//! Error management
//!
//! Parsers are generic over their error type, requiring that it implements
//! the `error::ParseError` trait.
use crate::internal::Parser;
use crate::lib::std::fmt;
/// This trait must be implemented by the error type of a nom parser.
///
/// There are already implementations of it for `(Input, ErrorKind)`
/// and `VerboseError`.
///
/// It provides methods to create an error from some combinators,
/// and combine existing errors in combinators like `alt`.
pub trait ParseError: Sized {
/// Creates an error from the input position and an [ErrorKind]
fn from_error_kind(input: I, kind: ErrorKind) -> Self;
/// Combines an existing error with a new one created from the input
/// position and an [ErrorKind]. This is useful when backtracking
/// through a parse tree, accumulating error context on the way
fn append(input: I, kind: ErrorKind, other: Self) -> Self;
/// Creates an error from an input position and an expected character
fn from_char(input: I, _: char) -> Self {
Self::from_error_kind(input, ErrorKind::Char)
}
/// Combines two existing errors. This function is used to compare errors
/// generated in various branches of `alt`.
fn or(self, other: Self) -> Self {
other
}
}
/// This trait is required by the `context` combinator to add a static string
/// to an existing error
pub trait ContextError: Sized {
/// Creates a new error from an input position, a static string and an existing error.
/// This is used mainly in the [context] combinator, to add user friendly information
/// to errors when backtracking through a parse tree
fn add_context(_input: I, _ctx: &'static str, other: Self) -> Self {
other
}
}
/// This trait is required by the `map_res` combinator to integrate
/// error types from external functions, like [std::str::FromStr]
pub trait FromExternalError {
/// Creates a new error from an input position, an [ErrorKind] indicating the
/// wrapping parser, and an external error
fn from_external_error(input: I, kind: ErrorKind, e: E) -> Self;
}
/// default error type, only contains the error' location and code
#[derive(Debug, PartialEq)]
pub struct Error {
/// position of the error in the input data
pub input: I,
/// nom error code
pub code: ErrorKind,
}
impl Error {
/// creates a new basic error
pub fn new(input: I, code: ErrorKind) -> Error {
Error { input, code }
}
}
impl ParseError for Error {
fn from_error_kind(input: I, kind: ErrorKind) -> Self {
Error { input, code: kind }
}
fn append(_: I, _: ErrorKind, other: Self) -> Self {
other
}
}
impl ContextError for Error {}
impl FromExternalError for Error {
/// Create a new error from an input position and an external error
fn from_external_error(input: I, kind: ErrorKind, _e: E) -> Self {
Error { input, code: kind }
}
}
/// The Display implementation allows the std::error::Error implementation
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "error {:?} at: {}", self.code, self.input)
}
}
#[cfg(feature = "std")]
impl std::error::Error for Error {}
// for backward compatibility, keep those trait implementations
// for the previously used error type
impl ParseError for (I, ErrorKind) {
fn from_error_kind(input: I, kind: ErrorKind) -> Self {
(input, kind)
}
fn append(_: I, _: ErrorKind, other: Self) -> Self {
other
}
}
impl ContextError for (I, ErrorKind) {}
impl FromExternalError for (I, ErrorKind) {
fn from_external_error(input: I, kind: ErrorKind, _e: E) -> Self {
(input, kind)
}
}
impl ParseError for () {
fn from_error_kind(_: I, _: ErrorKind) -> Self {}
fn append(_: I, _: ErrorKind, _: Self) -> Self {}
}
impl ContextError for () {}
impl FromExternalError for () {
fn from_external_error(_input: I, _kind: ErrorKind, _e: E) -> Self {}
}
/// Creates an error from the input position and an [ErrorKind]
pub fn make_error>(input: I, kind: ErrorKind) -> E {
E::from_error_kind(input, kind)
}
/// Combines an existing error with a new one created from the input
/// position and an [ErrorKind]. This is useful when backtracking
/// through a parse tree, accumulating error context on the way
pub fn append_error>(input: I, kind: ErrorKind, other: E) -> E {
E::append(input, kind, other)
}
/// This error type accumulates errors and their position when backtracking
/// through a parse tree. With some post processing (cf `examples/json.rs`),
