//! This module implements the builtins exposed in the Nix language.
//!
//! See //tvix/eval/docs/builtins.md for a some context on the
//! available builtins in Nix.
use std::{
cmp,
collections::{BTreeMap, HashMap},
path::PathBuf,
rc::Rc,
};
use crate::{
errors::ErrorKind,
value::{Builtin, CoercionKind, NixAttrs, NixList, NixString, Value},
vm::VM,
};
use crate::arithmetic_op;
use self::versions::VersionPartsIter;
pub mod versions;
/// Coerce a Nix Value to a plain path, e.g. in order to access the file it
/// points to in an I/O builtin. This coercion can _never_ be performed in
/// a Nix program directly (i.e. the trick `path: /. + path` to convert from
/// a string to a path wouldn't hit this code), so the target file
/// doesn't need to be realised or imported into the Nix store.
pub fn coerce_value_to_path(v: &Value, vm: &mut VM) -> Result<PathBuf, ErrorKind> {
let value = v.force(vm)?;
match &*value {
Value::Thunk(t) => coerce_value_to_path(&t.value(), vm),
Value::Path(p) => Ok(p.clone()),
_ => value
.coerce_to_string(CoercionKind::Weak, vm)
.map(|s| PathBuf::from(s.as_str()))
.and_then(|path| {
if path.is_absolute() {
Ok(path)
} else {
Err(ErrorKind::NotAnAbsolutePath(path))
}
}),
}
}
/// Return all pure builtins, that is all builtins that do not rely on
/// I/O outside of the VM and which can be used in any contexts (e.g.
/// WASM).
fn pure_builtins() -> Vec<Builtin> {
vec![
Builtin::new("add", &[true, true], |mut args, _| {
let b = args.pop().unwrap();
let a = args.pop().unwrap();
arithmetic_op!(a, b, +)
}),
Builtin::new("abort", &[true], |mut args, _| {
return Err(ErrorKind::Abort(
args.pop().unwrap().to_str()?.as_str().to_owned(),
));
}),
Builtin::new("attrNames", &[true], |args, _| {
let xs = args[0].to_attrs()?;
let mut output = Vec::with_capacity(xs.len());
for (key, _val) in xs.iter() {
output.push(Value::String(key.clone()));
}
Ok(Value::List(NixList::construct(output.len(), output)))
}),
Builtin::new("attrValues", &[true], |args, _| {
let xs = args[0].to_attrs()?;
let mut output = Vec::with_capacity(xs.len());
for (_key, val) in xs.iter() {
output.push(val.clone());
}
Ok(Value::List(NixList::construct(output.len(), output)))
}),
Builtin::new("bitAnd", &[true, true], |args, _| {
Ok(Value::Integer(args[0].as_int()? & args[1].as_int()?))
}),
Builtin::new("bitOr", &[true, true], |args, _| {
Ok(Value::Integer(args[0].as_int()? | args[1].as_int()?))
}),
Builtin::new("bitXor", &[true, true], |args, _| {
Ok(Value::Integer(args[0].as_int()? ^ args[1].as_int()?))
}),
Builtin::new("catAttrs", &[true, true], |mut args, _| {
let list = args.pop().unwrap().to_list()?;
let key = args.pop().unwrap().to_str()?;
let mut output = vec![];
for set in list.into_iter() {
if let Some(value) = set.to_attrs()?.select(key.as_str()) {
output.push(value.clone());
}
}
Ok(Value::List(NixList::construct(output.len(), output)))
}),
Builtin::new("compareVersions", &[true, true], |args, _| {
let s1 = args[0].to_str()?;
let s1 = VersionPartsIter::new(s1.as_str());
let s2 = args[1].to_str()?;
let s2 = VersionPartsIter::new(s2.as_str());
match s1.cmp(s2) {
std::cmp::Ordering::Less => Ok(Value::Integer(-1)),
std::cmp::Ordering::Equal => Ok(Value::Integer(0)),
std::cmp::Ordering::Greater => Ok(Value::Integer(1)),
}
}),
Builtin::new("div", &[true, true], |mut args, _| {
let b = args.pop().unwrap();
let a = args.pop().unwrap();
arithmetic_op!(a, b, /)
}),
Builtin::new("elemAt", &[true, true], |args, _| {
let xs = args[0].to_list()?;
let i = args[1].as_int()?;
if i < 0 {
Err(ErrorKind::IndexOutOfBounds { index: i })
} else {
match xs.get(i as usize) {
Some(x) => Ok(x.clone()),
None => Err(ErrorKind::IndexOutOfBounds { index: i }),
}
}
}),
Builtin::new("length", &[true], |args, _| {
