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//! Error management //! //! Depending on a compilation flag, the content of the `Context` enum //! can change. In the default case, it will only have one variant: //! `Context::Code(I, ErrorKind<E=u32>)` (with `I` and `E` configurable). //! It contains an error code and the input position that triggered it. //! //! If you activate the `verbose-errors` compilation flags, it will add another //! variant to the enum: `Context::List(Vec<(I, ErrorKind<E>)>)`. //! This variant aggregates positions and error codes as the code backtracks //! through the nested parsers. //! The verbose errors feature allows for very flexible error management: //! you can know precisely which parser got to which part of the input. //! The main drawback is that it is a lot slower than default error //! management. use util::{Convert, ErrorKind}; use lib::std::convert::From; #[cfg(feature = "alloc")] use lib::std::vec::Vec; /// Contains the error that a parser can return /// /// If you use the `verbose-errors` compilation feature, /// `nom::Err` will be the enum defined here, /// otherwise, it will amount to a `ErrorKind<E=u32>`. /// /// It can represent a linked list of errors, indicating the path taken in the parsing tree, with corresponding position in the input data. /// It depends on P, the input position (for a &[u8] parser, it would be a &[u8]), and E, the custom error type (by default, u32) #[derive(Debug, PartialEq, Eq, Clone)] pub enum Context<I, E = u32> { /// An error code, represented by an ErrorKind, which can contain a custom error code represented by E Code(I, ErrorKind<E>), List(Vec<(I, ErrorKind<E>)>), } impl<I, H: From<I>, F, E: From<F>> Convert<Context<I, F>> for Context<H, E> { fn convert(c: Context<I, F>) -> Self { match c { Context::Code(i, e) => Context::Code(i.into(), ErrorKind::convert(e)), Context::List(mut v) => Context::List( v.drain(..) .map(|(i, e)| (i.into(), ErrorKind::convert(e))) .collect(), ), } } } impl<I, E> Context<I, E> { /// Convert Err into ErrorKind. /// /// This allows application code to use ErrorKind and stay independent from the verbose-errors features activation. pub fn into_error_kind(self) -> ErrorKind<E> { match self { Context::Code(_, kind) => kind, Context::List(mut v) => { let (_, kind) = v.remove(0); kind } } } } /* impl<I,O,E> IResult<I,O,E> { /// Maps a `IResult<I, O, E>` to `IResult<I, O, N>` by appling a function /// to a contained `Error` value, leaving `Done` and `Incomplete` value /// untouched. #[inline] pub fn map_err<N, F>(self, f: F) -> IResult<I, O, N> where F: FnOnce(Err<I, E>) -> Err<I, N> { match self { Error(e) => Error(f(e)), Incomplete(n) => Incomplete(n), Done(i, o) => Done(i, o), } } /// Unwrap the contained `Error(I, E)` value, or panic if the `IResult` is not /// `Error`. pub fn unwrap_err(self) -> Err<I, E> { match self { Error(e) => e, Done(_, _) => panic!("unwrap_err() called on an IResult that is Done"), Incomplete(_) => panic!("unwrap_err() called on an IResult that is Incomplete"), } } /// Convert the IResult to a std::result::Result pub fn to_full_result(self) -> Result<O, IError<I,E>> { match self { Done(_, o) => Ok(o), Incomplete(n) => Err(IError::Incomplete(n)), Error(e) => Err(IError::Error(e)) } } /// Convert the IResult to a std::result::Result pub fn to_result(self) -> Result<O, Err<I,E>> { match self { Done(_, o) => Ok(o), Error(e) => Err(e), Incomplete(_) => panic!