/// it can be used to display user friendly error messages
#[cfg(feature = "alloc")]
#[cfg_attr(feature = "docsrs", doc(cfg(feature = "alloc")))]
#[derive(Clone, Debug, PartialEq)]
pub struct VerboseError {
/// List of errors accumulated by `VerboseError`, containing the affected
/// part of input data, and some context
pub errors: crate::lib::std::vec::Vec<(I, VerboseErrorKind)>,
}
#[cfg(feature = "alloc")]
#[cfg_attr(feature = "docsrs", doc(cfg(feature = "alloc")))]
#[derive(Clone, Debug, PartialEq)]
/// Error context for `VerboseError`
pub enum VerboseErrorKind {
/// Static string added by the `context` function
Context(&'static str),
/// Indicates which character was expected by the `char` function
Char(char),
/// Error kind given by various nom parsers
Nom(ErrorKind),
}
#[cfg(feature = "alloc")]
#[cfg_attr(feature = "docsrs", doc(cfg(feature = "alloc")))]
impl ParseError for VerboseError {
fn from_error_kind(input: I, kind: ErrorKind) -> Self {
VerboseError {
errors: vec![(input, VerboseErrorKind::Nom(kind))],
}
}
fn append(input: I, kind: ErrorKind, mut other: Self) -> Self {
other.errors.push((input, VerboseErrorKind::Nom(kind)));
other
}
fn from_char(input: I, c: char) -> Self {
VerboseError {
errors: vec![(input, VerboseErrorKind::Char(c))],
}
}
}
#[cfg(feature = "alloc")]
#[cfg_attr(feature = "docsrs", doc(cfg(feature = "alloc")))]
impl ContextError for VerboseError {
fn add_context(input: I, ctx: &'static str, mut other: Self) -> Self {
other.errors.push((input, VerboseErrorKind::Context(ctx)));
other
}
}
#[cfg(feature = "alloc")]
#[cfg_attr(feature = "docsrs", doc(cfg(feature = "alloc")))]
impl FromExternalError for VerboseError {
/// Create a new error from an input position and an external error
fn from_external_error(input: I, kind: ErrorKind, _e: E) -> Self {
Self::from_error_kind(input, kind)
}
}
#[cfg(feature = "alloc")]
impl fmt::Display for VerboseError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
writeln!(f, "Parse error:")?;
for (input, error) in &self.errors {
match error {
VerboseErrorKind::Nom(e) => writeln!(f, "{:?} at: {}", e, input)?,
VerboseErrorKind::Char(c) => writeln!(f, "expected '{}' at: {}", c, input)?,
VerboseErrorKind::Context(s) => writeln!(f, "in section '{}', at: {}", s, input)?,
}
}
Ok(())
}
}
#[cfg(feature = "std")]
impl std::error::Error for VerboseError {}
use crate::internal::{Err, IResult};
/// Create a new error from an input position, a static string and an existing error.
/// This is used mainly in the [context] combinator, to add user friendly information
/// to errors when backtracking through a parse tree
pub fn context, F, O>(
context: &'static str,
mut f: F,
) -> impl FnMut(I) -> IResult
where
F: Parser,
{
move |i: I| match f.parse(i.clone()) {
Ok(o) => Ok(o),
Err(Err::Incomplete(i)) => Err(Err::Incomplete(i)),
Err(Err::Error(e)) => Err(Err::Error(E::add_context(i, context, e))),
Err(Err::Failure(e)) => Err(Err::Failure(E::add_context(i, context, e))),
}
}
/// Transforms a `VerboseError` into a trace with input position information
#[cfg(feature = "alloc")]
#[cfg_attr(feature = "docsrs", doc(cfg(feature = "alloc")))]
pub fn convert_error>(
input: I,
e: VerboseError,
) -> crate::lib::std::string::String {
use crate::lib::std::fmt::Write;
use crate::traits::Offset;
let mut result = crate::lib::std::string::String::new();
for (i, (substring, kind)) in e.errors.iter().enumerate() {
let offset = input.offset(substring);
if input.is_empty() {
match kind {
VerboseErrorKind::Char(c) => {
write!(&mut result, "{}: expected '{}', got empty input\n\n", i, c)
}
VerboseErrorKind::Context(s) => write!(&mut result, "{}: in {}, got empty input\n\n", i, s),
VerboseErrorKind::Nom(e) => write!(&mut result, "{}: in {:?}, got empty input\n\n", i, e),
}
} else {
let prefix = &input.as_bytes()[..offset];
// Count the number of newlines in the first `offset` bytes of input
let line_number = prefix.iter().filter(|&&b| b == b'\n').count() + 1;
// Find the line that includes the subslice:
// Find the *last* newline before the substring starts
let line_begin = prefix
.iter()
.rev()
.position(|&b| b == b'\n')
.map(|pos| offset - pos)
.unwrap_or(0);
// Find the full line after that newline
let line = input[line_begin..]
