//! This module implements Nix language strings.
//!
//! Nix language strings never need to be modified on the language
//! level, allowing us to shave off some memory overhead and only
//! paying the cost when creating new strings.
use rnix::ast;
use std::collections::HashSet;
use std::ffi::OsStr;
use std::hash::Hash;
use std::ops::Deref;
use std::path::Path;
use std::str::{self, Utf8Error};
use std::{borrow::Cow, fmt::Display, str::Chars};
use serde::de::{Deserializer, Visitor};
use serde::{Deserialize, Serialize};
#[derive(Clone, Debug, Serialize, Hash, PartialEq, Eq)]
pub enum NixContextElement {
/// A plain store path (e.g. source files copied to the store)
Plain(String),
/// Single output of a derivation, represented by its name and its derivation path.
Single { name: String, derivation: String },
/// A reference to a complete derivation
/// including its source and its binary closure.
/// It is used for the `drvPath` attribute context.
/// The referred string is the store path to
/// the derivation path.
Derivation(String),
}
/// Nix context strings representation in Tvix. This tracks a set of different kinds of string
/// dependencies that we can come across during manipulation of our language primitives, mostly
/// strings. There's some simple algebra of context strings and how they propagate w.r.t. primitive
/// operations, e.g. concatenation, interpolation and other string operations.
#[repr(transparent)]
#[derive(Clone, Debug, Serialize, Default)]
pub struct NixContext(HashSet<NixContextElement>);
impl From<NixContextElement> for NixContext {
fn from(value: NixContextElement) -> Self {
Self([value].into())
}
}
impl NixContext {
/// Creates an empty context that can be populated
/// and passed to form a contextful [NixString], albeit
/// if the context is concretly empty, the resulting [NixString]
/// will be contextless.
pub fn new() -> Self {
Self::default()
}
/// For internal consumers, we let people observe
/// if the [NixContext] is actually empty or not
/// to decide whether they want to skip the allocation
/// of a full blown [HashSet].
pub(crate) fn is_empty(&self) -> bool {
self.0.is_empty()
}
/// Consumes a new [NixContextElement] and add it if not already
/// present in this context.
pub fn append(mut self, other: NixContextElement) -> Self {
self.0.insert(other);
self
}
/// Consumes both ends of the join into a new NixContent
/// containing the union of elements of both ends.
pub fn join(mut self, other: &mut NixContext) -> Self {
let other_set = std::mem::take(&mut other.0);
let mut set: HashSet<NixContextElement> = std::mem::take(&mut self.0);
set.extend(other_set);
Self(set)
}
/// Copies from another [NixString] its context strings
/// in this context.
pub fn mimic(&mut self, other: &NixString) {
if let Some(ref context) = other.1 {
self.0.extend(context.iter().cloned());
}
}
/// Iterates over "plain" context elements, e.g. sources imported
/// in the store without more information, i.e. `toFile` or coerced imported paths.
/// It yields paths to the store.
pub fn iter_plain(&self) -> impl Iterator<Item = &str> {
self.iter().filter_map(|elt| {
if let NixContextElement::Plain(s) = elt {
Some(s.as_str())
} else {
None
}
})
}
/// Iterates over "full derivations" context elements, e.g. something
/// referring to their `drvPath`, i.e. their full sources and binary closure.
/// It yields derivation paths.
pub fn iter_derivation(&self) -> impl Iterator<Item = &str> {
self.iter().filter_map(|elt| {
if let NixContextElement::Derivation(s) = elt {
Some(s.as_str())
} else {
None
}
})
}
/// Iterates over "single" context elements, e.g. single derived paths,
/// or also known as the single output of a given derivation.
/// The first element of the tuple is the output name
/// and the second element is the derivation path.
pub fn iter_single_outputs(&self) -> impl Iterator<Item = (&str, &str)> {
self.iter().filter_map(|elt| {
if let NixContextElement::Single { name, derivation } = elt {
Some((name.as_str(), derivation.as_str()))
} else {
None
}
})
}
/// Iterates over any element of the context.
pub fn iter(&self) -> impl Iterator<Item = &NixContextElement> {
self.0.iter()
}
/// Produces a list of owned references to this current context,
/// no matter its type.
pub fn to_owned_references(self) -> Vec<String> {
self.0
.into_iter()
.map(|ctx| match ctx {
NixContextElement::Derivation(drv_path) => drv_path,
NixContextElement::Plain(store_path) => store_path,
NixContextElement::Single { derivation, .. } => derivation,
})
.collect()
}
}
// FIXME: when serializing, ignore the context?
