//! 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, HashSet};
use std::path::PathBuf;
use regex::Regex;
use crate::warnings::WarningKind;
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")]
pub mod impure;
pub mod versions;
/// Coerce a Nix Value to a plain path, e.g. in order to access the
/// file it points to via either `builtins.toPath` or an impure
/// builtin. This coercion can _never_ be performed in a Nix program
/// without using builtins (i.e. the trick `path: /. + path` to
/// convert from a string to a path wouldn't hit this code).
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("abort", &[true], |args: Vec<Value>, _: &mut VM| {
Err(ErrorKind::Abort(args[0].to_str()?.to_string()))
}),
Builtin::new(
"add",
&[false, false],
|args: Vec<Value>, vm: &mut VM| arithmetic_op!(&*args[0].force(vm)?, &*args[1].force(vm)?, +),
),
Builtin::new("all", &[true, true], |args: Vec<Value>, vm: &mut VM| {
for value in args[1].to_list()?.into_iter() {
let pred_result = vm.call_with(&args[0], [value])?;
if !pred_result.force(vm)?.as_bool()? {
return Ok(Value::Bool(false));
}
}
Ok(Value::Bool(true))
}),
Builtin::new("any", &[true, true], |args: Vec<Value>, vm: &mut VM| {
for value in args[1].to_list()?.into_iter() {
let pred_result = vm.call_with(&args[0], [value])?;
if pred_result.force(vm)?.as_bool()? {
return Ok(Value::Bool(true));
}
}
Ok(Value::Bool(false))
}),
Builtin::new("attrNames", &[true], |args: Vec<Value>, _: &mut VM| {
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: Vec<Value>, _: &mut VM| {
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("baseNameOf", &[true], |args: Vec<Value>, vm: &mut VM| {
let s = args[0].coerce_to_string(CoercionKind::Weak, vm)?;
let result: String = s.rsplit_once('/').map(|(_, x)| x).unwrap_or(&s).into();
Ok(result.into())
}),
Builtin::new("bitAnd", &[true, true], |args: Vec<Value>, _: &mut VM| {
Ok(Value::Integer(args[0].as_int()? & args[1].as_int()?))
}),
Builtin::new("bitOr", &[true, true], |args: Vec<Value>, _: &mut VM| {
Ok(Value::Integer(args[0].as_int()? | args[1].as_int()?))
}),
Builtin::new("bitXor", &[true, true], |args: Vec<Value>, _: &mut VM| {
Ok(Value::Integer(args[0].as_int()? ^ args[1].as_int()?))
}),
Builtin::new(
"catAttrs",
&[true, true],
|args: Vec<Value>, vm: &mut 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: Vec<Value>, _: &mut VM| {
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: Vec<Value>, vm: &mut 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(
"concatMap",
&[true, true],
|args: Vec<Value>, vm: &mut VM| {
let list = args[1].to_list()?;
let mut res = Vec::new();
for val in list {
res.extend(vm.call_with(&args[0], [val])?.force(vm)?.to_list()?);
}
Ok(Value::List(res.into()))
},
),
Builtin::new(
"concatStringsSep",
&[true, true],
|args: Vec<Value>, vm: &mut VM| {
let separator = args[0].to_str()?;
let list = args[1].to_list()?;
let mut res = String::new();
for (i, val) in list.into_iter().enumerate() {
if i != 0 {
res.push_str(&separator);
}
res.push_str(&val.force(vm)?.coerce_to_string(CoercionKind::Weak, vm)?);
}
Ok(res.into())
},
),
Builtin::new(
"deepSeq",
&[true, true],
|mut args: Vec<Value>, vm: &mut VM| {
let arg2 = args.pop().unwrap();
let arg1 = args.pop().unwrap();
arg1.deep_force(vm, &mut Default::default())?;
Ok(arg2)
},
),
Builtin::new(
"div",
&[false, false],
|args: Vec<Value>, vm: &mut VM| arithmetic_op!(&*args[0].force(vm)?, &*args[1].force(vm)?, /),
),
Builtin::new("dirOf", &[true], |args: Vec<Value>, vm: &mut VM| {
let s = args[0].coerce_to_string(CoercionKind::Weak, vm)?;
let result = s
.rsplit_once('/')