.lines()
.next()
.unwrap_or(&input[line_begin..])
.trim_end();
// The (1-indexed) column number is the offset of our substring into that line
let column_number = line.offset(substring) + 1;
match kind {
VerboseErrorKind::Char(c) => {
if let Some(actual) = substring.chars().next() {
write!(
&mut result,
"{i}: at line {line_number}:\n\
{line}\n\
{caret:>column$}\n\
expected '{expected}', found {actual}\n\n",
i = i,
line_number = line_number,
line = line,
caret = '^',
column = column_number,
expected = c,
actual = actual,
)
} else {
write!(
&mut result,
"{i}: at line {line_number}:\n\
{line}\n\
{caret:>column$}\n\
expected '{expected}', got end of input\n\n",
i = i,
line_number = line_number,
line = line,
caret = '^',
column = column_number,
expected = c,
)
}
}
VerboseErrorKind::Context(s) => write!(
&mut result,
"{i}: at line {line_number}, in {context}:\n\
{line}\n\
{caret:>column$}\n\n",
i = i,
line_number = line_number,
context = s,
line = line,
caret = '^',
column = column_number,
),
VerboseErrorKind::Nom(e) => write!(
&mut result,
"{i}: at line {line_number}, in {nom_err:?}:\n\
{line}\n\
{caret:>column$}\n\n",
i = i,
line_number = line_number,
nom_err = e,
line = line,
caret = '^',
column = column_number,
),
}
}
// Because `write!` to a `String` is infallible, this `unwrap` is fine.
.unwrap();
}
result
}
/// Indicates which parser returned an error
#[rustfmt::skip]
#[derive(Debug,PartialEq,Eq,Hash,Clone,Copy)]
#[allow(deprecated,missing_docs)]
pub enum ErrorKind {
Tag,
MapRes,
MapOpt,
Alt,
IsNot,
IsA,
SeparatedList,
SeparatedNonEmptyList,
Many0,
Many1,
ManyTill,
Count,
TakeUntil,
LengthValue,
TagClosure,
Alpha,
Digit,
HexDigit,
OctDigit,
AlphaNumeric,
Space,
MultiSpace,
LengthValueFn,
Eof,
Switch,
TagBits,
OneOf,
NoneOf,
Char,
CrLf,
RegexpMatch,
RegexpMatches,
RegexpFind,
RegexpCapture,
RegexpCaptures,
TakeWhile1,
Complete,
Fix,
Escaped,
EscapedTransform,
NonEmpty,
ManyMN,
Not,
Permutation,
Verify,
TakeTill1,
TakeWhileMN,
TooLarge,
Many0Count,
Many1Count,
Float,
Satisfy,
Fail,
}
#[rustfmt::skip]
#[allow(deprecated)]
/// Converts an ErrorKind to a number
pub fn error_to_u32(e: &ErrorKind) -> u32 {
match *e {
ErrorKind::Tag => 1,
ErrorKind::MapRes => 2,
ErrorKind::MapOpt => 3,
ErrorKind::Alt => 4,
ErrorKind::IsNot => 5,
ErrorKind::IsA => 6,
ErrorKind::SeparatedList => 7,
ErrorKind::SeparatedNonEmptyList => 8,
ErrorKind::Many1 => 9,
ErrorKind::Count => 10,
ErrorKind::TakeUntil => 12,
ErrorKind::LengthValue => 15,
ErrorKind::TagClosure => 16,
ErrorKind::Alpha => 17,
ErrorKind::Digit => 18,
ErrorKind::AlphaNumeric => 19,
ErrorKind::Space => 20,
ErrorKind::MultiSpace => 21,
ErrorKind::LengthValueFn => 22,
ErrorKind::Eof => 23,
ErrorKind::Switch => 27,
ErrorKind::TagBits => 28,
ErrorKind::OneOf => 29,
ErrorKind::NoneOf => 30,
ErrorKind::Char => 40,
ErrorKind::CrLf => 41,
ErrorKind::RegexpMatch => 42,
ErrorKind::RegexpMatches => 43,
ErrorKind::RegexpFind => 44,
ErrorKind::RegexpCapture => 45,
ErrorKind::RegexpCaptures => 46,
ErrorKind::TakeWhile1 => 47,
ErrorKind::Complete => 48,
ErrorKind::Fix => 49,
ErrorKind::Escaped => 50,
ErrorKind::EscapedTransform => 51,
ErrorKind::NonEmpty => 56,
ErrorKind::ManyMN => 57,
ErrorKind::HexDigit => 59,
