# error.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/serde_json-1.0.64/src/error.rs`.
Keywords: rust, rustlang, rust-lang

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    //! When serializing or deserializing JSON goes wrong.

    use crate::io;
    use crate::lib::str::FromStr;
    use crate::lib::*;
    use serde::{de, 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::InvalidEscape
                | ErrorCode::InvalidNumber
                | ErrorCode::NumberOutOfRange
                | ErrorCode::InvalidUnicodeCodePoint
                | ErrorCode::ControlCharacterWhileParsingString
                | ErrorCode::KeyMustBeAString
                | 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 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,
    }

    #[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` IO errors.
        /// EOF errors are turned into `UnexpectedEof` IO 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(io::ErrorKind::InvalidData, j),
                    Category::Eof => io::Error::new(io::ErrorKind::UnexpectedEof, j),
                }
            }
        }
    }

    struct ErrorImpl {
        code: ErrorCode,
        line: usize,
        column: usize,
    }

    pub(crate) enum ErrorCode {
        /// Catchall for syntax error messages
        Message(Box<str>),

        /// 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,

        /// 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,

        /// 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 excape.
        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(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::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::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(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 {
            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 {
            if let de::Unexpected::Unit = unexp {
                Error::custom(format_args!("invalid type: null, expected {}", exp))
            } else {
                Error::custom(format_args!("invalid type: {}, expected {}", unexp, exp))
            }
        }
    }

    impl ser::Error for Error {
        #[cold]
        fn custom<T: Display>(msg: T) -> Error {
            make_error(msg.to_string())
        }
    }

    // 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().get(0) {
            None => false,
            Some(&byte) => byte >= b'0' && byte <= b'9',
        }
    }