Struct NonEmptyVec 

pub struct NonEmptyVec<T> {
    pub head: T,
    pub tail: Vec<T>,
}

A vector guaranteed to contain at least one element.

Follows the “Parse, don’t validate” pattern: the non-empty invariant is established once via NonEmptyVec::from_vec or TryFrom<Vec<T>>, and NonEmptyVec::first is then infallible (returns &T, not Option<&T>).

The shape mirrors the nonempty crate discussed in Eli Bendersky’s “Rusty thoughts on Parse, don’t validate”: head holds the first element, tail holds the rest, so no indexing or unwrap is needed downstream.

use vtcode_commons::validation::NonEmptyVec;

let parsed = NonEmptyVec::from_vec(vec!["a", "b"]).expect("non-empty");
assert_eq!(parsed.first(), &"a");
assert!(NonEmptyVec::<String>::from_vec(Vec::new()).is_none());

Fields

head: T

First element; always present.

tail: Vec<T>

Remaining elements; possibly empty.

Implementations

impl<T> NonEmptyVec<T>

pub const fn new(head: T) -> Self

Create a singleton collection from one element.

pub const fn singleton(head: T) -> Self

Alias for NonEmptyVec::new, matching the nonempty crate naming.

pub fn from_vec(vec: Vec<T>) -> Option<Self>

Parse a Vec into a non-empty collection, returning None when empty.

This is the single boundary where the invariant is established. Order is preserved: head is the original vec[0].

pub const fn first(&self) -> &T

Infallible access to the first element; no Option to re-check.

pub fn last(&self) -> &T

Access the last element.

pub fn len(&self) -> usize

Number of elements; always >= 1.

pub const fn is_empty(&self) -> bool

Always returns false; provided for generic len/is_empty pairing.

pub fn iter(&self) -> impl Iterator<Item = &T>

Iterate over all elements in order.

pub fn push(&mut self, value: T)

Append an element to the end.

pub fn into_vec(self) -> Vec<T>

Consume into a plain Vec, preserving order.

Trait Implementations

impl<T: Clone> Clone for NonEmptyVec<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for NonEmptyVec<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de, T> Deserialize<'de> for NonEmptyVec<T>

where T: Deserialize<'de>,

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<T: Eq> Eq for NonEmptyVec<T>

impl<T> From<NonEmptyVec<T>> for Vec<T>

fn from(value: NonEmptyVec<T>) -> Self

Converts to this type from the input type.

impl<T: PartialEq> PartialEq for NonEmptyVec<T>

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl<T: Serialize> Serialize for NonEmptyVec<T>

fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl<T: PartialEq> StructuralPartialEq for NonEmptyVec<T>

impl<T> TryFrom<Vec<T>> for NonEmptyVec<T>

type Error = EmptyCollectionError

The type returned in the event of a conversion error.

fn try_from(value: Vec<T>) -> Result<Self, Self::Error>

Performs the conversion.