[−][src]Enum nom_supreme::error::ErrorTree
A comprehensive tree of nom errors describing a parse failure.
This Error type is designed to be VerboseError
++
. While
VerboseError
can represent a stack of errors, this type can represent
a full tree. In addition to representing a particular specific parse error,
it can also represent a stack of nested error contexts (for instance, as
provided by context
), or a list of alternatives
that were all tried individually by alt
and all failed.
In general, the design goal for this type is to discard as little useful
information as possible. That being said, many ErrorKind
variants add
very little useful contextual information to error traces; for example,
ErrorKind::Alt
doesn't add any interesting context to an
ErrorTree::Alt
, and its presence in a stack precludes merging together
adjacent sets of ErrorTree::Alt
siblings.
Examples
Base parser errors
An ErrorTree::Base
is an error that occurred at the "bottom" of the stack,
from a parser looking for 1 specific kind of thing.
use cool_asserts::assert_matches; use nom::{Parser, Err}; use nom::character::complete::{digit1, char}; use nom_supreme::error::{ErrorTree, BaseErrorKind, StackContext, Expectation}; use nom_supreme::parser_ext::ParserExt; let err: Err<ErrorTree<&str>> = digit1.parse("abc").unwrap_err(); assert_matches!(err, Err::Error(ErrorTree::Base{ location: "abc", kind: BaseErrorKind::Expected(Expectation::Digit), })); let err: Err<ErrorTree<&str>> = char('a').and(char('b')).parse("acb").unwrap_err(); assert_matches!(err, Err::Error(ErrorTree::Base{ location: "cb", kind: BaseErrorKind::Expected(Expectation::Char('b')), }));
Stacks
An ErrorTree::Stack
is created when a parser combinator—typically
context
—attaches additional error context to a subparser error. It can
have any ErrorTree
at the base of the stack.
use cool_asserts::assert_matches; use nom::{Parser, Err}; use nom::character::complete::{alpha1, space1, char,}; use nom::sequence::{separated_pair, delimited}; use nom_supreme::parser_ext::ParserExt; use nom_supreme::error::{ErrorTree, BaseErrorKind, StackContext, Expectation}; // Parse a single identifier, defined as just a string of letters. let identifier = alpha1.context("identifier"); // Parse a pair of identifiers, separated by whitespace let identifier_pair = separated_pair(identifier, space1, identifier) .context("identifier pair"); // Parse a pair of identifiers in parenthesis. let mut parenthesized = delimited(char('('), identifier_pair, char(')')) .context("parenthesized"); let err: Err<ErrorTree<&str>> = parenthesized.parse("(abc 123)").unwrap_err(); assert_matches!(err, Err::Error(ErrorTree::Stack { base, contexts, }) => { assert_matches!(*base, ErrorTree::Base { location: "123)", kind: BaseErrorKind::Expected(Expectation::Alpha) }); assert_eq!(contexts, [ ("123)", StackContext::Context("identifier")), ("abc 123)", StackContext::Context("identifier pair")), ("(abc 123)", StackContext::Context("parenthesized")), ]); });
Alternatives
An ErrorTree::Alt
is created when a series of parsers are all tried,
and all of them fail. Most commonly this will happen via the alt
combinator or the equivalent .or
postfix combinator. When all of these
subparsers fail, their errors (each individually their own ErrorTree
) are
aggregated into an ErrorTree::Alt
, indicating that "any one of these
things were expected."
use cool_asserts::assert_matches; use nom::{Parser, Err}; use nom::branch::alt; use nom_supreme::error::{ErrorTree, BaseErrorKind, StackContext, Expectation}; use nom_supreme::parser_ext::ParserExt; use nom_supreme::tag::complete::tag; let parse_bool = alt(( tag("true").value(true), tag("false").value(true), )); let mut parse_null_bool = alt(( parse_bool.map(Some), tag("null").value(None), )); let err: Err<ErrorTree<&str>> = parse_null_bool.parse("123").unwrap_err(); // This error communicates to the caller that any one of "true", "false", // or "null" was expected at that location. assert_matches!(err, Err::Error(ErrorTree::Alt(choices)) => { assert_matches!(choices.as_slice(), [ ErrorTree::Base { location: "123", kind: BaseErrorKind::Expected(Expectation::Tag("true"))}, ErrorTree::Base { location: "123", kind: BaseErrorKind::Expected(Expectation::Tag("false"))}, ErrorTree::Base { location: "123", kind: BaseErrorKind::Expected(Expectation::Tag("null"))}, ]) });
Contexts and Alternatives
Because Stack
and Alt
recursively contain ErrorTree
errors from
subparsers, they can be can combined to create error trees of arbitrary
complexity.