.map(|(x, _)| match x {
"" => "/",
_ => x,
})
.unwrap_or(".");
if args[0].is_path() {
Ok(Value::Path(result.into()))
} else {
Ok(result.into())
}
}),
Builtin::new("elem", &[true, true], |args: Vec<Value>, vm: &mut VM| {
for val in args[1].to_list()? {
if val.nix_eq(&args[0], vm)? {
return Ok(true.into());
}
}
Ok(false.into())
}),
Builtin::new("elemAt", &[true, true], |args: Vec<Value>, _: &mut VM| {
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: Vec<Value>, vm: &mut VM| {
let list: NixList = args[1].to_list()?;
list.into_iter()
.filter_map(|elem| {
let result = match vm.call_with(&args[0], [elem.clone()]) {
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(
"foldl'",
&[true, false, true],
|mut args: Vec<Value>, vm: &mut VM| {
let list = args.pop().unwrap().to_list()?;
let mut res = args.pop().unwrap();
let op = args.pop().unwrap();
for val in list {
res = vm.call_with(&op, [res, val])?;
res.force(vm)?;
}
Ok(res)
},
),
Builtin::new("functionArgs", &[true], |args: Vec<Value>, _: &mut VM| {
let lambda = args[0].to_closure()?.lambda();
let formals = if let Some(formals) = &lambda.formals {
formals
} else {
return Ok(Value::attrs(NixAttrs::empty()));
};
Ok(Value::attrs(NixAttrs::from_map(
formals
.arguments
.iter()
.map(|(k, v)| (k.clone(), (*v).into()))
.collect(),
)))
}),
Builtin::new("fromJSON", &[true], |args: Vec<Value>, _: &mut VM| {
let json_str = args[0].to_str()?;
let json: serde_json::Value = serde_json::from_str(&json_str)?;
json.try_into()
}),
Builtin::new("genList", &[true, true], |args: Vec<Value>, vm: &mut VM| {
let len = args[1].as_int()?;
(0..len)
.map(|i| vm.call_with(&args[0], [i.into()]))
.collect::<Result<Vec<Value>, _>>()
.map(|list| Value::List(NixList::from(list)))
.map_err(Into::into)
}),
Builtin::new("getAttr", &[true, true], |args: Vec<Value>, _: &mut VM| {
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("groupBy", &[true, true], |args: Vec<Value>, vm: &mut VM| {
let mut res: BTreeMap<NixString, Value> = BTreeMap::new();
for val in args[1].to_list()? {
let key = vm.call_with(&args[0], [val.clone()])?.force(vm)?.to_str()?;
res.entry(key)
.or_insert_with(|| Value::List(NixList::new()))
.as_list_mut()?
.push(val);
}
Ok(Value::attrs(NixAttrs::from_map(res)))
}),
Builtin::new("hasAttr", &[true, true], |args: Vec<Value>, _: &mut VM| {
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: Vec<Value>, _: &mut VM| {
match args[0].to_list()?.get(0) {
Some(x) => Ok(x.clone()),
None => Err(ErrorKind::IndexOutOfBounds { index: 0 }),
}
}),
Builtin::new(
"intersectAttrs",
&[true, true],
|args: Vec<Value>, _: &mut VM| {
let mut res = BTreeMap::new();
let attrs1 = args[0].to_attrs()?;
let attrs2 = args[1].to_attrs()?;
for (k, v) in attrs2.iter() {
if attrs1.contains(k) {
res.insert(k.clone(), v.clone());
}
}
Ok(Value::attrs(NixAttrs::from_map(res)))
},
),
// For `is*` predicates we force manually, as Value::force also unwraps any Thunks
Builtin::new("isAttrs", &[false], |args: Vec<Value>, vm: &mut VM| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::Attrs(_))))
}),
Builtin::new("isBool", &[false], |args: Vec<Value>, vm: &mut VM| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::Bool(_))))
}),
Builtin::new("isFloat", &[false], |args: Vec<Value>, vm: &mut VM| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::Float(_))))
}),
Builtin::new("isFunction", &[false], |args: Vec<Value>, vm: &mut VM| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(
*value,
Value::Closure(_) | Value::Builtin(_)
)))
}),
Builtin::new("isInt", &[false], |args: Vec<Value>, vm: &mut VM| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::Integer(_))))
