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//! Enhanced tag parser for nom.
//!
//! This module introduces a new trait, [`TagError`], and variants of `tag`
//! and `tag_case_insensitive` that can use the trait to add to an error the
//! specific tag that was expected. This allows the error message to report
//! something like `Expected tag: "true"` instead of just `Error: Tag`.
use nom::error::{Error, ErrorKind, ParseError, VerboseError};
/// Similar to [`FromExternalError`][nom::error::FromExternalError] and
/// [`ContextError`][nom::error::ContextError], this trait allows a parser to
/// create an error representing an unmatched tag. This allows error messages
/// to produce more useful context about what went wrong.
pub trait TagError<I, T>: Sized {
/// Create an error from an expected tag at a location.
fn from_tag(input: I, tag: T) -> Self;
/// As above, but for a case insensitive tag. By default this just
/// calls [`from_tag`][Self::from_tag]
fn from_tag_no_case(input: I, tag: T) -> Self {
Self::from_tag(input, tag)
}
}
impl<I, T> TagError<I, T> for () {
fn from_tag(_input: I, _tag: T) {}
}
impl<I, T> TagError<I, T> for (I, ErrorKind) {
fn from_tag(input: I, _tag: T) -> Self {
(input, ErrorKind::Tag)
}
}
impl<I, T> TagError<I, T> for Error<I> {
fn from_tag(input: I, _tag: T) -> Self {
Error::new(input, ErrorKind::Tag)
}
}
impl<I, T> TagError<I, T> for VerboseError<I> {
fn from_tag(input: I, _tag: T) -> Self {
VerboseError::from_error_kind(input, ErrorKind::Tag)
}
}
/// Complete input version of enhanced `tag` parsers
pub mod complete {
use nom::{Compare, CompareResult, Err, IResult, InputLength, InputTake};
use super::TagError;
/// Parser recognizing a fixed pattern, called a tag. If the front of the
/// input data matches the `tag`, that part of the input will be returned.
/// Records the tag in the error in the event of a parse failure via
/// [`TagError`].
///
/// # Example
///
/// ```
/// # use nom::{IResult, Err, Needed};
/// use cool_asserts::assert_matches;
/// use nom_supreme::tag::complete::tag;
/// use nom_supreme::error::{ErrorTree, BaseErrorKind, Expectation};
///
/// fn parse_hello(s: &str) -> IResult<&str, &str, ErrorTree<&str>> {
/// tag("hello")(s)
/// }
///
/// assert_matches!(
/// parse_hello("hello, world!"),
/// Ok((", world!", "hello")),
/// );
///
/// assert_matches!(
/// parse_hello("something"),
/// Err(Err::Error(ErrorTree::Base {
/// location: "something",
/// kind: BaseErrorKind::Expected(Expectation::Tag("hello")),
/// }))
/// );
///
/// assert_matches!(
/// parse_hello("hel"),
/// Err(Err::Error(ErrorTree::Base {
/// location: "hel",
/// kind: BaseErrorKind::Expected(Expectation::Tag("hello")),
/// }))
/// );
/// ```
pub fn tag<T, I, E>(tag: T) -> impl Clone + Fn(I) -> IResult<I, I, E>
where
T: InputLength + Clone,
I: InputTake + Compare<T>,
E: TagError<I, T>,
{
let tag_len = tag.input_len();
move |input: I| match input.compare(tag.clone()) {
CompareResult::Ok => Ok(input.take_split(tag_len)),
_ => Err(Err::Error(E::from_tag(input, tag.clone()))),
}
}
/// Parser recognizing a fixed pattern, called a tag. If the front of the
/// input data matches the `tag`, case insensitively, that part of the
/// input will be returned. Records the tag in the error in the event of a
/// parse failure via [`TagError`].
///
/// # Example
///
/// ```
/// # use nom::{IResult, Err, Needed};
/// use cool_asserts::assert_matches;
/// use nom_supreme::tag::complete::tag_no_case;
/// use nom_supreme::error::{ErrorTree, BaseErrorKind, Expectation};
///
/// fn parse_hello(s: &str) -> IResult<&str, &str, ErrorTree<&str>> {
/// tag_no_case("hello")(s)
/// }
///
/// assert_matches!(
/// parse_hello("HELLO, WORLD!"),
/// Ok((", WORLD!", "HELLO")),
/// );
///
/// assert_matches!(
/// parse_hello("something"),
/// Err(Err::Error(ErrorTree::Base {
/// location: "something",
/// kind: BaseErrorKind::Expected(Expectation::Tag("hello")),
/// }))
/// );
///
/// assert_matches!(
/// parse_hello("HEL"),
/// Err(Err::Error(ErrorTree::Base {
/// location: "HEL",
/// kind: BaseErrorKind::Expected(Expectation::Tag("hello")),
/// }))
/// );
/// ```
pub fn tag_no_case<T, I, E>(tag: T) -> impl Clone + Fn(I) -> IResult<I, I, E>
where
T: InputLength + Clone,
I: InputTake + Compare<T>,
E: TagError<I, T>,
{
move |input: I| match input.compare_no_case(tag.clone()) {
CompareResult::Ok => Ok(input.take_split(tag.input_len())),
_ => Err(Err::Error(E::from_tag_no_case(input, tag.clone()))),
}
}
}
/// Streaming version of enhanced `tag` parsers.
