//! This module contains glue code translating from
//! [nix_compat::derivation::Derivation] to [tvix_build::buildservice::BuildRequest].
use std::collections::{BTreeMap, HashSet};
use std::path::PathBuf;
use bytes::Bytes;
use nix_compat::{derivation::Derivation, nixbase32, store_path::StorePath};
use sha2::{Digest, Sha256};
use tvix_build::buildservice::{AdditionalFile, BuildConstraints, BuildRequest, EnvVar};
use tvix_castore::Node;
/// These are the environment variables that Nix sets in its sandbox for every
/// build.
const NIX_ENVIRONMENT_VARS: [(&str, &str); 12] = [
("HOME", "/homeless-shelter"),
("NIX_BUILD_CORES", "0"), // TODO: make this configurable?
("NIX_BUILD_TOP", "/"),
("NIX_LOG_FD", "2"),
("NIX_STORE", "/nix/store"),
("PATH", "/path-not-set"),
("PWD", "/build"),
("TEMP", "/build"),
("TEMPDIR", "/build"),
("TERM", "xterm-256color"),
("TMP", "/build"),
("TMPDIR", "/build"),
];
/// Get an iterator of store paths whose nixbase32 hashes will be the needles for refscanning
/// Importantly, the returned order will match the one used by [derivation_to_build_request]
/// so users may use this function to map back from the found needles to a store path
pub(crate) fn get_refscan_needles(
derivation: &Derivation,
) -> impl Iterator<Item = &StorePath<String>> {
derivation
.outputs
.values()
.filter_map(|output| output.path.as_ref())
.chain(derivation.input_sources.iter())
.chain(derivation.input_derivations.keys())
}
/// Takes a [Derivation] and turns it into a [buildservice::BuildRequest].
/// It assumes the Derivation has been validated.
/// It needs two lookup functions:
/// - one translating input sources to a castore node
/// (`fn_input_sources_to_node`)
/// - one translating a tuple of drv path and (a subset of their) output names to
/// castore nodes of the selected outpus (`fn_input_drvs_to_output_nodes`).
pub(crate) fn derivation_to_build_request(
derivation: &Derivation,
inputs: BTreeMap<StorePath<String>, Node>,
) -> std::io::Result<BuildRequest> {
debug_assert!(derivation.validate(true).is_ok(), "drv must validate");
// produce command_args, which is builder and arguments in a Vec.
let mut command_args: Vec<String> = Vec::with_capacity(derivation.arguments.len() + 1);
command_args.push(derivation.builder.clone());
command_args.extend_from_slice(&derivation.arguments);
// Produce environment_vars and additional files.
// We use a BTreeMap while producing, and only realize the resulting Vec
// while populating BuildRequest, so we don't need to worry about ordering.
let mut environment_vars: BTreeMap<String, Bytes> = BTreeMap::new();
let mut additional_files: BTreeMap<String, Bytes> = BTreeMap::new();
// Start with some the ones that nix magically sets:
environment_vars.extend(
NIX_ENVIRONMENT_VARS
.iter()
.map(|(k, v)| (k.to_string(), Bytes::from_static(v.as_bytes()))),
);
// extend / overwrite with the keys set in the derivation environment itself.
// TODO: check if this order is correct, and environment vars set in the
// *Derivation actually* have priority.
environment_vars.extend(
derivation
.environment
.iter()
.map(|(k, v)| (k.clone(), Bytes::from(v.to_vec()))),
);
handle_pass_as_file(&mut environment_vars, &mut additional_files)?;
// TODO: handle __json (structured attrs, provide JSON file and source-able bash script)
// Produce constraints.