}),
Builtin::new("isList", &[false], |args: Vec<Value>, vm: &mut VM| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::List(_))))
}),
Builtin::new("isNull", &[false], |args: Vec<Value>, vm: &mut VM| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::Null)))
}),
Builtin::new("isPath", &[false], |args: Vec<Value>, vm: &mut VM| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::Path(_))))
}),
Builtin::new("isString", &[false], |args: Vec<Value>, vm: &mut VM| {
let value = args[0].force(vm)?;
Ok(Value::Bool(matches!(*value, Value::String(_))))
}),
Builtin::new("length", &[true], |args: Vec<Value>, _: &mut VM| {
Ok(Value::Integer(args[0].to_list()?.len() as i64))
}),
Builtin::new(
"lessThan",
&[false, false],
|args: Vec<Value>, vm: &mut VM| cmp_op!(&*args[0].force(vm)?, &*args[1].force(vm)?, <),
),
Builtin::new("listToAttrs", &[true], |args: Vec<Value>, vm: &mut VM| {
let list = args[0].to_list()?;
let mut map = BTreeMap::new();
for val in list {
let attrs = val.force(vm)?.to_attrs()?;
let get = |key| {
attrs
.select(key)
.ok_or(ErrorKind::AttributeNotFound { name: key.into() })
};
let name = get("name")?.to_str()?;
let value = get("value")?.clone();
// Map entries earlier in the list take precedence over entries later in the list
map.entry(name).or_insert(value);
}
Ok(Value::attrs(NixAttrs::from_map(map)))
}),
Builtin::new("map", &[true, true], |args: Vec<Value>, vm: &mut VM| {
let list: NixList = args[1].to_list()?;
list.into_iter()
.map(|val| vm.call_with(&args[0], [val]))
.collect::<Result<Vec<Value>, _>>()
.map(|list| Value::List(NixList::from(list)))
.map_err(Into::into)
}),
Builtin::new(
"match",
&[true, true],
|mut args: Vec<Value>, _: &mut VM| {
let s = args.pop().unwrap().to_str()?;
let re = args.pop().unwrap().to_str()?;
let re: Regex = Regex::new(&format!("^{}$", re.as_str())).unwrap();
match re.captures(&s) {
Some(caps) => Ok(caps
.iter()
.skip(1)
.map(|grp| grp.map(|g| Value::from(g.as_str())).unwrap_or(Value::Null))
.collect::<Vec<Value>>()
.into()),
None => Ok(Value::Null),
}
},
),
Builtin::new(
"mul",
&[false, false],
|args: Vec<Value>, vm: &mut VM| arithmetic_op!(&*args[0].force(vm)?, &*args[1].force(vm)?, *),
),
Builtin::new("parseDrvName", &[true], |args: Vec<Value>, _vm: &mut VM| {
// This replicates cppnix's (mis?)handling of codepoints
// above U+007f following 0x2d ('-')
let s = args[0].to_str()?;
let slice: &[u8] = s.as_str().as_ref();
let (name, dash_and_version) = slice.split_at(
slice
.windows(2)
.enumerate()
.find_map(|x| match x {
(idx, [b'-', c1]) if !c1.is_ascii_alphabetic() => Some(idx),
_ => None,
})
.unwrap_or(slice.len()),
);
let version = dash_and_version
.split_first()
.map(|x| core::str::from_utf8(x.1))
.unwrap_or(Ok(""))?
.into();
Ok(Value::attrs(NixAttrs::from_map(BTreeMap::from([
(NixString::NAME, core::str::from_utf8(name)?.into()),
("version".into(), version),
]))))
}),
Builtin::new(
"partition",
&[true, true],
|args: Vec<Value>, vm: &mut VM| {
let mut right: Vec<Value> = vec![];
let mut wrong: Vec<Value> = vec![];
let list: NixList = args[1].to_list()?;
for elem in list.into_iter() {
let result = vm.call_with(&args[0], [elem.clone()])?;
if result.force(vm)?.as_bool()? {
right.push(elem);
} else {
wrong.push(elem);
};
}
let mut res: BTreeMap<NixString, Value> = BTreeMap::new();
res.insert("right".into(), Value::List(right.into()));
res.insert("wrong".into(), Value::List(wrong.into()));
Ok(Value::attrs(NixAttrs::from_map(res)))
},
),
Builtin::new(
"removeAttrs",
&[true, true],
|args: Vec<Value>, _: &mut VM| {
let attrs = args[0].to_attrs()?;
let keys = args[1]
.to_list()?