use cool_asserts::assert_matches; use nom::{Parser, Err}; use nom::branch::alt; use nom_supreme::error::{ErrorTree, BaseErrorKind, StackContext, Expectation}; use nom_supreme::parser_ext::ParserExt; use nom_supreme::tag::complete::tag; let parse_bool = alt(( tag("true").value(true), tag("false").value(true), )).context("bool"); let mut parse_null_bool = alt(( parse_bool.map(Some), tag("null").value(None).context("null"), )).context("null or bool"); let err: Err<ErrorTree<&str>> = parse_null_bool.parse("123").unwrap_err(); assert_matches!(err, Err::Error(ErrorTree::Stack{base, contexts}) => { assert_eq!(contexts, [("123", StackContext::Context("null or bool"))]); assert_matches!(*base, ErrorTree::Alt(choices) => { assert_matches!(&choices[0], ErrorTree::Stack{base, contexts} => { assert_eq!(contexts, &[("123", StackContext::Context("bool"))]); assert_matches!(&**base, ErrorTree::Alt(choices) => { assert_matches!(&choices[0], ErrorTree::Base { location: "123", kind: BaseErrorKind::Expected(Expectation::Tag("true")) }); assert_matches!(&choices[1], ErrorTree::Base { location: "123", kind: BaseErrorKind::Expected(Expectation::Tag("false")) }); }); }); assert_matches!(&choices[1], ErrorTree::Stack{base, contexts} => { assert_eq!(contexts, &[("123", StackContext::Context("null"))]); assert_matches!(&**base, ErrorTree::Base { location: "123", kind: BaseErrorKind::Expected(Expectation::Tag("null")) }); }); }); });
Display formatting
TODO WRITE THIS SECTION
Variants
A specific error event at a specific location. Often this will indicate that something like a tag or character was expected at that location. When used as part of a stack, it indicates some additional context for the root error of the stack.
Fields of Base
location: I
The location of this error in the input
kind: BaseErrorKind
The specific error that occurred
A stack indicates a chain of error contexts was provided. The stack
should be read "backwards"; that is, errors earlier in the Vec
occurred "sooner" (deeper in the call stack).
Fields of Stack
base: Box<Self>
The original error
contexts: Vec<(I, StackContext)>
The stack of contexts attached to that error
Alt(Vec<Self>)
A series of parsers were tried in order at the same location (for
instance, via the alt
combinator) and all of
them failed. All of the errors in this set are "siblings".
Implementations
impl<I> ErrorTree<I>
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pub fn map_locations<T>(
self,
convert_location: impl FnMut(I) -> T
) -> ErrorTree<T>
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self,
convert_location: impl FnMut(I) -> T
) -> ErrorTree<T>
Convert all of the locations in this error using some kind of mapping function. This is intended to help add additional context that may not have been available when the nom parsers were running, such as line and column numbers.
Trait Implementations
impl<I> ContextError<I> for ErrorTree<I>
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pub fn add_context(location: I, ctx: &'static str, other: Self) -> Self
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Similar to append: Create a new error with some added context
impl<I: Debug> Debug for ErrorTree<I>
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impl<I: Display> Display for ErrorTree<I>
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impl<I: Display + Debug> Error for ErrorTree<I>
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pub fn source(&self) -> Option<&(dyn Error + 'static)>
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pub fn backtrace(&self) -> Option<&Backtrace>
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pub fn description(&self) -> &str
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pub fn cause(&self) -> Option<&dyn Error>
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impl<I, T> ExtractContext<I, ErrorTree<T>> for ErrorTree<I> where
I: Clone,
T: RecreateContext<I>,
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I: Clone,
T: RecreateContext<I>,
pub fn extract_context(self, original_input: I) -> ErrorTree<T>
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impl<I, E: Error + Send + Sync + 'static> FromExternalError<I, E> for ErrorTree<I>
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pub fn from_external_error(location: I, _kind: NomErrorKind, e: E) -> Self
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Create an error from a given external error, such as from FromStr
impl<I: InputLength> ParseError<I> for ErrorTree<I>
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pub fn from_error_kind(location: I, kind: NomErrorKind) -> Self
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Create a new error at the given position. Interpret kind
as an
Expectation
if possible, to give a more informative error message.
pub fn append(location: I, kind: NomErrorKind, other: Self) -> Self
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Combine an existing error with a new one. This is how error context is accumulated when backtracing. "other" is the original error, and the inputs new error from higher in the call stack.