let mut constraints = HashSet::from([
BuildConstraints::System(derivation.system.clone()),
BuildConstraints::ProvideBinSh,
]);
if derivation.outputs.len() == 1
&& derivation
.outputs
.get("out")
.expect("Tvix bug: Derivation has no out output")
.is_fixed()
{
constraints.insert(BuildConstraints::NetworkAccess);
}
Ok(BuildRequest {
// Importantly, this must match the order of get_refscan_needles, since users may use that
// function to map back from the found needles to a store path
refscan_needles: get_refscan_needles(derivation)
.map(|path| nixbase32::encode(path.digest()))
.collect(),
command_args,
outputs: {
// produce output_paths, which is the absolute path of each output (sorted)
let mut output_paths: Vec<PathBuf> = derivation
.outputs
.values()
.map(|e| PathBuf::from(e.path_str()[1..].to_owned()))
.collect();
// Sort the outputs. We can use sort_unstable, as these are unique strings.
output_paths.sort_unstable();
output_paths
},
// Turn this into a sorted-by-key Vec<EnvVar>.
environment_vars: environment_vars
.into_iter()
.map(|(key, value)| EnvVar { key, value })
.collect(),
inputs: inputs
.into_iter()
.map(|(path, node)| {
(
path.to_string()
.as_str()
.try_into()
.expect("Tvix bug: unable to convert store path basename to PathComponent"),
node,
)
})
.collect(),
inputs_dir: nix_compat::store_path::STORE_DIR[1..].into(),
constraints,
working_dir: "build".into(),
scratch_paths: vec!["build".into(), "nix/store".into()],
additional_files: additional_files
.into_iter()
.map(|(path, contents)| AdditionalFile {
path: PathBuf::from(path),
contents,
})
.collect(),
})
}
/// handle passAsFile, if set.
/// For each env $x in that list, the original env is removed, and a $xPath
/// environment var added instead, referring to a path inside the build with
/// the contents from the original env var.
fn handle_pass_as_file(
environment_vars: &mut BTreeMap<String, Bytes>,
additional_files: &mut BTreeMap<String, Bytes>,
) -> std::io::Result<()> {
let pass_as_file = environment_vars.get("passAsFile").map(|v| {
// Convert pass_as_file to string.
// When it gets here, it contains a space-separated list of env var
// keys, which must be strings.
String::from_utf8(v.to_vec())
});
if let Some(pass_as_file) = pass_as_file {
let pass_as_file = pass_as_file.map_err(|_| {
std::io::Error::new(
std::io::ErrorKind::InvalidInput,
"passAsFile elements are no valid utf8 strings",
)
})?;
for x in pass_as_file.split(' ') {
match environment_vars.remove_entry(x) {
Some((k, contents)) => {
let (new_k, path) = calculate_pass_as_file_env(&k);
additional_files.insert(path[1..].to_string(), contents);
environment_vars.insert(new_k, Bytes::from(path));
}
None => {
return Err(std::io::Error::new(
std::io::ErrorKind::InvalidData,
"passAsFile refers to non-existent env key",
));
}
}
}
}
Ok(())
}
/// For a given key k in a derivation environment that's supposed to be passed as file,
/// calculate the ${k}Path key and filepath value that it's being replaced with
/// while preparing the build.
/// The filepath is `/build/.attrs-${nixbase32(sha256(key))`.
