feat(tvix/eval): Implement builtins.fetchTarball r/7983

Implement a first pass at the fetchTarball builtin.

This uses much of the same machinery as fetchUrl, but has the extra
complexity that tarballs have to be extracted and imported as store
paths (into the directory- and blob-services) before hashing. That's
reasonably involved due to the structure of those two services.

This is (unfortunately) not easy to test in an automated way, but I've
tested it manually for now and it seems to work:

    tvix-repl> (import ../. {}).third_party.nixpkgs.hello.outPath
    => "/nix/store/dbghhbq1x39yxgkv3vkgfwbxrmw9nfzi-hello-2.12.1" :: string

Co-authored-by: Connor Brewster <cbrewster@hey.com>
Change-Id: I57afc6b91bad617a608a35bb357861e782a864c8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11020
Autosubmit: aspen <root@gws.fyi>
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

4 files changed, 213 insertions, 2 deletions

diff --git a/tvix/castore/Cargo.toml b/tvix/castore/Cargo.toml
index b68922b7ce07..f54bb2ddb5b4 100644
--- a/tvix/castore/Cargo.toml
+++ b/tvix/castore/Cargo.toml
@@ -22,6 +22,7 @@ sled = { version = "0.34.7" }
 thiserror = "1.0.38"
 tokio-stream = { version = "0.1.14", features = ["fs", "net"] }
 tokio-util = { version = "0.7.9", features = ["io", "io-util"] }
+tokio-tar = "0.3.1"
 tokio = { version = "1.32.0", features = ["fs", "macros", "net", "rt", "rt-multi-thread", "signal"] }
 tonic = "0.11.0"
 tower = "0.4.13"
diff --git a/tvix/castore/src/import/archive.rs b/tvix/castore/src/import/archive.rs
new file mode 100644
index 000000000000..d0ae3c67411c
--- /dev/null
+++ b/tvix/castore/src/import/archive.rs
@@ -0,0 +1,201 @@
+#[cfg(target_family = "unix")]
+use std::os::unix::ffi::OsStrExt;
+use std::{
+    collections::HashMap,
+    path::{Path, PathBuf},
+};
+
+use tokio::io::AsyncRead;
+use tokio_stream::StreamExt;
+use tokio_tar::Archive;
+use tracing::{instrument, Level};
+
+use crate::{
+    blobservice::BlobService,
+    directoryservice::{DirectoryPutter, DirectoryService},
+    import::Error,
+    proto::{node::Node, Directory, DirectoryNode, FileNode, SymlinkNode},
+};
+
+/// Ingests elements from the given tar [`Archive`] into a the passed [`BlobService`] and
+/// [`DirectoryService`].
+#[instrument(skip_all, ret(level = Level::TRACE), err)]
+pub async fn ingest_archive<'a, BS, DS, R>(
+    blob_service: BS,
+    directory_service: DS,
+    mut archive: Archive<R>,
+) -> Result<Node, Error>
+where
+    BS: AsRef<dyn BlobService> + Clone,
+    DS: AsRef<dyn DirectoryService>,
+    R: AsyncRead + Unpin,
+{
+    // Since tarballs can have entries in any arbitrary order, we need to
+    // buffer all of the directory metadata so we can reorder directory
+    // contents and entries to meet the requires of the castore.
+
+    // In the first phase, collect up all the regular files and symlinks.
+    let mut paths = HashMap::new();
+    let mut entries = archive.entries().map_err(Error::Archive)?;
+    while let Some(mut entry) = entries.try_next().await.map_err(Error::Archive)? {
+        let path = entry.path().map_err(Error::Archive)?.into_owned();
+        let name = path
+            .file_name()
+            .ok_or_else(|| {
+                Error::Archive(std::io::Error::new(
+                    std::io::ErrorKind::InvalidInput,
+                    "invalid filename in archive",
+                ))
+            })?
+            .as_bytes()
+            .to_vec()
+            .into();
+
+        let node = match entry.header().entry_type() {
+            tokio_tar::EntryType::Regular
+            | tokio_tar::EntryType::GNUSparse
+            | tokio_tar::EntryType::Continuous => {
+                // TODO: If the same path is overwritten in the tarball, we may leave
+                // an unreferenced blob after uploading.
+                let mut writer = blob_service.as_ref().open_write().await;
+                let size = tokio::io::copy(&mut entry, &mut writer)
+                    .await
+                    .map_err(Error::Archive)?;
+                let digest = writer.close().await.map_err(Error::Archive)?;
+                Node::File(FileNode {
+                    name,
+                    digest: digest.into(),
+                    size,
+                    executable: entry.header().mode().map_err(Error::Archive)? & 64 != 0,
+                })
+            }
+            tokio_tar::EntryType::Symlink => Node::Symlink(SymlinkNode {
+                name,
+                target: entry
+                    .link_name()
+                    .map_err(Error::Archive)?
+                    .expect("symlink missing target")
+                    .as_os_str()
+                    .as_bytes()
+                    .to_vec()
+                    .into(),
+            }),
+            // Push a bogus directory marker so we can make sure this directoy gets
+            // created. We don't know the digest and size until after reading the full
+            // tarball.
+            tokio_tar::EntryType::Directory => Node::Directory(DirectoryNode {
+                name,
+                digest: Default::default(),
+                size: 0,
+            }),
+
+            tokio_tar::EntryType::XGlobalHeader | tokio_tar::EntryType::XHeader => continue,
+
+            entry_type => return Err(Error::UnsupportedTarEntry(path, entry_type)),
+        };
+
+        paths.insert(path, node);
+    }
+
+    // In the second phase, construct all of the directories.
+
+    // Collect into a list and then sort so all entries in the same directory
+    // are next to each other.
+    // We can detect boundaries between each directories to determine
+    // when to construct or push directory entries.
+    let mut ordered_paths = paths.into_iter().collect::<Vec<_>>();
+    ordered_paths.sort_by(|a, b| a.0.cmp(&b.0));
+
+    let mut directory_putter = directory_service.as_ref().put_multiple_start();
+
+    // Start with an initial directory at the root.
+    let mut dir_stack = vec![(PathBuf::from(""), Directory::default())];
+
+    async fn pop_directory(
+        dir_stack: &mut Vec<(PathBuf, Directory)>,
+        directory_putter: &mut Box<dyn DirectoryPutter>,
+    ) -> Result<DirectoryNode, Error> {
+        let (path, directory) = dir_stack.pop().unwrap();
+
+        directory
+            .validate()
+            .map_err(|e| Error::InvalidDirectory(path.to_path_buf(), e))?;
+
+        let dir_node = DirectoryNode {
+            name: path
+                .file_name()
+                .unwrap_or_default()
+                .as_bytes()
+                .to_vec()
+                .into(),
+            digest: directory.digest().into(),
+            size: directory.size(),
+        };
+
+        if let Some((_, parent)) = dir_stack.last_mut() {
+            parent.directories.push(dir_node.clone());
+        }
+
+        directory_putter.put(directory).await?;
+
+        Ok(dir_node)
+    }
+
+    fn push_directories(path: &Path, dir_stack: &mut Vec<(PathBuf, Directory)>) {
+        if path == dir_stack.last().unwrap().0 {
+            return;
+        }
+        if let Some(parent) = path.parent() {
+            push_directories(parent, dir_stack);
+        }
+        dir_stack.push((path.to_path_buf(), Directory::default()));
+    }
+
+    for (path, node) in ordered_paths.into_iter() {
+        // Pop stack until the top dir is an ancestor of this entry.
+        loop {
+            let top = dir_stack.last().unwrap();
+            if path.ancestors().any(|ancestor| ancestor == top.0) {
+                break;
+            }
+
+            pop_directory(&mut dir_stack, &mut directory_putter).await?;
+        }
+
+        // For directories, just ensure the directory node exists.
+        if let Node::Directory(_) = node {
+            push_directories(&path, &mut dir_stack);
+            continue;
+        }
+
+        // Push all ancestor directories onto the stack.
+        push_directories(path.parent().unwrap(), &mut dir_stack);
+
+        let top = dir_stack.last_mut().unwrap();
+        debug_assert_eq!(Some(top.0.as_path()), path.parent());
+
+        match node {
+            Node::File(n) => top.1.files.push(n),
+            Node::Symlink(n) => top.1.symlinks.push(n),
+            // We already handled directories above.
+            Node::Directory(_) => unreachable!(),
+        }
+    }
+
+    let mut root_node = None;
+    while !dir_stack.is_empty() {
+        // If the root directory only has 1 directory entry, we return the child entry
+        // instead... weeeee
+        if dir_stack.len() == 1 && dir_stack.last().unwrap().1.directories.len() == 1 {
+            break;
+        }
+        root_node = Some(pop_directory(&mut dir_stack, &mut directory_putter).await?);
+    }
+    let root_node = root_node.expect("no root node");
+
+    let root_digest = directory_putter.close().await?;
+
+    debug_assert_eq!(root_digest.as_slice(), &root_node.digest);
+
+    Ok(Node::Directory(root_node))
+}
diff --git a/tvix/castore/src/import/error.rs b/tvix/castore/src/import/error.rs
index 15dd0664deaa..18c71aa235b8 100644
--- a/tvix/castore/src/import/error.rs
+++ b/tvix/castore/src/import/error.rs
@@ -1,6 +1,6 @@
 use std::{fs::FileType, path::PathBuf};
 