If other
is already an ErrorTree::Stack
, the context is added to
the stack; otherwise, a new stack is created, with other
at the root.
pub fn from_char(location: I, character: char) -> Self
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Create an error indicating an expected character at a given position
pub fn or(self, other: Self) -> Self
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Combine two errors from branches of alt. If either or both errors are
already ErrorTree::Alt
, the different error sets are merged;
otherwise, a new ErrorTree::Alt
is created, containing both
self
and other
.
impl<I> TagError<I, &'static str> for ErrorTree<I>
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pub fn from_tag(location: I, tag: &'static str) -> Self
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pub fn from_tag_no_case(input: I, tag: T) -> Self
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Auto Trait Implementations
impl<I> !RefUnwindSafe for ErrorTree<I>
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impl<I> Send for ErrorTree<I> where
I: Send,
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I: Send,
impl<I> Sync for ErrorTree<I> where
I: Sync,
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I: Sync,
impl<I> Unpin for ErrorTree<I> where
I: Unpin,
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I: Unpin,
impl<I> !UnwindSafe for ErrorTree<I>
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Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
pub fn borrow_mut(&mut self) -> &mut T
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impl<T> Conv for T
impl<T> Conv for T
impl<I, T> ExtractContext<I, ()> for T
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pub fn extract_context(Self, I)
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impl<T> FmtForward for T
pub fn fmt_binary(self) -> FmtBinary<Self> where
Self: Binary,
Self: Binary,
pub fn fmt_display(self) -> FmtDisplay<Self> where
Self: Display,
Self: Display,
pub fn fmt_lower_exp(self) -> FmtLowerExp<Self> where
Self: LowerExp,
Self: LowerExp,
pub fn fmt_lower_hex(self) -> FmtLowerHex<Self> where
Self: LowerHex,
Self: LowerHex,
pub fn fmt_octal(self) -> FmtOctal<Self> where
Self: Octal,
Self: Octal,
pub fn fmt_pointer(self) -> FmtPointer<Self> where
Self: Pointer,
Self: Pointer,
pub fn fmt_upper_exp(self) -> FmtUpperExp<Self> where
Self: UpperExp,
Self: UpperExp,
pub fn fmt_upper_hex(self) -> FmtUpperHex<Self> where
Self: UpperHex,
Self: UpperHex,
impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T> Pipe for T where
T: ?Sized,
T: ?Sized,
pub fn pipe<R>(self, func: impl FnOnce(Self) -> R) -> R
pub fn pipe_ref<'a, R>(&'a self, func: impl FnOnce(&'a Self) -> R) -> R where
R: 'a,
R: 'a,
pub fn pipe_ref_mut<'a, R>(
&'a mut self,
func: impl FnOnce(&'a mut Self) -> R
) -> R where
R: 'a,
&'a mut self,
func: impl FnOnce(&'a mut Self) -> R
) -> R where
R: 'a,
pub fn pipe_borrow<'a, B, R>(&'a self, func: impl FnOnce(&'a B) -> R) -> R where
Self: Borrow<B>,
B: 'a + ?Sized,
R: 'a,
Self: Borrow<B>,
B: 'a + ?Sized,
R: 'a,
pub fn pipe_borrow_mut<'a, B, R>(
&'a mut self,
func: impl FnOnce(&'a mut B) -> R
) -> R where
Self: BorrowMut<B>,
B: 'a + ?Sized,
R: 'a,
&'a mut self,
func: impl FnOnce(&'a mut B) -> R
) -> R where
