serde_cursor 0.4.0

fetch the desired parts of a serde-compatible data format efficiently using a jq-like language
Documentation 
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#[cfg(feature = "alloc")]
use alloc::collections::BTreeSet;
#[cfg(feature = "alloc")]
use alloc::collections::LinkedList;
#[cfg(feature = "alloc")]
use alloc::collections::VecDeque;
#[cfg(feature = "alloc")]
use alloc::string::String;
#[cfg(feature = "alloc")]
use alloc::vec::Vec;
#[cfg(feature = "std")]
use core::hash::Hash;
#[cfg(feature = "std")]
use std::collections::HashSet;

/// Sequences of items, such as [`Vec<T>`] or [`HashSet<T>`].
/// The index-all `[]` syntax requires this trait to be implemented.
///
/// The purpose of this trait is to enable the index-all `[]` syntax
/// when collecting fields of an array:
///
/// ```toml
/// [[package]]
/// serde = "1.0"
///
/// [[package]]
/// rand = "0.9"
/// ```
///
/// The index-all `[]` accesses every element in an array:
///
/// ```
/// # mod fs { pub fn read_to_string(_: &str) -> Result<String, Box<dyn std::error::Error>> { Ok(String::from("package = [{ name = 'serde' }, { name = 'rand' }]")) } }
/// use serde_cursor::Cursor;
///
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// let file = fs::read_to_string("Cargo.lock")?;
///
/// let packages: Vec<String> = toml::from_str::<Cursor!(package[].name)>(&file)?.0;
///
/// assert_eq!(packages, vec!["serde", "rand"]);
/// # Ok(()) }
/// ```
///
/// Instead of `packages: Vec<String>`, we could have used any of these types:
///
/// - [`HashSet<String>`]
/// - [`VecDeque<String>`]
/// - [`LinkedList<String>`]
pub trait Sequence: Default {
    type Item;

    fn push(&mut self, item: Self::Item);

    fn with_capacity(capacity: usize) -> Self {
        let _ = capacity;
        Self::default()
    }
}

#[cfg(feature = "alloc")]
impl<T> Sequence for Vec<T> {
    type Item = T;

    fn push(&mut self, item: Self::Item) {
        Vec::push(self, item);
    }

    fn with_capacity(capacity: usize) -> Self {
        Vec::with_capacity(capacity)
    }
}

#[cfg(feature = "alloc")]
impl<T> Sequence for VecDeque<T> {
    type Item = T;

    fn push(&mut self, item: Self::Item) {
        self.push_back(item);
    }

    fn with_capacity(capacity: usize) -> Self {
        VecDeque::<T>::with_capacity(capacity)
    }
}

#[cfg(feature = "alloc")]
impl<T> Sequence for LinkedList<T> {
    type Item = T;

    fn push(&mut self, item: Self::Item) {
        self.push_back(item);
    }
}

#[cfg(feature = "std")]
impl<T, H> Sequence for HashSet<T, H>
where
    T: Eq + Hash,
    H: Default + core::hash::BuildHasher,
{
    type Item = T;

    fn push(&mut self, item: Self::Item) {
        self.insert(item);
    }

    fn with_capacity(capacity: usize) -> Self {
        HashSet::with_capacity_and_hasher(capacity, H::default())
    }
}

#[cfg(feature = "alloc")]
impl<T> Sequence for BTreeSet<T>
where
    T: Ord,
{
    type Item = T;

    fn push(&mut self, item: Self::Item) {
        self.insert(item);
    }
}

#[cfg(feature = "alloc")]
impl Sequence for String {
    type Item = char;

    fn push(&mut self, item: Self::Item) {
        self.push(item);
    }

    fn with_capacity(capacity: usize) -> Self {
        String::with_capacity(capacity)
    }
}

impl<T> Sequence for Option<T> {
    type Item = T;

    fn push(&mut self, item: Self::Item) {
        *self = Some(item);
    }
}