("to_result() called on an IResult that is Incomplete") } } } #[cfg(feature = "std")] use $crate::lib::std::any::Any; #[cfg(feature = "std")] use $crate::lib::std::{error,fmt}; #[cfg(feature = "std")] use $crate::lib::std::fmt::Debug; #[cfg(feature = "std")] impl<P:Debug+Any,E:Debug+Any> error::Error for Err<P,E> { fn description(&self) -> &str { let kind = match *self { Err::Code(ref e) | Err::Node(ref e, _) | Err::Position(ref e, _) | Err::NodePosition(ref e, _, _) => e }; kind.description() } } #[cfg(feature = "std")] impl<P:fmt::Debug,E:fmt::Debug> fmt::Display for Err<P,E> { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { match *self { Err::Code(ref e) | Err::Node(ref e, _) => { write!(f, "{:?}", e) }, Err::Position(ref e, ref p) | Err::NodePosition(ref e, ref p, _) => { write!(f, "{:?}:{:?}", p, e) } } } } */ /// translate parser result from IResult<I,O,u32> to IResult<I,O,E> with a custom type /// /// ``` /// # #[macro_use] extern crate nom; /// # use nom::ErrorKind; /// # use nom::Context; /// # use nom::Err; /// # fn main() { /// #[derive(Debug,Clone,PartialEq)] /// pub struct ErrorStr(String); /// /// // Convert to IResult<&[u8], &[u8], ErrorStr> /// impl From<u32> for ErrorStr { /// fn from(i: u32) -> Self { /// ErrorStr(format!("custom error code: {}", i)) /// } /// } /// /// // will add a Custom(42) error to the error chain /// named!(err_test, add_return_error!(ErrorKind::Custom(42), tag!("abcd"))); /// /// // Convert to IResult<&[u8], &[u8], ErrorStr> /// named!(parser<&[u8], &[u8], ErrorStr>, fix_error!(ErrorStr, err_test)); /// /// let a = &b"efghblah"[..]; /// //assert_eq!(parser(a), Err(Err::Error(Context::Code(a, ErrorKind::Custom(ErrorStr("custom error code: 42".to_string())))))); /// let list = vec!((a, ErrorKind::Tag), (a, ErrorKind::Custom(ErrorStr("custom error code: 42".to_string())))); /// assert_eq!( /// parser(a), /// Err(Err::Error(Context::List(list))) /// ); /// # } /// ``` #[macro_export(local_inner_macros)] macro_rules! fix_error ( ($i:expr, $t:ty, $submac:ident!( $($args:tt)* )) => ( { use $crate::lib::std::result::Result::*; use $crate::{Err,Convert,ErrorKind,Context}; match $submac!($i, $($args)*) { Err(e) => { let e2 = match e { Err::Error(err) => { let err2 = match err { Context::Code(i, code) => { let code2: ErrorKind<$t> = ErrorKind::convert(code); Context::Code(i, code2) }, Context::List(mut v) => { Context::List(v.drain(..).map(|(i, code)| { let code2: ErrorKind<$t> = ErrorKind::convert(code); (i, code2) }).collect()) } }; Err::Error(err2) }, Err::Failure(err) => { let err2 = match err { Context::Code(i, code) => { let code2: ErrorKind<$t> = ErrorKind::convert(code); Context::Code(i, code2) }, Context::List(mut v) => { Context::List(v.drain(..).map(|(i, code)| { let code2: ErrorKind<$t> = ErrorKind::convert(code); (i, code2) }).collect()) } }; Err::Failure(err2) }, Err::Incomplete(i) => Err::Incomplete(i), }; Err(e2) }, Ok((i, o)) => Ok((i, o)), } } ); ($i:expr, $t:ty, $f:expr) => ( fix_error!($i, $t, call!($f)); ); ); /// `flat_map!(R -> IResult<R,S>, S -> IResult<S,T>) => R -> IResult<R, T>` /// /// combines a parser R -> IResult<R,S> and /// a parser S -> IResult<S,T> to return another /// parser R -> IResult<R,T> #[macro_export(local_inner_macros)] macro_rules! flat_map( ($i:expr, $submac:ident!( $($args:tt)* ), $submac2:ident!( $($args2:tt)* )) => ( flat_map!(__impl $i, $submac!($($args)*), $submac2!($($args2)*)); ); ($i:expr, $submac:ident!( $($args:tt)* ), $g:expr) => ( flat_map!(__impl $i, $submac!($($args)*), call!($g)); ); ($i:expr, $f:expr, $submac:ident!( $($args:tt)* )) => ( flat_map!(__impl $i, call!($f), $submac!($($args)*)); ); ($i:expr, $f:expr, $g:expr) => ( flat_map!(__impl $i, call!($f), call!($g)); ); (__impl $i:expr, $submac:ident!( $($args:tt)* ), $submac2:ident!( $($args2:tt)* )) => ( { use $crate::lib::std::result::Result::*; use $crate::{Err,Convert}; ($submac!($i, $($args)*)).and_then(|(i,o)| { match $submac2!(o, $($args2)*) { Err(e) => Err(Err::convert(e)), Ok((_, o2)) => Ok((i, o2)) } }) } ); );