Self: BorrowMut<B>,
B: 'a + ?Sized,
R: 'a,
pub fn pipe_as_ref<'a, U, R>(&'a self, func: impl FnOnce(&'a U) -> R) -> R where
Self: AsRef<U>,
R: 'a,
U: 'a + ?Sized,
Self: AsRef<U>,
R: 'a,
U: 'a + ?Sized,
pub fn pipe_as_mut<'a, U, R>(
&'a mut self,
func: impl FnOnce(&'a mut U) -> R
) -> R where
Self: AsMut<U>,
R: 'a,
U: 'a + ?Sized,
&'a mut self,
func: impl FnOnce(&'a mut U) -> R
) -> R where
Self: AsMut<U>,
R: 'a,
U: 'a + ?Sized,
pub fn pipe_deref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: Deref<Target = T>,
T: 'a + ?Sized,
R: 'a,
Self: Deref<Target = T>,
T: 'a + ?Sized,
R: 'a,
pub fn pipe_deref_mut<'a, T, R>(
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: DerefMut<Target = T> + Deref,
T: 'a + ?Sized,
R: 'a,
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: DerefMut<Target = T> + Deref,
T: 'a + ?Sized,
R: 'a,
impl<T> Pipe for T
impl<T> PipeAsRef for T
pub fn pipe_as_ref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: AsRef<T>,
T: 'a,
R: 'a,
Self: AsRef<T>,
T: 'a,
R: 'a,
pub fn pipe_as_mut<'a, T, R>(
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: AsMut<T>,
T: 'a,
R: 'a,
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: AsMut<T>,
T: 'a,
R: 'a,
impl<T> PipeBorrow for T
pub fn pipe_borrow<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R where
Self: Borrow<T>,
T: 'a,
R: 'a,
Self: Borrow<T>,
T: 'a,
R: 'a,
pub fn pipe_borrow_mut<'a, T, R>(
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: BorrowMut<T>,
T: 'a,
R: 'a,
&'a mut self,
func: impl FnOnce(&'a mut T) -> R
) -> R where
Self: BorrowMut<T>,
T: 'a,
R: 'a,
impl<T> PipeDeref for T
pub fn pipe_deref<'a, R>(
&'a self,
func: impl FnOnce(&'a Self::Target) -> R
) -> R where
Self: Deref,
R: 'a,
&'a self,
func: impl FnOnce(&'a Self::Target) -> R
) -> R where
Self: Deref,
R: 'a,
pub fn pipe_deref_mut<'a, R>(
&'a mut self,
func: impl FnOnce(&'a mut Self::Target) -> R
) -> R where
Self: DerefMut,
R: 'a,
&'a mut self,
func: impl FnOnce(&'a mut Self::Target) -> R
) -> R where
Self: DerefMut,
R: 'a,
impl<T> PipeRef for T
pub fn pipe_ref<'a, R>(&'a self, func: impl FnOnce(&'a Self) -> R) -> R where
R: 'a,
R: 'a,
pub fn pipe_mut<'a, R>(&'a mut self, func: impl FnOnce(&'a mut Self) -> R) -> R where
R: 'a,
R: 'a,
impl<I> RecreateContext<I> for I
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pub fn recreate_context(I, I) -> I
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impl<T> Tap for T
pub fn tap(self, func: impl FnOnce(&Self)) -> Self
pub fn tap_mut(self, func: impl FnOnce(&mut Self)) -> Self
pub fn tap_borrow<B>(self, func: impl FnOnce(&B)) -> Self where
Self: Borrow<B>,
B: ?Sized,
Self: Borrow<B>,
B: ?Sized,
pub fn tap_borrow_mut<B>(self, func: impl FnOnce(&mut B)) -> Self where
Self: BorrowMut<B>,
B: ?Sized,
Self: BorrowMut<B>,
B: ?Sized,
pub fn tap_ref<R>(self, func: impl FnOnce(&R)) -> Self where
Self: AsRef<R>,
R: ?Sized,
Self: AsRef<R>,
R: ?Sized,
pub fn tap_ref_mut<R>(self, func: impl FnOnce(&mut R)) -> Self where
Self: AsMut<R>,
R: ?Sized,
Self: AsMut<R>,
R: ?Sized,
pub fn tap_deref<T>(self, func: impl FnOnce(&T)) -> Self where
Self: Deref<Target = T>,
T: ?Sized,
Self: Deref<Target = T>,
T: ?Sized,
pub fn tap_deref_mut<T>(self, func: impl FnOnce(&mut T)) -> Self where
Self: DerefMut<Target = T> + Deref,
T: ?Sized,