pub mod streaming {
use nom::{Compare, CompareResult, Err, IResult, InputLength, InputTake, Needed};
use super::TagError;
/// Parser recognizing a fixed pattern, called a tag. If the front of the
/// input data matches the `tag`, that part of the input will be returned.
/// Records the tag in the error in the event of a parse failure via
/// [`TagError`]. If there is only a partial match, returns
/// [`Err::Incomplete`][nom::Err::Incomplete].
///
/// # Example
///
/// ```
/// # use nom::{IResult, Err, Needed};
/// use cool_asserts::assert_matches;
/// use nom_supreme::tag::streaming::tag;
/// use nom_supreme::error::{ErrorTree, BaseErrorKind, Expectation};
///
/// fn parse_hello(s: &str) -> IResult<&str, &str, ErrorTree<&str>> {
/// tag("hello")(s)
/// }
///
/// assert_matches!(
/// parse_hello("hello, world!"),
/// Ok((", world!", "hello")),
/// );
///
/// assert_matches!(
/// parse_hello("something"),
/// Err(Err::Error(ErrorTree::Base {
/// location: "something",
/// kind: BaseErrorKind::Expected(Expectation::Tag("hello")),
/// }))
/// );
///
/// assert_matches!(
/// parse_hello("hel"),
/// Err(Err::Incomplete(Needed::Size(n))) if n.get() == 2,
/// );
/// ```
pub fn tag<T, I, E>(tag: T) -> impl Clone + Fn(I) -> IResult<I, I, E>
where
T: InputLength + Clone,
I: InputLength + InputTake + Compare<T>,
E: TagError<I, T>,
{
let tag_len = tag.input_len();
move |input: I| match input.compare(tag.clone()) {
CompareResult::Ok => Ok(input.take_split(tag_len)),
CompareResult::Incomplete => {
Err(Err::Incomplete(Needed::new(tag_len - input.input_len())))
}
CompareResult::Error => Err(Err::Error(E::from_tag(input, tag.clone()))),
}
}
/// Parser recognizing a fixed pattern, called a tag. If the front of the
/// input data matches the `tag`, case insensitively, that part of the
/// input will be returned. Records the tag in the error in the event of a
/// parse failure via [`TagError`]. If there is only a partial match,
/// returns [`Err::Incomplete`][[nom::Err::Incomplete]].
///
/// # Example
///
/// ```
/// # use nom::{IResult, Err, Needed};
/// use cool_asserts::assert_matches;
/// use nom_supreme::tag::streaming::tag_no_case;
/// use nom_supreme::error::{ErrorTree, BaseErrorKind, Expectation};
///
/// fn parse_hello(s: &str) -> IResult<&str, &str, ErrorTree<&str>> {
/// tag_no_case("hello")(s)
/// }
///
/// assert_matches!(
/// parse_hello("HELLO, WORLD!"),
/// Ok((", WORLD!", "HELLO")),
/// );
///
/// assert_matches!(
/// parse_hello("something"),
/// Err(Err::Error(ErrorTree::Base {
/// location: "something",
/// kind: BaseErrorKind::Expected(Expectation::Tag("hello")),
/// }))
/// );
///
/// assert_matches!(
/// parse_hello("HEL"),
/// Err(Err::Incomplete(Needed::Size(n))) if n.get() == 2,
/// );
/// ```
pub fn tag_no_case<T, I, E>(tag: T) -> impl Clone + Fn(I) -> IResult<I, I, E>
where
T: InputLength + Clone,
I: InputLength + InputTake + Compare<T>,
E: TagError<I, T>,
{
let tag_len = tag.input_len();
move |input: I| match input.compare_no_case(tag.clone()) {
CompareResult::Ok => Ok(input.take_split(tag_len)),
CompareResult::Incomplete => {
Err(Err::Incomplete(Needed::new(tag_len - input.input_len())))
}
CompareResult::Error => Err(Err::Error(E::from_tag_no_case(input, tag.clone()))),
}
}
}