//! This module provides an implementation of EvalIO talking to tvix-store.
use nix_compat::store_path::StorePath;
use std::{
io,
path::{Path, PathBuf},
};
use tokio::io::AsyncReadExt;
use tracing::{error, instrument, warn};
use tvix_eval::{EvalIO, FileType, StdIO};
use tvix_castore::{
blobservice::BlobService,
directoryservice::{self, DirectoryService},
proto::node::Node,
B3Digest,
};
use tvix_store::pathinfoservice::PathInfoService;
/// Implements [EvalIO], asking given [PathInfoService], [DirectoryService]
/// and [BlobService].
///
/// In case the given path does not exist in these stores, we ask StdIO.
/// This is to both cover cases of syntactically valid store paths, that exist
/// on the filesystem (still managed by Nix), as well as being able to read
/// files outside store paths.
pub struct TvixStoreIO<BS, DS, PS> {
blob_service: BS,
directory_service: DS,
path_info_service: PS,
std_io: StdIO,
tokio_handle: tokio::runtime::Handle,
}
impl<BS, DS, PS> TvixStoreIO<BS, DS, PS>
where
DS: AsRef<dyn DirectoryService>,
PS: AsRef<dyn PathInfoService>,
{
pub fn new(
blob_service: BS,
directory_service: DS,
path_info_service: PS,
tokio_handle: tokio::runtime::Handle,
) -> Self {
Self {
blob_service,
directory_service,
path_info_service,
std_io: StdIO {},
tokio_handle,
}
}
/// for a given [StorePath] and additional [Path] inside the store path,
/// look up the [PathInfo], and if it exists, and then use
/// [directoryservice::descend_to] to return the
/// [Node] specified by `sub_path`.
///
/// In case there is no PathInfo yet, this means we need to build it
/// (which currently is stubbed out still).
#[instrument(skip(self), ret, err)]
fn store_path_to_node(
&self,
store_path: &StorePath,
sub_path: &Path,
) -> io::Result<Option<Node>> {
let root_node = match self
.tokio_handle
.block_on(async {
self.path_info_service
.as_ref()
.get(*store_path.digest())
.await
})
.unwrap()
{
// if we have a PathInfo, we know there will be a root_node (due to validation)
Some(path_info) => path_info.node.expect("no node").node.expect("no node"),
// If there's no PathInfo found, we didn't build that path yet.
// and have to trigger the build (and probably insert into the
// PathInfoService (which requires refscan))
// FUTUREWORK: We don't do builds yet, so log a warning and let
// std_io take over.
// In the future, not getting a root node means a failed build!
None => {
warn!("would trigger build, skipping");
return Ok(None);
}
};
// with the root_node and sub_path, descend to the node requested.
Ok(self.tokio_handle.block_on({
async {
directoryservice::descend_to(self.directory_service.as_ref(), root_node, sub_path)
.await
}
})?)
}
}
impl<BS, DS, PS> EvalIO for TvixStoreIO<BS, DS, PS>
where
BS: AsRef<dyn BlobService> + Clone,
DS: AsRef<dyn DirectoryService>,
PS: AsRef<dyn PathInfoService>,
{
#[instrument(skip(self), ret, err)]
fn path_exists(&self, path: &Path) -> io::Result<bool> {
if let Ok((store_path, sub_path)) =
StorePath::from_absolute_path_full(&path.to_string_lossy())
{
if self.store_path_to_node(&store_path, &sub_path)?.is_some() {
Ok(true)
} else {
// As tvix-store doesn't manage /nix/store on the filesystem,
// we still need to also ask self.std_io here.
self.std_io.path_exists(path)
}
} else {
// The store path is no store path, so do regular StdIO.
