(slice: &str) -> bool {
match slice.as_bytes().first() {
None => false,
Some(&byte) => byte >= b'0' && byte <= b'9',
}
}