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//! This module implements Nix language strings and their different
//! backing implementations.
use smol_str::SmolStr;
use std::hash::Hash;
use std::{borrow::Cow, fmt::Display, str::Chars};
#[derive(Clone, Debug)]
enum StringRepr {
Smol(SmolStr),
Heap(String),
}
#[repr(transparent)]
#[derive(Clone, Debug)]
pub struct NixString(StringRepr);
impl PartialEq for NixString {
fn eq(&self, other: &Self) -> bool {
self.as_str() == other.as_str()
}
}
impl Eq for NixString {}
impl PartialOrd for NixString {
fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
self.as_str().partial_cmp(other.as_str())
}
}
impl Ord for NixString {
fn cmp(&self, other: &Self) -> std::cmp::Ordering {
self.as_str().cmp(other.as_str())
}
}
impl From<&str> for NixString {
fn from(s: &str) -> Self {
NixString(StringRepr::Smol(SmolStr::new(s)))
}
}
impl From<String> for NixString {
fn from(s: String) -> Self {
NixString(StringRepr::Heap(s))
}
}
impl From<SmolStr> for NixString {
fn from(s: SmolStr) -> Self {
NixString(StringRepr::Smol(s))
}
}
impl Hash for NixString {
fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
self.as_str().hash(state)
}
}
#[cfg(feature = "arbitrary")]
mod arbitrary {
use super::*;
use proptest::prelude::{any_with, Arbitrary};
use proptest::prop_oneof;
use proptest::strategy::{BoxedStrategy, Strategy};
impl Arbitrary for NixString {
type Parameters = <String as Arbitrary>::Parameters;
type Strategy = BoxedStrategy<Self>;
fn arbitrary_with(args: Self::Parameters) -> Self::Strategy {
prop_oneof![
// Either generate `StringRepr::Heap`...
any_with::<String>(args).prop_map(Self::from),
// ...or generate `StringRepr::Smol` (which `impl From<&str> for NixString` returns)
any_with::<String>(args).prop_map(|s| Self::from(s.as_str())),
]
.boxed()
}
}
}
impl NixString {
pub const NAME: Self = NixString(StringRepr::Smol(SmolStr::new_inline("name")));
pub const NAME_REF: &'static Self = &Self::NAME;
pub const VALUE: Self = NixString(StringRepr::Smol(SmolStr::new_inline("value")));
pub const VALUE_REF: &'static Self = &Self::VALUE;
pub fn as_str(&self) -> &str {
match &self.0 {
StringRepr::Smol(s) => s.as_str(),
StringRepr::Heap(s) => s,
}
}
/// Return a displayable representation of the string as an
/// identifier.
///
/// This is used when printing out strings used as e.g. attribute
/// set keys, as those are only escaped in the presence of special
/// characters.
pub fn ident_str(&self) -> Cow<str> {
let escaped = nix_escape_string(self.as_str());
match escaped {
// A borrowed string is unchanged and can be returned as
// is.
Cow::Borrowed(_) => escaped,
// An owned string has escapes, and needs the outer quotes
// for display.
Cow::Owned(s) => Cow::Owned(format!("\"{}\"", s)),
}
}
pub fn concat(&self, other: &Self) -> Self {
let mut s = self.as_str().to_owned();
s.push_str(other.as_str());
NixString(StringRepr::Heap(s))
}
pub fn chars(&self) -> Chars<'_> {
match &self.0 {
StringRepr::Heap(h) => h.chars(),
StringRepr::Smol(s) => s.chars(),
}
}
}
fn nix_escape_char(ch: char, next: Option<&char>) -> Option<&'static str> {
match (ch, next) {
('\\', _) => Some("\\\\"),
('"', _) => Some("\\\""),
('\n', _) => Some("\\n"),
('\t', _) => Some("\\t"),
('\r', _) => Some("\\r"),
('$', Some('{')) => Some("\\$"),
_ => None,
}
}
/// Escape a Nix string for display, as most user-visible representation
/// are escaped strings.
///
/// Note that this does not add the outer pair of surrounding quotes.
fn nix_escape_string(input: &str) -> Cow<str> {
let mut iter = input.chars().enumerate().peekable();
while let Some((i, c)) = iter.next() {
if let Some(esc) = nix_escape_char(c, iter.peek().map(|(_, c)| c)) {
let mut escaped = String::with_capacity(input.len());
escaped.push_str(&input[..i]);
escaped.push_str(esc);
let mut inner_iter = input[i + 1..].chars().peekable();
while let Some(c) = inner_iter.next() {
match nix_escape_char(c, inner_iter.peek()) {
Some(esc) => escaped.push_str(esc),
None => escaped.push(c),
}
}
return Cow::Owned(escaped);
}
}
Cow::Borrowed(input)
}
impl Display for NixString {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.write_str("\"")?;
f.write_str(&nix_escape_string(self.as_str()))?;
f.write_str("\"")
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::properties::{eq_laws, hash_laws, ord_laws};
eq_laws!(NixString);
hash_laws!(NixString);
ord_laws!(NixString);
}
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