self.std_io.path_exists(path)
}
}
#[instrument(skip(self), ret, err)]
fn read_to_string(&self, path: &Path) -> io::Result<String> {
if let Ok((store_path, sub_path)) =
StorePath::from_absolute_path_full(&path.to_string_lossy())
{
if let Some(node) = self.store_path_to_node(&store_path, &sub_path)? {
// depending on the node type, treat read_to_string differently
match node {
Node::Directory(_) => {
// This would normally be a io::ErrorKind::IsADirectory (still unstable)
Err(io::Error::new(
io::ErrorKind::Unsupported,
format!("tried to read directory at {:?} to string", path),
))
}
Node::File(file_node) => {
let digest: B3Digest =
file_node.digest.clone().try_into().map_err(|_e| {
error!(
file_node = ?file_node,
"invalid digest"
);
io::Error::new(
io::ErrorKind::InvalidData,
format!("invalid digest length in file node: {:?}", file_node),
)
})?;
self.tokio_handle.block_on(async {
let mut reader = {
let resp = self.blob_service.as_ref().open_read(&digest).await?;
match resp {
Some(blob_reader) => blob_reader,
None => {
error!(
blob.digest = %digest,
"blob not found",
);
Err(io::Error::new(
io::ErrorKind::NotFound,
format!("blob {} not found", &digest),
))?
}
}
};
let mut buf = String::new();
reader.read_to_string(&mut buf).await?;
Ok(buf)
})
}
Node::Symlink(_symlink_node) => Err(io::Error::new(
io::ErrorKind::Unsupported,
"read_to_string for symlinks is unsupported",
))?,
}
} else {
// As tvix-store doesn't manage /nix/store on the filesystem,
// we still need to also ask self.std_io here.
self.std_io.read_to_string(path)
}
} else {
// The store path is no store path, so do regular StdIO.
self.std_io.read_to_string(path)
}
}
#[instrument(skip(self), ret, err)]
fn read_dir(&self, path: &Path) -> io::Result<Vec<(bytes::Bytes, FileType)>> {
if let Ok((store_path, sub_path)) =
StorePath::from_absolute_path_full(&path.to_string_lossy())
{
if let Some(node) = self.store_path_to_node(&store_path, &sub_path)? {
match node {
Node::Directory(directory_node) => {
// fetch the Directory itself.
let digest: B3Digest =
directory_node.digest.clone().try_into().map_err(|_e| {
io::Error::new(
io::ErrorKind::InvalidData,
format!(
"invalid digest length in directory node: {:?}",
directory_node
),
)
})?;
if let Some(directory) = self.tokio_handle.block_on(async {
self.directory_service.as_ref().get(&digest).await
})? {
let mut children: Vec<(bytes::Bytes, FileType)> = Vec::new();
for node in directory.nodes() {
children.push(match node {
Node::Directory(e) => (e.name, FileType::Directory),
Node::File(e) => (e.name, FileType::Regular),
Node::Symlink(e) => (e.name, FileType::Symlink),
})
}
Ok(children)
} else {
// If we didn't get the directory node that's linked, that's a store inconsistency!
error!(
directory.digest = %digest,
path = ?path,
"directory not found",
);
Err(io::Error::new(
io::ErrorKind::NotFound,
format!("directory {digest} does not exist"),
))?
}
}
Node::File(_file_node) => {
// This would normally be a io::ErrorKind::NotADirectory (still unstable)
Err(io::Error::new(
io::ErrorKind::Unsupported,
"tried to readdir path {:?}, which is a file",
))?
}
Node::Symlink(_symlink_node) => Err(io::Error::new(
io::ErrorKind::Unsupported,
"read_dir for symlinks is unsupported",
))?,
}
} else {
self.std_io.read_dir(path)
}
} else {
self.std_io.read_dir(path)
}
}
#[instrument(skip(self), ret, err)]
fn import_path(&self, path: &Path) -> io::Result<PathBuf> {
let output_path = self.tokio_handle.block_on(async {
tvix_store::utils::import_path(
path,
&self.blob_service,
&self.directory_service,
&self.path_info_service,
)
.await
})?;
Ok(output_path.to_absolute_path().into())
}
#[instrument(skip(self), ret)]
fn store_dir(&self) -> Option<String> {
Some("/nix/store".to_string())
}
}
#[cfg(test)]
mod tests {
use std::{cell::RefCell, path::Path, rc::Rc, sync::Arc};
use tempfile::TempDir;
use tvix_castore::{
blobservice::{BlobService, MemoryBlobService},
directoryservice::{DirectoryService, MemoryDirectoryService},
};
use tvix_eval::EvaluationResult;
use tvix_store::pathinfoservice::{MemoryPathInfoService, PathInfoService};
use crate::{builtins::add_derivation_builtins, known_paths::KnownPaths};
use super::TvixStoreIO;
/// evaluates a given nix expression and returns the result.