fn calculate_pass_as_file_env(k: &str) -> (String, String) {
(
format!("{}Path", k),
format!(
"/build/.attr-{}",
nixbase32::encode(&Sha256::new_with_prefix(k).finalize())
),
)
}
#[cfg(test)]
mod test {
use bytes::Bytes;
use nix_compat::{derivation::Derivation, store_path::StorePath};
use std::collections::{BTreeMap, HashSet};
use std::sync::LazyLock;
use tvix_castore::fixtures::DUMMY_DIGEST;
use tvix_castore::{Node, PathComponent};
use tvix_build::buildservice::{AdditionalFile, BuildConstraints, BuildRequest, EnvVar};
use crate::tvix_build::NIX_ENVIRONMENT_VARS;
use super::derivation_to_build_request;
static INPUT_NODE_FOO_NAME: LazyLock<Bytes> =
LazyLock::new(|| "mp57d33657rf34lzvlbpfa1gjfv5gmpg-bar".into());
static INPUT_NODE_FOO: LazyLock<Node> = LazyLock::new(|| Node::Directory {
digest: DUMMY_DIGEST.clone(),
size: 42,
});
#[test]
fn test_derivation_to_build_request() {
let aterm_bytes = include_bytes!("tests/ch49594n9avinrf8ip0aslidkc4lxkqv-foo.drv");
let derivation = Derivation::from_aterm_bytes(aterm_bytes).expect("must parse");
let build_request = derivation_to_build_request(
&derivation,
BTreeMap::from([(
StorePath::<String>::from_bytes(&INPUT_NODE_FOO_NAME.clone()).unwrap(),
INPUT_NODE_FOO.clone(),
)]),
)
.expect("must succeed");
let mut expected_environment_vars = vec![
EnvVar {
key: "bar".into(),
value: "/nix/store/mp57d33657rf34lzvlbpfa1gjfv5gmpg-bar".into(),
},
EnvVar {
key: "builder".into(),
value: ":".into(),
},
EnvVar {
key: "name".into(),
value: "foo".into(),
},
EnvVar {
key: "out".into(),
value: "/nix/store/fhaj6gmwns62s6ypkcldbaj2ybvkhx3p-foo".into(),
},
EnvVar {
key: "system".into(),
value: ":".into(),
},
];
expected_environment_vars.extend(NIX_ENVIRONMENT_VARS.iter().map(|(k, v)| EnvVar {
key: k.to_string(),
value: Bytes::from_static(v.as_bytes()),
}));
expected_environment_vars.sort_unstable_by_key(|e| e.key.to_owned());
assert_eq!(
BuildRequest {
command_args: vec![":".into()],
outputs: vec!["nix/store/fhaj6gmwns62s6ypkcldbaj2ybvkhx3p-foo".into()],
environment_vars: expected_environment_vars,
inputs: BTreeMap::from([(
PathComponent::try_from(INPUT_NODE_FOO_NAME.clone()).unwrap(),
INPUT_NODE_FOO.clone()
)]),
inputs_dir: "nix/store".into(),
constraints: HashSet::from([
BuildConstraints::System(derivation.system.clone()),
BuildConstraints::ProvideBinSh
]),
additional_files: vec![],
working_dir: "build".into(),
scratch_paths: vec!["build".into(), "nix/store".into()],
refscan_needles: vec![
"fhaj6gmwns62s6ypkcldbaj2ybvkhx3p".into(),
"ss2p4wmxijn652haqyd7dckxwl4c7hxx".into()
],
},
build_request
);
}
#[test]
fn test_fod_to_build_request() {
let aterm_bytes = include_bytes!("tests/0hm2f1psjpcwg8fijsmr4wwxrx59s092-bar.drv");
let derivation = Derivation::from_aterm_bytes(aterm_bytes).expect("must parse");
let build_request =
derivation_to_build_request(&derivation, BTreeMap::from([])).expect("must succeed");
let mut expected_environment_vars = vec![
EnvVar {
key: "builder".into(),
value: ":".into(),
},
EnvVar {
key: "name".into(),
value: "bar".into(),
},
EnvVar {
key: "out".into(),
value: "/nix/store/4q0pg5zpfmznxscq3avycvf9xdvx50n3-bar".into(),
},
EnvVar {
key: "outputHash".into(),
value: "08813cbee9903c62be4c5027726a418a300da4500b2d369d3af9286f4815ceba".into(),
},
EnvVar {
key: "outputHashAlgo".into(),
value: "sha256".into(),
},
EnvVar {
key: "outputHashMode".into(),
