//! 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;
use std::collections::{BTreeMap, HashMap};
use std::path::PathBuf;
use std::rc::Rc;
use crate::{
errors::ErrorKind,
value::{Builtin, CoercionKind, NixAttrs, NixList, NixString, Value},
vm::VM,
};
use crate::{arithmetic_op, cmp_op};
use self::versions::{VersionPart, VersionPartsIter};
#[cfg(feature = "impure")]
mod impure;
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.
#[allow(dead_code)] // TODO(sterni): remove this once the function is in use
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",
&[false, false],
|args, vm| arithmetic_op!(&*args[0].force(vm)?, &*args[1].force(vm)?, +),
),
Builtin::new("abort", &[true], |args, _| {
Err(ErrorKind::Abort(args[0].to_str()?.to_string()))
}),
Builtin::new("all", &[true, true], |args, vm| {
for value in args[1].to_list()?.into_iter() {
let pred_result = {
vm.push(value);
vm.call_value(&args[0])
}?;
if !pred_result.force(vm)?.as_bool()? {
return Ok(Value::Bool(false));
}
}
Ok(Value::Bool(true))
}),
Builtin::new("any", &[true, true], |args, vm| {
for value in args[1].to_list()?.into_iter() {
let pred_result = {
vm.push(value);
vm.call_value(&args[0])
}?;
if pred_result.force(vm)?.as_bool()? {
return Ok(Value::Bool(true));
}
}
Ok(Value::Bool(false))
}),
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], |args, vm| {
let key = args[0].to_str()?;
let list = args[1].to_list()?;
let mut output = vec![];
for item in list.into_iter() {
let set = item.force(vm)?.to_attrs()?;
if let Some(value) = set.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_for_cmp(s1.as_str());
let s2 = args[1].to_str()?;
let s2 = VersionPartsIter::new_for_cmp(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("concatLists", &[true], |args, vm| {
let list = args[0].to_list()?;
let lists = list
.into_iter()
.map(|elem| {
let value = elem.force(vm)?;
value.to_list()
})
.collect::<Result<Vec<NixList>, ErrorKind>>()?;
Ok(Value::List(NixList::from(
lists.into_iter().flatten().collect::<Vec<Value>>(),
)))
}),
Builtin::new(
"div",
&[false, false],
|args, vm| arithmetic_op!(&*args[0].force(vm)?, &*args[1].force(vm)?, /),
),
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("filter", &[true, true], |args, vm| {
let list: NixList = args[1].to_list()?;
list.into_iter()
.filter_map(|elem| {
vm.push(elem.clone());
let result = match vm.call_value(&args[0]) {
Err(err) => return Some(Err(err)),
Ok(result) => result,
};
// Must be assigned to a local to avoid a borrowcheck
// failure related to the ForceResult destructor.
let result = match result.force(vm) {
Err(err) => Some(Err(vm.error(err))),
Ok(value) => match value.as_bool() {
Ok(true) => Some(Ok(elem)),
Ok(false) => None,
Err(err) => Some(Err(vm.error(err))),
},
};
result
})
.collect::<Result<Vec<Value>, _>>()
.map(|list| Value::List(NixList::from(list)))
.map_err(Into::into)
}),
Builtin::new("getAttr", &[true, true], |args, _| {
let k = args[0].to_str()?;
let xs = args[1].to_attrs()?;
match xs.select(k.as_str()) {
Some(x) => Ok(x.clone()),
None => Err(ErrorKind::AttributeNotFound {
name: k.to_string(),
}),
}
}),
Builtin::new("length", &[true], |args, _| {
Ok(Value::Integer(args[0].to_list()?.len() as i64))
}),
Builtin::new("map", &[true, true], |args, vm| {
let list: NixList = args[1].to_list()?;
list.into_iter()
.map(|val| {
// Leave the argument on the stack before calling the
// function.
vm.push(val);
vm.call_value(&args[0])
})
.collect::<Result<Vec<Value>, _>>()
.map(|list| Value::List(NixList::from(list)))
.map_err(Into::into)
}),
Builtin::new(
"lessThan",
&[false, false],
|args, vm| cmp_op!(&*args[0].force(vm)?, &*args[1].force(vm)?, <),
),
Builtin::new("hasAttr", &[true, true], |args, _| {
let k = args[0].to_str()?;
let xs = args[1].to_attrs()?;
Ok(Value::Bool(xs.contains(k.as_str())))
}),
Builtin::new("head", &[true], |args, _| match args[0].to_list()?.get(0) {
Some(x) => Ok(x.clone()),
None => Err(ErrorKind::IndexOutOfBounds { index: 0 }),
}),
// For `is*` predicates we force manually, as Value::force also unwraps any Thunks
Builtin::new("isAttrs", &[false], |args, vm| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::Attrs(_))))
}),
Builtin::new("isBool", &[false], |args, vm| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::Bool(_))))
}),
Builtin::new("isFloat", &[false], |args, vm| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::Float(_))))
}),
Builtin::new("isFunction", &[false], |args, vm| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(
*value,
Value::Closure(_) | Value::Builtin(_)
)))
}),
Builtin::new("isInt", &[false], |args, vm| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::Integer(_))))
}),
Builtin::new("isList", &[false], |args, vm| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::List(_))))
}),
Builtin::new("isNull", &[false], |args, vm| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::Null)))
}),
Builtin::new("isPath", &[false], |args, vm| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::Path(_))))
}),
Builtin::new("isString", &[false], |args, vm| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::String(_))))
}),
Builtin::new(
"mul",
&[false, false],
|args, vm| arithmetic_op!(&*args[0].force(vm)?, &*args[1].force(vm)?, *),
),
Builtin::new("splitVersion", &[true], |args, _| {
let s = args[0].to_str()?;
let s = VersionPartsIter::new(s.as_str());
let parts = s
.map(|s| {
Value::String(match s {
VersionPart::Number(n) => n.into(),
VersionPart::Word(w) => w.into(),
})
})
.collect::<Vec<Value>>();
Ok(Value::List(NixList::construct(parts.len(), parts)))
}),
Builtin::new("stringLength", &[false], |args, vm| {
// also forces the value
let s = args[0].coerce_to_string(CoercionKind::Weak, vm)?;
Ok(Value::Integer(s.as_str().len() as i64))
}),
Builtin::new(
"sub",
&[false, false],
|args, vm| arithmetic_op!(&*args[0].force(vm)?, &*args[1].force(vm)?, -),
),
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], |args, _| {
Err(ErrorKind::Throw(args[0].to_str()?.to_string()))
}),
// coerce_to_string forces for us
Builtin::new("toString", &[false], |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();
let mut add_builtins = |builtins: Vec<Builtin>| {
for builtin in builtins {
map.insert(builtin.name().into(), Value::Builtin(builtin));
}
};
add_builtins(pure_builtins());
#[cfg(feature = "impure")]
{
map.extend(impure::builtins());
}
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
}