#[derive(Clone, Debug, Serialize)]
pub struct NixString(Box<str>, Option<NixContext>);
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> {
Some(self.cmp(other))
}
}
impl Ord for NixString {
fn cmp(&self, other: &Self) -> std::cmp::Ordering {
self.as_str().cmp(other.as_str())
}
}
impl TryFrom<&[u8]> for NixString {
type Error = Utf8Error;
fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
Ok(Self(Box::from(str::from_utf8(value)?), None))
}
}
impl From<&str> for NixString {
fn from(s: &str) -> Self {
NixString(Box::from(s), None)
}
}
impl From<String> for NixString {
fn from(s: String) -> Self {
NixString(s.into_boxed_str(), None)
}
}
impl From<(String, Option<NixContext>)> for NixString {
fn from(s: (String, Option<NixContext>)) -> Self {
NixString(s.0.into_boxed_str(), s.1)
}
}
impl From<Box<str>> for NixString {
fn from(s: Box<str>) -> Self {
Self(s, None)
}
}
impl From<ast::Ident> for NixString {
fn from(ident: ast::Ident) -> Self {
ident.ident_token().unwrap().text().into()
}
}
impl Hash for NixString {
fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
self.as_str().hash(state)
}
}
impl<'de> Deserialize<'de> for NixString {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
struct StringVisitor;
impl<'de> Visitor<'de> for StringVisitor {
type Value = NixString;
fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
formatter.write_str("a valid Nix string")
}
fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
Ok(v.into())
}
fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
Ok(v.into())
}
}
deserializer.deserialize_string(StringVisitor)
}
}
#[cfg(feature = "arbitrary")]
mod arbitrary {
use super::*;
use proptest::prelude::{any_with, Arbitrary};
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 {
any_with::<String>(args).prop_map(Self::from).boxed()
}
}
}
impl NixString {
pub fn new_inherit_context_from(other: &NixString, new_contents: &str) -> Self {
Self(Box::from(new_contents), other.1.clone())
}
pub fn new_context_from(context: NixContext, contents: &str) -> Self {
Self(
Box::from(contents),
if context.is_empty() {
None
} else {
Some(context)
},
)
}
pub fn as_str(&self) -> &str {
&self.0
}
/// 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(_) => {
if is_valid_nix_identifier(&escaped) && !is_keyword(&escaped) {
escaped
} else {
Cow::Owned(format!("\"{}\"", 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());
let context = [&self.1, &other.1]
.into_iter()
.flatten()
.fold(NixContext::new(), |acc_ctx, new_ctx| {
acc_ctx.join(&mut new_ctx.clone())
});
Self::new_context_from(context, &s.into_boxed_str())
}
pub fn iter_plain(&self) -> impl Iterator<Item = &str> {
return self.1.iter().flat_map(|context| context.iter_plain());
}
pub fn iter_derivation(&self) -> impl Iterator<Item = &str> {
return self.1.iter().flat_map(|context| context.iter_derivation());
}
pub fn iter_single_outputs(&self) -> impl Iterator<Item = (&str, &str)> {
return self
.1
.iter()
.flat_map(|context| context.iter_single_outputs());
}
/// Returns whether this Nix string possess a context or not.
pub fn has_context(&self) -> bool {
self.1.is_some()
}
/// This clears the context of that string, losing
/// all dependency tracking information.
pub fn clear_context(&mut self) {
self.1 = None;
}
pub fn chars(&self) -> Chars<'_> {
self.0.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,
}
}
/// Return true if this string is a keyword -- character strings
/// which lexically match the "identifier" production but are not
/// parsed as identifiers. See also cppnix commit
/// b72bc4a972fe568744d98b89d63adcd504cb586c.
fn is_keyword(s: &str) -> bool {
matches!(
s,
"if" | "then" | "else" | "assert" | "with" | "let" | "in" | "rec" | "inherit"
)
}
/// Return true if this string can be used as an identifier in Nix.
fn is_valid_nix_identifier(s: &str) -> bool {
// adapted from rnix-parser's tokenizer.rs
let mut chars = s.chars();
match chars.next() {
Some('a'..='z' | 'A'..='Z' | '_') => (),
_ => return false,
}
for c in chars {
match c {
'a'..='z' | 'A'..='Z' | '0'..='9' | '_' | '-' | '\'' => (),
_ => return false,
}
}
true
}
/// 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.char_indices().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);
// In theory we calculate how many bytes it takes to represent `esc`
// in UTF-8 and use that for the offset. It is, however, safe to
// assume that to be 1, as all characters that can be escaped in a
// Nix string are ASCII.
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("\"")
}
}
impl AsRef<str> for NixString {
fn as_ref(&self) -> &str {
self.as_str()
}
}
impl AsRef<OsStr> for NixString {
fn as_ref(&self) -> &OsStr {
self.as_str().as_ref()
}
}
impl AsRef<Path> for NixString {
fn as_ref(&self) -> &Path {
self.as_str().as_ref()
}
}
impl Deref for NixString {
type Target = str;
fn deref(&self) -> &Self::Target {
self.as_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);
}
