refactor(tvix/{cli,store}): move TvixStoreIO to tvix-cli crate r/6550

This trait is eval-specific, there's no point in dealing with these
things in tvix-store.

This implements the EvalIO interface for a Tvix store.
The proper place for this glue code (for now) is tvix-cli, which knows
about both tvix-store and tvix-eval.

There's one annoyance with this move: The `tvix-store import` subcommand
previously also used the TvixStoreIO implementation (because it
conveniently did what we wanted).
Some of this code had to be duplicated, mostly logic to calculate the
NAR-based output path and create the PathInfo object.

Some, but potentially more of this can be extracted into helper
functions in a shared crate, and then be used from both TvixStoreIO in
tvix-cli as well as the tvix-store CLI entrypoint.

Change-Id: Ia7515e83c1b54f95baf810fbd8414c5521382d40
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9212
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: flokli <flokli@flokli.de>

3 files changed, 326 insertions, 1 deletions

diff --git a/tvix/cli/src/main.rs b/tvix/cli/src/main.rs
index 5a7342e76593..1980ac1731e7 100644
--- a/tvix/cli/src/main.rs
+++ b/tvix/cli/src/main.rs
@@ -3,6 +3,7 @@ mod errors;
 mod known_paths;
 mod refscan;
 mod tvix_io;
+mod tvix_store_io;
 
 use std::cell::RefCell;
 use std::rc::Rc;
@@ -17,6 +18,7 @@ use tvix_eval::Value;
 use tvix_store::blobservice::MemoryBlobService;
 use tvix_store::directoryservice::MemoryDirectoryService;
 use tvix_store::pathinfoservice::MemoryPathInfoService;
+use tvix_store_io::TvixStoreIO;
 
 #[derive(Parser)]
 struct Args {
@@ -80,7 +82,7 @@ fn interpret(code: &str, path: Option<PathBuf>, args: &Args, explain: bool) -> b
 
     eval.io_handle = Box::new(tvix_io::TvixIO::new(
         known_paths.clone(),
-        tvix_store::TvixStoreIO::new(blob_service, directory_service, path_info_service),
+        TvixStoreIO::new(blob_service, directory_service, path_info_service),
     ));
 
     // bundle fetchurl.nix (used in nixpkgs) by resolving <nix> to
diff --git a/tvix/cli/src/tvix_io.rs b/tvix/cli/src/tvix_io.rs
index b37dfc6a66a3..74f91138bff8 100644
--- a/tvix/cli/src/tvix_io.rs
+++ b/tvix/cli/src/tvix_io.rs
@@ -15,6 +15,7 @@ use std::path::{Path, PathBuf};
 use std::rc::Rc;
 use tvix_eval::{EvalIO, FileType};
 