ErrorKind::OctDigit => 61,
ErrorKind::Many0 => 62,
ErrorKind::Not => 63,
ErrorKind::Permutation => 64,
ErrorKind::ManyTill => 65,
ErrorKind::Verify => 66,
ErrorKind::TakeTill1 => 67,
ErrorKind::TakeWhileMN => 69,
ErrorKind::TooLarge => 70,
ErrorKind::Many0Count => 71,
ErrorKind::Many1Count => 72,
ErrorKind::Float => 73,
ErrorKind::Satisfy => 74,
ErrorKind::Fail => 75,
}
}
impl ErrorKind {
#[rustfmt::skip]
#[allow(deprecated)]
/// Converts an ErrorKind to a text description
pub fn description(&self) -> &str {
match *self {
ErrorKind::Tag => "Tag",
ErrorKind::MapRes => "Map on Result",
ErrorKind::MapOpt => "Map on Option",
ErrorKind::Alt => "Alternative",
ErrorKind::IsNot => "IsNot",
ErrorKind::IsA => "IsA",
ErrorKind::SeparatedList => "Separated list",
ErrorKind::SeparatedNonEmptyList => "Separated non empty list",
ErrorKind::Many0 => "Many0",
ErrorKind::Many1 => "Many1",
ErrorKind::Count => "Count",
ErrorKind::TakeUntil => "Take until",
ErrorKind::LengthValue => "Length followed by value",
ErrorKind::TagClosure => "Tag closure",
ErrorKind::Alpha => "Alphabetic",
ErrorKind::Digit => "Digit",
ErrorKind::AlphaNumeric => "AlphaNumeric",
ErrorKind::Space => "Space",
ErrorKind::MultiSpace => "Multiple spaces",
ErrorKind::LengthValueFn => "LengthValueFn",
ErrorKind::Eof => "End of file",
ErrorKind::Switch => "Switch",
ErrorKind::TagBits => "Tag on bitstream",
ErrorKind::OneOf => "OneOf",
ErrorKind::NoneOf => "NoneOf",
ErrorKind::Char => "Char",
ErrorKind::CrLf => "CrLf",
ErrorKind::RegexpMatch => "RegexpMatch",
ErrorKind::RegexpMatches => "RegexpMatches",
ErrorKind::RegexpFind => "RegexpFind",
ErrorKind::RegexpCapture => "RegexpCapture",
ErrorKind::RegexpCaptures => "RegexpCaptures",
ErrorKind::TakeWhile1 => "TakeWhile1",
ErrorKind::Complete => "Complete",
ErrorKind::Fix => "Fix",
ErrorKind::Escaped => "Escaped",
ErrorKind::EscapedTransform => "EscapedTransform",
ErrorKind::NonEmpty => "NonEmpty",
ErrorKind::ManyMN => "Many(m, n)",
ErrorKind::HexDigit => "Hexadecimal Digit",
ErrorKind::OctDigit => "Octal digit",
ErrorKind::Not => "Negation",
ErrorKind::Permutation => "Permutation",
ErrorKind::ManyTill => "ManyTill",
ErrorKind::Verify => "predicate verification",
ErrorKind::TakeTill1 => "TakeTill1",
ErrorKind::TakeWhileMN => "TakeWhileMN",
ErrorKind::TooLarge => "Needed data size is too large",
ErrorKind::Many0Count => "Count occurrence of >=0 patterns",
ErrorKind::Many1Count => "Count occurrence of >=1 patterns",
ErrorKind::Float => "Float",
ErrorKind::Satisfy => "Satisfy",
ErrorKind::Fail => "Fail",
}
}
}
/// Creates a parse error from a `nom::ErrorKind`
/// and the position in the input
#[allow(unused_variables)]
#[macro_export(local_inner_macros)]
macro_rules! error_position(
($input:expr, $code:expr) => ({
$crate::error::make_error($input, $code)
});
);
/// Creates a parse error from a `nom::ErrorKind`,
/// the position in the input and the next error in
/// the parsing tree
#[allow(unused_variables)]
#[macro_export(local_inner_macros)]
macro_rules! error_node_position(
($input:expr, $code:expr, $next:expr) => ({
$crate::error::append_error($input, $code, $next)
});
);
/// Prints a message and the input if the parser fails.
