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//! This module implements logic required for persisting known paths
//! during an evaluation.
//!
//! Tvix needs to be able to keep track of each Nix store path that it
//! knows about during the scope of a single evaluation and its
//! related builds.
//!
//! This data is required to scan derivation inputs for the build
//! references (the "build closure") that they make use of.
//!
//! Please see //tvix/eval/docs/build-references.md for more
//! information.
use crate::refscan::ReferenceScanner;
use std::{
collections::{hash_map, BTreeSet, HashMap},
ops::Index,
};
#[derive(Debug, PartialEq)]
pub enum PathType {
/// A literal derivation (`.drv`-file), and the *names* of its outputs.
Derivation { output_names: BTreeSet<String> },
/// An output of a derivation, its name, and the path of its derivation.
Output { name: String, derivation: String },
/// A plain store path (e.g. source files copied to the store).
Plain,
}
pub struct KnownPaths {
/// All known paths, and their associated [`PathType`].
paths: HashMap<String, PathType>,
}
impl Index<&str> for KnownPaths {
type Output = PathType;
fn index(&self, index: &str) -> &Self::Output {
&self.paths[index]
}
}
impl KnownPaths {
/// Mark a plain path as known.
pub fn plain<S: ToString>(&mut self, path: S) {
self.paths.insert(path.to_string(), PathType::Plain);
}
/// Mark a derivation as known.
pub fn drv<P: ToString, O: ToString>(&mut self, path: P, outputs: &[O]) {
match self.paths.entry(path.to_string()) {
hash_map::Entry::Occupied(mut entry) => {
for output in outputs {
match entry.get_mut() {
PathType::Derivation {
ref mut output_names,
} => {
output_names.insert(output.to_string());
}
// Branches like this explicitly panic right now to find odd
// situations where something unexpected is done with the
// same path being inserted twice as different types.
_ => panic!(
"bug: {} is already a known path, but not a derivation!",
path.to_string()
),
}
}
}
hash_map::Entry::Vacant(entry) => {
let output_names = outputs.iter().map(|o| o.to_string()).collect();
entry.insert(PathType::Derivation { output_names });
}
}
}
/// Mark a derivation output path as known.
pub fn output<P: ToString, N: ToString, D: ToString>(
&mut self,
output_path: P,
name: N,
drv_path: D,
) {
match self.paths.entry(output_path.to_string()) {
hash_map::Entry::Occupied(entry) => {
/* nothing to do, really! */
debug_assert!(
*entry.get()
== PathType::Output {
name: name.to_string(),
derivation: drv_path.to_string(),
}
);
}
hash_map::Entry::Vacant(entry) => {
entry.insert(PathType::Output {
name: name.to_string(),
derivation: drv_path.to_string(),
});
}
}
}
/// Create a reference scanner from the current set of known paths.
pub fn reference_scanner(&self) -> ReferenceScanner {
let candidates = self.paths.keys().map(Clone::clone).collect();
ReferenceScanner::new(candidates)
}
}
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