//! This module implements a wrapper around tvix-eval's [EvalIO] type,
//! adding functionality which is required by tvix-cli:
//!
//! 1. Marking plain paths known to the reference scanner.
//! 2. Handling the C++ Nix `__corepkgs__`-hack for nixpkgs bootstrapping.
//!
//! All uses of [EvalIO] in tvix-cli must make use of this wrapper,
//! otherwise fundamental features like nixpkgs bootstrapping and hash
//! calculation will not work.
use crate::KnownPaths;
use smol_str::SmolStr;
use std::cell::RefCell;
use std::io;
use std::path::{Path, PathBuf};
use std::rc::Rc;
use tvix_eval::{EvalIO, FileType};
pub(crate) struct TvixIO<T: EvalIO> {
/// Ingested paths must be reported to this known paths tracker
/// for accurate build reference scanning.
known_paths: Rc<RefCell<KnownPaths>>,
// Actual underlying [EvalIO] implementation.
actual: T,
}
impl<T: EvalIO> TvixIO<T> {
pub(crate) fn new(known_paths: Rc<RefCell<KnownPaths>>, actual: T) -> Self {
Self {
known_paths,
actual,
}
}
}
impl<T: EvalIO> EvalIO for TvixIO<T> {
fn store_dir(&self) -> Option<String> {
self.actual.store_dir()
}
fn import_path(&self, path: &Path) -> Result<PathBuf, io::Error> {
let imported_path = self.actual.import_path(path)?;
self.known_paths
.borrow_mut()
.plain(imported_path.to_string_lossy());
Ok(imported_path)
}
fn path_exists(&self, path: &Path) -> Result<bool, io::Error> {
if path.starts_with("/__corepkgs__") {
return Ok(true);
}
self.actual.path_exists(path)
}
fn read_to_string(&self, path: &Path) -> Result<String, io::Error> {
// Bundled version of corepkgs/fetchurl.nix. The counterpart
// of this happens in `main`, where the `nix_path` of the
// evaluation has `nix=/__corepkgs__` added to it.
//
// This workaround is similar to what cppnix does for passing
// the path through.
//
// TODO: this comparison is bad and allocates, we should use
// the sane path library.
if path.starts_with("/__corepkgs__/fetchurl.nix") {
return Ok(include_str!("fetchurl.nix").to_string());
}
self.actual.read_to_string(path)
}
fn read_dir(&self, path: &Path) -> Result<Vec<(SmolStr, FileType)>, io::Error> {
self.actual.read_dir(path)
}
}