value: "recursive".into(),
},
EnvVar {
key: "system".into(),
value: ":".into(),
},
];
expected_environment_vars.extend(NIX_ENVIRONMENT_VARS.iter().map(|(k, v)| EnvVar {
key: k.to_string(),
value: Bytes::from_static(v.as_bytes()),
}));
expected_environment_vars.sort_unstable_by_key(|e| e.key.to_owned());
assert_eq!(
BuildRequest {
command_args: vec![":".to_string()],
outputs: vec!["nix/store/4q0pg5zpfmznxscq3avycvf9xdvx50n3-bar".into()],
environment_vars: expected_environment_vars,
inputs: BTreeMap::new(),
inputs_dir: "nix/store".into(),
constraints: HashSet::from([
BuildConstraints::System(derivation.system.clone()),
BuildConstraints::NetworkAccess,
BuildConstraints::ProvideBinSh
]),
additional_files: vec![],
working_dir: "build".into(),
scratch_paths: vec!["build".into(), "nix/store".into()],
refscan_needles: vec!["4q0pg5zpfmznxscq3avycvf9xdvx50n3".into()],
},
build_request
);
}
#[test]
fn test_pass_as_file() {
// (builtins.derivation { "name" = "foo"; passAsFile = ["bar" "baz"]; bar = "baz"; baz = "bar"; system = ":"; builder = ":";}).drvPath
let aterm_bytes = r#"Derive([("out","/nix/store/pp17lwra2jkx8rha15qabg2q3wij72lj-foo","","")],[],[],":",":",[],[("bar","baz"),("baz","bar"),("builder",":"),("name","foo"),("out","/nix/store/pp17lwra2jkx8rha15qabg2q3wij72lj-foo"),("passAsFile","bar baz"),("system",":")])"#.as_bytes();
let derivation = Derivation::from_aterm_bytes(aterm_bytes).expect("must parse");
let build_request =
derivation_to_build_request(&derivation, BTreeMap::from([])).expect("must succeed");
let mut expected_environment_vars = vec![
// Note how bar and baz are not present in the env anymore,
// but replaced with barPath, bazPath respectively.
EnvVar {
key: "barPath".into(),
value: "/build/.attr-1fcgpy7vc4ammr7s17j2xq88scswkgz23dqzc04g8sx5vcp2pppw".into(),
},
EnvVar {
key: "bazPath".into(),
value: "/build/.attr-15l04iksj1280dvhbzdq9ai3wlf8ac2188m9qv0gn81k9nba19ds".into(),
},
EnvVar {
key: "builder".into(),
value: ":".into(),
},
EnvVar {
key: "name".into(),
value: "foo".into(),
},
EnvVar {
key: "out".into(),
value: "/nix/store/pp17lwra2jkx8rha15qabg2q3wij72lj-foo".into(),
},
// passAsFile stays around
EnvVar {
key: "passAsFile".into(),
value: "bar baz".into(),
},
EnvVar {
key: "system".into(),
value: ":".into(),
},
];
expected_environment_vars.extend(NIX_ENVIRONMENT_VARS.iter().map(|(k, v)| EnvVar {
key: k.to_string(),
value: Bytes::from_static(v.as_bytes()),
}));
expected_environment_vars.sort_unstable_by_key(|e| e.key.to_owned());
assert_eq!(
BuildRequest {
command_args: vec![":".to_string()],
outputs: vec!["nix/store/pp17lwra2jkx8rha15qabg2q3wij72lj-foo".into()],
environment_vars: expected_environment_vars,
inputs: BTreeMap::new(),
inputs_dir: "nix/store".into(),
constraints: HashSet::from([
BuildConstraints::System(derivation.system.clone()),
BuildConstraints::ProvideBinSh,
]),
additional_files: vec![
// baz env
AdditionalFile {
path: "build/.attr-15l04iksj1280dvhbzdq9ai3wlf8ac2188m9qv0gn81k9nba19ds"
.into(),
contents: "bar".into()
},
// bar env
AdditionalFile {
path: "build/.attr-1fcgpy7vc4ammr7s17j2xq88scswkgz23dqzc04g8sx5vcp2pppw"
.into(),
contents: "baz".into(),
},
],
working_dir: "build".into(),
scratch_paths: vec!["build".into(), "nix/store".into()],
refscan_needles: vec!["pp17lwra2jkx8rha15qabg2q3wij72lj".into()],
},
build_request
);
}
}