+// TODO: Merge this together with TvixStoreIO?
 pub(crate) struct TvixIO<T: EvalIO> {
     /// Ingested paths must be reported to this known paths tracker
     /// for accurate build reference scanning.
diff --git a/tvix/cli/src/tvix_store_io.rs b/tvix/cli/src/tvix_store_io.rs
new file mode 100644
index 000000000000..2c673385342f
--- /dev/null
+++ b/tvix/cli/src/tvix_store_io.rs
@@ -0,0 +1,322 @@
+//! This module provides an implementation of EvalIO talking to tvix-store.
+
+use nix_compat::store_path::{self, StorePath};
+use std::{io, path::Path, path::PathBuf, sync::Arc};
+use tracing::{error, instrument, warn};
+use tvix_eval::{EvalIO, FileType, StdIO};
+
+use tvix_store::{
+    blobservice::BlobService,
+    directoryservice::{self, DirectoryService},
+    import,
+    nar::calculate_size_and_sha256,
+    pathinfoservice::PathInfoService,
+    proto::{node::Node, NamedNode, NarInfo, PathInfo},
+    B3Digest,
+};
+
+/// 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 {
+    blob_service: Arc<dyn BlobService>,
+    directory_service: Arc<dyn DirectoryService>,
+    path_info_service: Arc<dyn PathInfoService>,
+    std_io: StdIO,
+}
+
+impl TvixStoreIO {
+    pub fn new(
+        blob_service: Arc<dyn BlobService>,
+        directory_service: Arc<dyn DirectoryService>,
+        path_info_service: Arc<dyn PathInfoService>,
+    ) -> Self {
+        Self {
+            blob_service,
+            directory_service,
+            path_info_service,
+            std_io: StdIO {},
+        }
+    }
+
+    /// for a given [StorePath] and additional [Path] inside the store path,
+    /// look up the [PathInfo], and if it exists, and then use
+    /// [directoryservice::traverse_to] to return the
+    /// [Node] specified by `sub_path`.
+    #[instrument(skip(self), ret, err)]
+    fn store_path_to_root_node(
+        &self,
+        store_path: &StorePath,
+        sub_path: &Path,
+    ) -> Result<Option<Node>, io::Error> {
+        let path_info = {
+            match self.path_info_service.get(store_path.digest)? {
+                // If there's no PathInfo found, early exit
+                None => return Ok(None),
+                Some(path_info) => path_info,
+            }
+        };
+
+        let root_node = {
+            match path_info.node {
+                None => {
+                    warn!(
+                        "returned PathInfo {:?} node is None, this shouldn't happen.",
+                        &path_info
+                    );
+                    return Ok(None);
+                }
+                Some(root_node) => match root_node.node {
+                    None => {
+                        warn!("node for {:?} is None, this shouldn't happen.", &root_node);
+                        return Ok(None);
+                    }
+                    Some(root_node) => root_node,
+                },
+            }
+        };
+
+        Ok(directoryservice::traverse_to(
+            self.directory_service.clone(),
+            root_node,
+            sub_path,
+        )?)
+    }
+
+    /// Imports a given path on the filesystem into the store, and returns the
+    /// [PathInfo] describing the path, that was sent to
+    /// [PathInfoService].
+    /// While not part of the [EvalIO], it's still useful for clients who
+    /// care about the [PathInfo].
+    #[instrument(skip(self), ret, err)]
+    pub fn import_path_with_pathinfo(&self, path: &std::path::Path) -> Result<PathInfo, io::Error> {
+        // Call [import::ingest_path], which will walk over the given path and return a root_node.
+        let root_node = import::ingest_path(
+            self.blob_service.clone(),
+            self.directory_service.clone(),
+            path,
+        )
+        .expect("error during import_path");
+
+        // Render the NAR
+        let (nar_size, nar_sha256) = calculate_size_and_sha256(
+            &root_node,
+            self.blob_service.clone(),
+            self.directory_service.clone(),
+        )
+        .expect("error during nar calculation"); // TODO: handle error
+
+        // TODO: make a path_to_name helper function?
+        let name = path
+            .file_name()
+            .expect("path must not be ..")
+            .to_str()
+            .expect("path must be valid unicode");
+
+        let output_path = store_path::build_nar_based_store_path(&nar_sha256, name);
+
+        // assemble a new root_node with a name that is derived from the nar hash.
+        let root_node = root_node.rename(output_path.to_string().into_bytes().into());
+
+        // assemble the [PathInfo] object.
+        let path_info = PathInfo {
+            node: Some(tvix_store::proto::Node {
+                node: Some(root_node),
+            }),
+            // There's no reference scanning on path contents ingested like this.
+            references: vec![],
+            narinfo: Some(NarInfo {
+                nar_size,
+                nar_sha256: nar_sha256.to_vec().into(),
+                signatures: vec![],
+                reference_names: vec![],
+                // TODO: narinfo for talosctl.src contains `CA: fixed:r:sha256:1x13j5hy75221bf6kz7cpgld9vgic6bqx07w5xjs4pxnksj6lxb6`
+                // do we need this anywhere?
+            }),
+        };
+
+        // put into [PathInfoService], and return the [PathInfo] that we get
+        // back from there (it might contain additional signatures).
+        let path_info = self.path_info_service.put(path_info)?;
+
+        Ok(path_info)
+    }
+}
+
+impl EvalIO for TvixStoreIO {
+    #[instrument(skip(self), ret, err)]
+    fn path_exists(&self, path: &Path) -> Result<bool, io::Error> {
+        if let Ok((store_path, sub_path)) =
+            StorePath::from_absolute_path_full(&path.to_string_lossy())
+        {
+            if self
+                .store_path_to_root_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) -> Result<String, io::Error> {
+        if let Ok((store_path, sub_path)) =
+            StorePath::from_absolute_path_full(&path.to_string_lossy())
+        {
+            if let Some(node) = self.store_path_to_root_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),
+                                )
+                            })?;
+
+                        let reader = {
+                            let resp = self.blob_service.open_read(&digest)?;
+                            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),
+                                    ))?
+                                }
+                            }
+                        };
+
+                        io::read_to_string(reader)
+                    }
+                    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) -> Result<Vec<(bytes::Bytes, FileType)>, io::Error> {
+        if let Ok((store_path, sub_path)) =
+            StorePath::from_absolute_path_full(&path.to_string_lossy())
+        {
+            if let Some(node) = self.store_path_to_root_node(&store_path, &sub_path)? {
+                match node {
+                    Node::Directory(directory_node) => {
+                        // fetch the Directory itself.
+                        let digest = 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.directory_service.get(&digest)? {
+                            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: &std::path::Path) -> Result<PathBuf, std::io::Error> {
+        let path_info = self.import_path_with_pathinfo(path)?;
+
+        // from the [PathInfo], extract the store path (as string).
+        Ok({
+            let mut path = PathBuf::from(nix_compat::store_path::STORE_DIR_WITH_SLASH);
+
+            let root_node_name = path_info.node.unwrap().node.unwrap().get_name().to_vec();
+
+            // This must be a string, otherwise it would have failed validation.
+            let root_node_name = String::from_utf8(root_node_name).unwrap();
+
+            // append to the PathBuf
+            path.push(root_node_name);
+
+            // and return it
+            path
+        })
+    }
+
+    #[instrument(skip(self), ret)]
+    fn store_dir(&self) -> Option<String> {
+        Some("/nix/store".to_string())
+    }
+}