.into_iter()
.map(|v| v.to_str())
.collect::<Result<HashSet<_>, _>>()?;
let mut res = BTreeMap::new();
for (k, v) in attrs.iter() {
if !keys.contains(k) {
res.insert(k.clone(), v.clone());
}
}
Ok(Value::attrs(NixAttrs::from_map(res)))
},
),
Builtin::new("seq", &[true, true], |mut args: Vec<Value>, _: &mut VM| {
// The builtin calling infra has already forced both args for us, so we just return the
// second and ignore the first
Ok(args.pop().unwrap())
}),
Builtin::new("splitVersion", &[true], |args: Vec<Value>, _: &mut VM| {
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: Vec<Value>, vm: &mut 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: Vec<Value>, vm: &mut VM| arithmetic_op!(&*args[0].force(vm)?, &*args[1].force(vm)?, -),
),
Builtin::new(
"substring",
&[true, true, true],
|args: Vec<Value>, _: &mut VM| {
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: Vec<Value>, _: &mut VM| {
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: Vec<Value>, _: &mut VM| {
Err(ErrorKind::Throw(args[0].to_str()?.to_string()))
}),
// coerce_to_string forces for us
Builtin::new("toString", &[false], |args: Vec<Value>, vm: &mut VM| {
args[0]
.coerce_to_string(CoercionKind::Strong, vm)
.map(Value::String)
}),
Builtin::new(
"trace",
&[true, true],
|mut args: Vec<Value>, _: &mut VM| {
let value = args.pop().unwrap();
let trace_value = args.pop().unwrap();
// TODO(grfn): `trace` should be pluggable and capturable, probably via a method on
// the VM
println!("trace: {} :: {}", trace_value, trace_value.type_of());
Ok(value)
},
),
Builtin::new("tryEval", &[false], |args: Vec<Value>, vm: &mut VM| {
let mut res = BTreeMap::new();
match args[0].force(vm) {
Ok(value) => {
res.insert("value".into(), (*value).clone());
res.insert("success".into(), true.into());
}
Err(e) if e.is_catchable() => {
res.insert("value".into(), false.into());
res.insert("success".into(), false.into());
}
Err(e) => return Err(e),
}
Ok(Value::attrs(NixAttrs::from_map(res)))
}),
Builtin::new("toPath", &[false], |args: Vec<Value>, vm: &mut VM| {
let path: Value = crate::value::canon_path(coerce_value_to_path(&args[0], vm)?).into();
Ok(path.coerce_to_string(CoercionKind::Weak, vm)?.into())
}),
Builtin::new("typeOf", &[false], |args: Vec<Value>, vm: &mut 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()))
}),
]
}
/// Placeholder builtins that technically have a function which we do
/// not yet implement, but which is also not easily observable from
/// within a pure evaluation context.
///
/// These are used as a crutch to make progress on nixpkgs evaluation.
fn placeholders() -> Vec<Builtin> {
vec![Builtin::new(
"addErrorContext",
&[false, false],
|mut args: Vec<Value>, vm: &mut VM| {
vm.emit_warning(WarningKind::NotImplemented("builtins.addErrorContext"));
Ok(args.pop().unwrap())
},
)]
}
// we set TVIX_CURRENT_SYSTEM in build.rs
pub const CURRENT_PLATFORM: &str = env!("TVIX_CURRENT_SYSTEM");
fn builtins_set() -> NixAttrs {
let mut map: BTreeMap<NixString, Value> = BTreeMap::new();
// Pure-value builtins
map.insert(
"nixVersion".into(),
Value::String("2.3-compat-tvix-0.1".into()),
);
map.insert("langVersion".into(), Value::Integer(6));
map.insert(
"currentSystem".into(),
crate::systems::llvm_triple_to_nix_double(CURRENT_PLATFORM).into(),
);
let mut add_builtins = |builtins: Vec<Builtin>| {
for builtin in builtins {
map.insert(builtin.name().into(), Value::Builtin(builtin));
}
};
add_builtins(pure_builtins());
add_builtins(placeholders());
#[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(builtins));
globals
}