-use crate::Error as CastoreError;
+use crate::{proto::ValidateDirectoryError, Error as CastoreError};
 
 #[derive(Debug, thiserror::Error)]
 pub enum Error {
@@ -19,8 +19,17 @@ pub enum Error {
     #[error("unable to read {0}: {1}")]
     UnableToRead(PathBuf, std::io::Error),
 
+    #[error("error reading from archive: {0}")]
+    Archive(std::io::Error),
+
     #[error("unsupported file {0} type: {1:?}")]
     UnsupportedFileType(PathBuf, FileType),
+
+    #[error("invalid directory contents {0}: {1}")]
+    InvalidDirectory(PathBuf, ValidateDirectoryError),
+
+    #[error("unsupported tar entry {0} type: {1:?}")]
+    UnsupportedTarEntry(PathBuf, tokio_tar::EntryType),
 }
 
 impl From<CastoreError> for Error {
diff --git a/tvix/castore/src/import/mod.rs b/tvix/castore/src/import/mod.rs
index ff27c0fcfd2b..c5887685bbdb 100644
--- a/tvix/castore/src/import/mod.rs
+++ b/tvix/castore/src/import/mod.rs
@@ -1,4 +1,3 @@
-//! Deals with ingesting contents into castore.
 //! The main library function here is [ingest_entries], receiving a stream of
 //! [IngestionEntry].
 //!
@@ -32,6 +31,7 @@ use tracing::instrument;
 mod error;
 pub use error::Error;
 
+pub mod archive;
 pub mod fs;
 
 /// Ingests [IngestionEntry] from the given stream into a the passed [DirectoryService].