///
/// The message prints the `Error` or `Incomplete`
/// and the parser's calling code.
///
/// It also displays the input in hexdump format
///
/// ```rust
/// use nom::{IResult, error::dbg_dmp, bytes::complete::tag};
///
/// fn f(i: &[u8]) -> IResult<&[u8], &[u8]> {
/// dbg_dmp(tag("abcd"), "tag")(i)
/// }
///
/// let a = &b"efghijkl"[..];
///
/// // Will print the following message:
/// // Error(Position(0, [101, 102, 103, 104, 105, 106, 107, 108])) at l.5 by ' tag ! ( "abcd" ) '
/// // 00000000 65 66 67 68 69 6a 6b 6c efghijkl
/// f(a);
/// ```
#[cfg(feature = "std")]
#[cfg_attr(feature = "docsrs", doc(cfg(feature = "std")))]
pub fn dbg_dmp<'a, F, O, E: std::fmt::Debug>(
f: F,
context: &'static str,
) -> impl Fn(&'a [u8]) -> IResult<&'a [u8], O, E>
where
F: Fn(&'a [u8]) -> IResult<&'a [u8], O, E>,
{
use crate::HexDisplay;
move |i: &'a [u8]| match f(i) {
Err(e) => {
println!("{}: Error({:?}) at:\n{}", context, e, i.to_hex(8));
Err(e)
}
a => a,
}
}
#[cfg(test)]
#[cfg(feature = "alloc")]
mod tests {
use super::*;
use crate::character::complete::char;
#[test]
fn convert_error_panic() {
let input = "";
let _result: IResult<_, _, VerboseError<&str>> = char('x')(input);
}
}
/*
#[cfg(feature = "alloc")]
use lib::std::{vec::Vec, collections::HashMap};
#[cfg(feature = "std")]
use lib::std::hash::Hash;
#[cfg(feature = "std")]
pub fn add_error_pattern<'a, I: Clone + Hash + Eq, O, E: Clone + Hash + Eq>(
h: &mut HashMap, &'a str>,
e: VerboseError,
message: &'a str,
) -> bool {
h.insert(e, message);
true
}
pub fn slice_to_offsets(input: &[u8], s: &[u8]) -> (usize, usize) {
let start = input.as_ptr();
let off1 = s.as_ptr() as usize - start as usize;
let off2 = off1 + s.len();
(off1, off2)
}
#[cfg(feature = "std")]
pub fn prepare_errors(input: &[u8], e: VerboseError<&[u8]>) -> Option> {
let mut v: Vec<(ErrorKind, usize, usize)> = Vec::new();
for (p, kind) in e.errors.drain(..) {
let (o1, o2) = slice_to_offsets(input, p);
v.push((kind, o1, o2));
}
v.reverse();
Some(v)
}
#[cfg(feature = "std")]
pub fn print_error(input: &[u8], res: VerboseError<&[u8]>) {
if let Some(v) = prepare_errors(input, res) {
let colors = generate_colors(&v);
println!("parser codes: {}", print_codes(&colors, &HashMap::new()));
println!("{}", print_offsets(input, 0, &v));
} else {
println!("not an error");
}
}
#[cfg(feature = "std")]
pub fn generate_colors(v: &[(ErrorKind, usize, usize)]) -> HashMap {
let mut h: HashMap = HashMap::new();
let mut color = 0;
for &(ref c, _, _) in v.iter() {
h.insert(error_to_u32(c), color + 31);
color = color + 1 % 7;
}
h
}
pub fn code_from_offset(v: &[(ErrorKind, usize, usize)], offset: usize) -> Option {
let mut acc: Option<(u32, usize, usize)> = None;
for &(ref ek, s, e) in v.iter() {
let c = error_to_u32(ek);
if s <= offset && offset <= e {
