Struct Error

pub struct Error { /* private fields */ }

This type represents all possible errors that can occur when serializing or deserializing JSON data.

Implementations

impl Error

pub fn line(&self) -> usize

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 column(&self) -> usize

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 classify(&self) -> Category

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 is_io(&self) -> bool

Returns true if this error was caused by a failure to read or write bytes on an I/O stream.

pub fn is_syntax(&self) -> bool

Returns true if this error was caused by input that was not syntactically valid JSON.

pub fn is_data(&self) -> bool

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_eof(&self) -> bool

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 io_error_kind(&self) -> Option<ErrorKind>

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.

            } else {
                eprintln!("error: {}", error);
                process::exit(1);
            }
        }
    };
}

Trait Implementations

impl Debug for Error

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for Error

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Error for Error

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0: use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0: replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl Error for Error

fn custom<T: Display>(msg: T) -> Error

Raised when there is general error when deserializing a type.

fn invalid_type(unexp: Unexpected<'_>, exp: &dyn Expected) -> Self

Raised when a Deserialize receives a type different from what it was expecting.

fn invalid_value(unexp: Unexpected<'_>, exp: &dyn Expected) -> Self

Raised when a Deserialize receives a value of the right type but that is wrong for some other reason.

fn invalid_length(len: usize, exp: &dyn Expected) -> Self

Raised when deserializing a sequence or map and the input data contains too many or too few elements.

fn unknown_variant(variant: &str, expected: &'static [&'static str]) -> Self

Raised when a Deserialize enum type received a variant with an unrecognized name.

fn unknown_field(field: &str, expected: &'static [&'static str]) -> Self

Raised when a Deserialize struct type received a field with an unrecognized name.

fn missing_field(field: &'static str) -> Self

Raised when a Deserialize struct type expected to receive a required field with a particular name but that field was not present in the input.

fn duplicate_field(field: &'static str) -> Self

Raised when a Deserialize struct type received more than one of the same field.

impl Error for Error

fn custom<T: Display>(msg: T) -> Error

Used when a Serialize implementation encounters any error while serializing a type.

impl From<Error> for Error

fn from(j: Error) -> Self

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)
            }
        }
    }
}

impl<'de> IntoDeserializer<'de, Error> for &'de Map<String, Value>

type Deserializer = &'de Map<String, Value>

The type of the deserializer being converted into.

fn into_deserializer(self) -> Self::Deserializer

Convert this value into a deserializer.

impl<'de> IntoDeserializer<'de, Error> for &'de Value

type Deserializer = &'de Value

The type of the deserializer being converted into.

fn into_deserializer(self) -> Self::Deserializer

Convert this value into a deserializer.

impl<'de> IntoDeserializer<'de, Error> for Map<String, Value>

type Deserializer = Map<String, Value>

The type of the deserializer being converted into.

fn into_deserializer(self) -> Self::Deserializer

Convert this value into a deserializer.

impl<'de> IntoDeserializer<'de, Error> for Value

type Deserializer = Value

The type of the deserializer being converted into.

fn into_deserializer(self) -> Self::Deserializer

Convert this value into a deserializer.