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//! Contains builtins that fetch paths from the Internet, or local filesystem.
use super::utils::select_string;
use crate::{
fetchers::{url_basename, Fetch},
tvix_store_io::TvixStoreIO,
};
use nix_compat::nixhash;
use std::rc::Rc;
use tvix_eval::builtin_macros::builtins;
use tvix_eval::generators::Gen;
use tvix_eval::generators::GenCo;
use tvix_eval::{CatchableErrorKind, ErrorKind, Value};
use url::Url;
// Used as a return type for extract_fetch_args, which is sharing some
// parsing code between the fetchurl and fetchTarball builtins.
struct NixFetchArgs {
url: Url,
name: Option<String>,
sha256: Option<[u8; 32]>,
}
// `fetchurl` and `fetchTarball` accept a single argument, which can either be the URL (as string),
// or an attrset, where `url`, `sha256` and `name` keys are allowed.
async fn extract_fetch_args(
co: &GenCo,
args: Value,
) -> Result<Result<NixFetchArgs, CatchableErrorKind>, ErrorKind> {
if let Ok(url_str) = args.to_str() {
// Get the raw bytes, not the ToString repr.
let url_str =
String::from_utf8(url_str.as_bytes().to_vec()).map_err(|_| ErrorKind::Utf8)?;
// Parse the URL.
let url = Url::parse(&url_str).map_err(|e| ErrorKind::TvixError(Rc::new(e)))?;
return Ok(Ok(NixFetchArgs {
url,
name: None,
sha256: None,
}));
}
let attrs = args.to_attrs().map_err(|_| ErrorKind::TypeError {
expected: "attribute set or contextless string",
actual: args.type_of(),
})?;
let url_str = match select_string(co, &attrs, "url").await? {
Ok(s) => s.ok_or_else(|| ErrorKind::AttributeNotFound { name: "url".into() })?,
Err(cek) => return Ok(Err(cek)),
};
let name = match select_string(co, &attrs, "name").await? {
Ok(s) => s,
Err(cek) => return Ok(Err(cek)),
};
let sha256_str = match select_string(co, &attrs, "sha256").await? {
Ok(s) => s,
Err(cek) => return Ok(Err(cek)),
};
// TODO: disallow other attrset keys, to match Nix' behaviour.
// parse the sha256 string into a digest.
let sha256 = match sha256_str {
Some(sha256_str) => {
let nixhash = nixhash::from_str(&sha256_str, Some("sha256"))
// TODO: DerivationError::InvalidOutputHash should be moved to ErrorKind::InvalidHash and used here instead
.map_err(|e| ErrorKind::TvixError(Rc::new(e)))?;
Some(nixhash.digest_as_bytes().try_into().expect("is sha256"))
}
None => None,
};
// Parse the URL.
let url = Url::parse(&url_str).map_err(|e| ErrorKind::TvixError(Rc::new(e)))?;
Ok(Ok(NixFetchArgs { url, name, sha256 }))
}
#[allow(unused_variables)] // for the `state` arg, for now
#[builtins(state = "Rc<TvixStoreIO>")]
pub(crate) mod fetcher_builtins {
use nix_compat::nixhash::NixHash;
use super::*;
/// Consumes a fetch.
/// If there is enough info to calculate the store path without fetching,
/// queue the fetch to be fetched lazily, and return the store path.
/// If there's not enough info to calculate it, do the fetch now, and then
/// return the store path.
fn fetch_lazy(state: Rc<TvixStoreIO>, name: String, fetch: Fetch) -> Result<Value, ErrorKind> {
match fetch
.store_path(&name)
.map_err(|e| ErrorKind::TvixError(Rc::new(e)))?
{
Some(store_path) => {
// Move the fetch to KnownPaths, so it can be actually fetched later.
let sp = state
.known_paths
.borrow_mut()
.add_fetch(fetch, &name)
.expect("Tvix bug: should only fail if the store path cannot be calculated");
debug_assert_eq!(
sp, store_path,
"calculated store path by KnownPaths should match"
);
// Emit the calculated Store Path.
Ok(Value::Path(Box::new(store_path.to_absolute_path().into())))
}
None => {
// If we don't have enough info, do the fetch now.
let (store_path, _root_node) = state
.tokio_handle
.block_on(async { state.fetcher.ingest_and_persist(&name, fetch).await })
.map_err(|e| ErrorKind::TvixError(Rc::new(e)))?;
Ok(Value::Path(Box::new(store_path.to_absolute_path().into())))
}
}
}
#[builtin("fetchurl")]
async fn builtin_fetchurl(
state: Rc<TvixStoreIO>,
co: GenCo,
args: Value,
) -> Result<Value, ErrorKind> {
let args = match extract_fetch_args(&co, args).await? {
Ok(args) => args,
Err(cek) => return Ok(Value::from(cek)),
};
// Derive the name from the URL basename if not set explicitly.
let name = args
.name
.unwrap_or_else(|| url_basename(&args.url).to_owned());
fetch_lazy(
state,
name,
Fetch::URL {
url: args.url,
exp_hash: args.sha256.map(NixHash::Sha256),
},
)
}
#[builtin("fetchTarball")]
async fn builtin_fetch_tarball(
state: Rc<TvixStoreIO>,
co: GenCo,
args: Value,
) -> Result<Value, ErrorKind> {
let args = match extract_fetch_args(&co, args).await? {
Ok(args) => args,
Err(cek) => return Ok(Value::from(cek)),
};
// Name defaults to "source" if not set explicitly.
const DEFAULT_NAME_FETCH_TARBALL: &str = "source";
let name = args
.name
.unwrap_or_else(|| DEFAULT_NAME_FETCH_TARBALL.to_owned());
fetch_lazy(
state,
name,
Fetch::Tarball {
url: args.url,
exp_nar_sha256: args.sha256,
},
)
}
#[builtin("fetchGit")]
async fn builtin_fetch_git(
state: Rc<TvixStoreIO>,
co: GenCo,
args: Value,
) -> Result<Value, ErrorKind> {
Err(ErrorKind::NotImplemented("fetchGit"))
}
}
|