if let Some((_, start, end)) = acc {
if start <= s && e <= end {
acc = Some((c, s, e));
}
} else {
acc = Some((c, s, e));
}
}
}
if let Some((code, _, _)) = acc {
return Some(code);
} else {
return None;
}
}
#[cfg(feature = "alloc")]
pub fn reset_color(v: &mut Vec) {
v.push(0x1B);
v.push(b'[');
v.push(0);
v.push(b'm');
}
#[cfg(feature = "alloc")]
pub fn write_color(v: &mut Vec, color: u8) {
v.push(0x1B);
v.push(b'[');
v.push(1);
v.push(b';');
let s = color.to_string();
let bytes = s.as_bytes();
v.extend(bytes.iter().cloned());
v.push(b'm');
}
#[cfg(feature = "std")]
#[cfg_attr(feature = "cargo-clippy", allow(implicit_hasher))]
pub fn print_codes(colors: &HashMap, names: &HashMap) -> String {
let mut v = Vec::new();
for (code, &color) in colors {
if let Some(&s) = names.get(code) {
let bytes = s.as_bytes();
write_color(&mut v, color);
v.extend(bytes.iter().cloned());
} else {
let s = code.to_string();
let bytes = s.as_bytes();
write_color(&mut v, color);
v.extend(bytes.iter().cloned());
}
reset_color(&mut v);
v.push(b' ');
}
reset_color(&mut v);
String::from_utf8_lossy(&v[..]).into_owned()
}
#[cfg(feature = "std")]
pub fn print_offsets(input: &[u8], from: usize, offsets: &[(ErrorKind, usize, usize)]) -> String {
let mut v = Vec::with_capacity(input.len() * 3);
let mut i = from;
let chunk_size = 8;
let mut current_code: Option = None;
let mut current_code2: Option = None;
let colors = generate_colors(&offsets);
for chunk in input.chunks(chunk_size) {
let s = format!("{:08x}", i);
for &ch in s.as_bytes().iter() {
v.push(ch);
}
v.push(b'\t');
let mut k = i;
let mut l = i;
for &byte in chunk {
if let Some(code) = code_from_offset(&offsets, k) {
if let Some(current) = current_code {
if current != code {
reset_color(&mut v);
current_code = Some(code);
if let Some(&color) = colors.get(&code) {
write_color(&mut v, color);
}
}
} else {
current_code = Some(code);
if let Some(&color) = colors.get(&code) {
write_color(&mut v, color);
}
}
}
v.push(CHARS[(byte >> 4) as usize]);
v.push(CHARS[(byte & 0xf) as usize]);
v.push(b' ');
k = k + 1;
}
reset_color(&mut v);
if chunk_size > chunk.len() {
for _ in 0..(chunk_size - chunk.len()) {
v.push(b' ');
v.push(b' ');
v.push(b' ');
}
}
v.push(b'\t');
for &byte in chunk {
if let Some(code) = code_from_offset(&offsets, l) {
if let Some(current) = current_code2 {
if current != code {
reset_color(&mut v);
current_code2 = Some(code);
if let Some(&color) = colors.get(&code) {
write_color(&mut v, color);
}
}
} else {
current_code2 = Some(code);
if let Some(&color) = colors.get(&code) {
write_color(&mut v, color);
}
}
}
if (byte >= 32 && byte <= 126) || byte >= 128 {
v.push(byte);
} else {
v.push(b'.');
}
l = l + 1;
}
reset_color(&mut v);
v.push(b'\n');
i = i + chunk_size;
}
String::from_utf8_lossy(&v[..]).into_owned()
}
*/