Self: DerefMut<Target = T> + Deref,
T: ?Sized,
pub fn tap_dbg(self, func: impl FnOnce(&Self)) -> Self
pub fn tap_mut_dbg(self, func: impl FnOnce(&mut Self)) -> Self
pub fn tap_borrow_dbg<B>(self, func: impl FnOnce(&B)) -> Self where
Self: Borrow<B>,
B: ?Sized,
Self: Borrow<B>,
B: ?Sized,
pub fn tap_borrow_mut_dbg<B>(self, func: impl FnOnce(&mut B)) -> Self where
Self: BorrowMut<B>,
B: ?Sized,
Self: BorrowMut<B>,
B: ?Sized,
pub fn tap_ref_dbg<R>(self, func: impl FnOnce(&R)) -> Self where
Self: AsRef<R>,
R: ?Sized,
Self: AsRef<R>,
R: ?Sized,
pub fn tap_ref_mut_dbg<R>(self, func: impl FnOnce(&mut R)) -> Self where
Self: AsMut<R>,
R: ?Sized,
Self: AsMut<R>,
R: ?Sized,
pub fn tap_deref_dbg<T>(self, func: impl FnOnce(&T)) -> Self where
Self: Deref<Target = T>,
T: ?Sized,
Self: Deref<Target = T>,
T: ?Sized,
pub fn tap_deref_mut_dbg<T>(self, func: impl FnOnce(&mut T)) -> Self where
Self: DerefMut<Target = T> + Deref,
T: ?Sized,
Self: DerefMut<Target = T> + Deref,
T: ?Sized,
impl<T> Tap for T
pub fn tap<F, R>(self, func: F) -> Self where
F: FnOnce(&Self) -> R,
F: FnOnce(&Self) -> R,
pub fn tap_dbg<F, R>(self, func: F) -> Self where
F: FnOnce(&Self) -> R,
F: FnOnce(&Self) -> R,
pub fn tap_mut<F, R>(self, func: F) -> Self where
F: FnOnce(&mut Self) -> R,
F: FnOnce(&mut Self) -> R,
pub fn tap_mut_dbg<F, R>(self, func: F) -> Self where
F: FnOnce(&mut Self) -> R,
F: FnOnce(&mut Self) -> R,
impl<T, U> TapAsRef<U> for T where
U: ?Sized,
U: ?Sized,
pub fn tap_ref<F, R>(self, func: F) -> Self where
Self: AsRef<T>,
F: FnOnce(&T) -> R,
Self: AsRef<T>,
F: FnOnce(&T) -> R,
pub fn tap_ref_dbg<F, R>(self, func: F) -> Self where
Self: AsRef<T>,
F: FnOnce(&T) -> R,
Self: AsRef<T>,
F: FnOnce(&T) -> R,
pub fn tap_ref_mut<F, R>(self, func: F) -> Self where
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
pub fn tap_ref_mut_dbg<F, R>(self, func: F) -> Self where
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
Self: AsMut<T>,
F: FnOnce(&mut T) -> R,
impl<T, U> TapBorrow<U> for T where
U: ?Sized,
U: ?Sized,
pub fn tap_borrow<F, R>(self, func: F) -> Self where
Self: Borrow<T>,
F: FnOnce(&T) -> R,
Self: Borrow<T>,
F: FnOnce(&T) -> R,
pub fn tap_borrow_dbg<F, R>(self, func: F) -> Self where
Self: Borrow<T>,
F: FnOnce(&T) -> R,
Self: Borrow<T>,
F: FnOnce(&T) -> R,
pub fn tap_borrow_mut<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
pub fn tap_borrow_mut_dbg<F, R>(self, func: F) -> Self where
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
Self: BorrowMut<T>,
F: FnOnce(&mut T) -> R,
impl<T> TapDeref for T
pub fn tap_deref<F, R>(self, func: F) -> Self where
Self: Deref,
F: FnOnce(&Self::Target) -> R,
Self: Deref,
F: FnOnce(&Self::Target) -> R,
pub fn tap_deref_dbg<F, R>(self, func: F) -> Self where
Self: Deref,
F: FnOnce(&Self::Target) -> R,
Self: Deref,
F: FnOnce(&Self::Target) -> R,
pub fn tap_deref_mut<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
pub fn tap_deref_mut_dbg<F, R>(self, func: F) -> Self where
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
Self: DerefMut,
F: FnOnce(&mut Self::Target) -> R,
impl<T> ToString for T where
T: Display + ?Sized,
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T: Display + ?Sized,
impl<T> TryConv for T
impl<T> TryConv for T
impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,