/// Takes care of setting up the evaluator so it knows about the
// `derivation` builtin.
fn eval(str: &str) -> EvaluationResult {
let mut eval = tvix_eval::Evaluation::new_impure();
let blob_service = Arc::new(MemoryBlobService::default()) as Arc<dyn BlobService>;
let directory_service =
Arc::new(MemoryDirectoryService::default()) as Arc<dyn DirectoryService>;
let path_info_service = Box::new(MemoryPathInfoService::new(
blob_service.clone(),
directory_service.clone(),
)) as Box<dyn PathInfoService>;
let runtime = tokio::runtime::Runtime::new().unwrap();
eval.io_handle = Box::new(TvixStoreIO::new(
blob_service,
directory_service,
path_info_service,
runtime.handle().clone(),
));
let known_paths: Rc<RefCell<KnownPaths>> = Default::default();
add_derivation_builtins(&mut eval, known_paths.clone());
// run the evaluation itself.
eval.evaluate(str, None)
}
/// Helper function that takes a &Path, and invokes a tvix evaluator coercing that path to a string
/// (via "${/this/path}"). The path can be both absolute or not.
/// It returns Option<String>, depending on whether the evaluation succeeded or not.
fn import_path_and_compare<P: AsRef<Path>>(p: P) -> Option<String> {
// Try to import the path using "${/tmp/path/to/test}".
// The format string looks funny, the {} passed to Nix needs to be
// escaped.
let code = format!(r#""${{{}}}""#, p.as_ref().display());
let result = eval(&code);
if !result.errors.is_empty() {
return None;
}
let value = result.value.expect("must be some");
match value {
tvix_eval::Value::String(s) => return Some(s.as_str().to_owned()),
_ => panic!("unexpected value type: {:?}", value),
}
}
/// Import a directory with a zero-sized ".keep" regular file.
/// Ensure it matches the (pre-recorded) store path that Nix would produce.
#[test]
fn import_directory() {
let tmpdir = TempDir::new().unwrap();
// create a directory named "test"
let src_path = tmpdir.path().join("test");
std::fs::create_dir(&src_path).unwrap();
// write a regular file `.keep`.
std::fs::write(src_path.join(".keep"), vec![]).unwrap();
// importing the path with .../test at the end.
assert_eq!(
Some("/nix/store/gq3xcv4xrj4yr64dflyr38acbibv3rm9-test".to_string()),
import_path_and_compare(&src_path)
);
// importing the path with .../test/. at the end.
assert_eq!(
Some("/nix/store/gq3xcv4xrj4yr64dflyr38acbibv3rm9-test".to_string()),
import_path_and_compare(src_path.join("."))
);
}
/// Import a file into the store. Nix uses the "recursive"/NAR-based hashing
/// scheme for these.
#[test]
fn import_file() {
let tmpdir = TempDir::new().unwrap();
// write a regular file `empty`.
std::fs::write(tmpdir.path().join("empty"), vec![]).unwrap();
assert_eq!(
Some("/nix/store/lx5i78a4izwk2qj1nq8rdc07y8zrwy90-empty".to_string()),
import_path_and_compare(tmpdir.path().join("empty"))
);
// write a regular file `hello.txt`.
std::fs::write(tmpdir.path().join("hello.txt"), b"Hello World!").unwrap();
assert_eq!(
Some("/nix/store/925f1jb1ajrypjbyq7rylwryqwizvhp0-hello.txt".to_string()),
import_path_and_compare(tmpdir.path().join("hello.txt"))
);
}
/// Invoke toString on a nonexisting file, and access the .file attribute.
/// This should not cause an error, because it shouldn't trigger an import,
/// and leave the path as-is.
#[test]
fn nonexisting_path_without_import() {
let result = eval("toString ({ line = 42; col = 42; file = /deep/thought; }.file)");
assert!(result.errors.is_empty(), "expect evaluation to succeed");
let value = result.value.expect("must be some");
match value {
tvix_eval::Value::String(s) => {
assert_eq!("/deep/thought", s.as_str());
}
_ => panic!("unexpected value type: {:?}", value),
}
}
}