Ok(Value::Integer(args[0].to_list()?.len() as i64))
}),
Builtin::new("head", &[true], |args, _| match args[0].to_list()?.get(0) {
Some(x) => Ok(x.clone()),
None => Err(ErrorKind::IndexOutOfBounds { index: 0 }),
}),
Builtin::new("isAttrs", &[true], |args, _| {
Ok(Value::Bool(matches!(args[0], Value::Attrs(_))))
}),
Builtin::new("isBool", &[true], |args, _| {
Ok(Value::Bool(matches!(args[0], Value::Bool(_))))
}),
Builtin::new("isFloat", &[true], |args, _| {
Ok(Value::Bool(matches!(args[0], Value::Float(_))))
}),
Builtin::new("isFunction", &[true], |args, _| {
Ok(Value::Bool(matches!(
args[0],
Value::Closure(_) | Value::Builtin(_)
)))
}),
Builtin::new("isInt", &[true], |args, _| {
Ok(Value::Bool(matches!(args[0], Value::Integer(_))))
}),
Builtin::new("isList", &[true], |args, _| {
Ok(Value::Bool(matches!(args[0], Value::List(_))))
}),
Builtin::new("isNull", &[true], |args, _| {
Ok(Value::Bool(matches!(args[0], Value::Null)))
}),
Builtin::new("isPath", &[true], |args, _| {
Ok(Value::Bool(matches!(args[0], Value::Path(_))))
}),
Builtin::new("isString", &[true], |args, _| {
Ok(Value::Bool(matches!(args[0], Value::String(_))))
}),
Builtin::new("mul", &[true, true], |mut args, _| {
let b = args.pop().unwrap();
let a = args.pop().unwrap();
arithmetic_op!(a, b, *)
}),
Builtin::new("sub", &[true, true], |mut args, _| {
let b = args.pop().unwrap();
let a = args.pop().unwrap();
arithmetic_op!(a, b, -)
}),
Builtin::new("substring", &[true, true, true], |args, _| {
let beg = args[0].as_int()?;
let len = args[1].as_int()?;
let x = args[2].to_str()?;
if beg < 0 {
return Err(ErrorKind::IndexOutOfBounds { index: beg });
}
let beg = beg as usize;
// Nix doesn't assert that the length argument is
// non-negative when the starting index is GTE the
// string's length.
if beg >= x.as_str().len() {
return Ok(Value::String("".into()));
}
if len < 0 {
return Err(ErrorKind::NegativeLength { length: len });
}
let len = len as usize;
let end = cmp::min(beg + len, x.as_str().len());
Ok(Value::String(
x.as_str()[(beg as usize)..(end as usize)].into(),
))
}),
Builtin::new("tail", &[true], |args, _| {
let xs = args[0].to_list()?;
if xs.len() == 0 {
Err(ErrorKind::TailEmptyList)
} else {
let output = xs.into_iter().skip(1).collect::<Vec<_>>();
Ok(Value::List(NixList::construct(output.len(), output)))
}
}),
Builtin::new("throw", &[true], |mut args, _| {
return Err(ErrorKind::Throw(
args.pop().unwrap().to_str()?.as_str().to_owned(),
));
}),
Builtin::new("toString", &[true], |args, vm| {
args[0]
.coerce_to_string(CoercionKind::Strong, vm)
.map(Value::String)
}),
Builtin::new("typeOf", &[false], |args, vm| {
// We force manually here because it also unwraps the Thunk
// representation, if any.
// TODO(sterni): it'd be nice if we didn't have to worry about this
let value = args[0].force(vm)?;
Ok(Value::String(value.type_of().into()))
}),
]
}
fn builtins_set() -> NixAttrs {
let mut map: BTreeMap<NixString, Value> = BTreeMap::new();
for builtin in pure_builtins() {
map.insert(builtin.name().into(), Value::Builtin(builtin));
}
NixAttrs::from_map(map)
}
/// Set of Nix builtins that are globally available.
pub fn global_builtins() -> HashMap<&'static str, Value> {
let builtins = builtins_set();
let mut globals: HashMap<&'static str, Value> = HashMap::new();
// known global builtins from the builtins set.
for global in &[
"abort",
"baseNameOf",
"derivation",
"derivationStrict",
"dirOf",
"fetchGit",
"fetchMercurial",
"fetchTarball",
"fromTOML",
"import",
"isNull",
"map",
"placeholder",
"removeAttrs",
"scopedImport",
"throw",
"toString",
] {
if let Some(builtin) = builtins.select(global) {
globals.insert(global, builtin.clone());
}
}
globals.insert("builtins", Value::Attrs(Rc::new(builtins)));
globals
}
