refactor(tvix/store): generalize `PathInfo` constructors r/7839

Instead of enforcing NAR SHA256 all the time, we generalize the
`PathInfo` constructor to take a `CAHash` argument which can drive
whether we are having a flat, NAR or text scheme.

With this, it is now possible to implement flat schemes in our
evaluation builtins, e.g. `builtins.path`.

Change-Id: I15bfee0ef4f0f428bfbd2f30c57c012cdcf6a976
Signed-off-by: Ryan Lahfa <tvl@lahfa.xyz>
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11286
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

3 files changed, 63 insertions, 20 deletions

diff --git a/tvix/glue/src/builtins/import.rs b/tvix/glue/src/builtins/import.rs
index 88e483031f46..8c9efc679171 100644
--- a/tvix/glue/src/builtins/import.rs
+++ b/tvix/glue/src/builtins/import.rs
@@ -119,6 +119,7 @@ mod import_builtins {
 
     use super::*;
 
+    use nix_compat::nixhash::{CAHash, NixHash};
     use tvix_eval::generators::Gen;
     use tvix_eval::{generators::GenCo, ErrorKind, Value};
 
@@ -138,8 +139,19 @@ mod import_builtins {
         Ok(state
             .tokio_handle
             .block_on(async {
+                let (_, nar_sha256) = state
+                    .path_info_service
+                    .as_ref()
+                    .calculate_nar(&root_node)
+                    .await?;
+
                 state
-                    .register_node_in_path_info_service(name, &p, root_node)
+                    .register_node_in_path_info_service(
+                        name,
+                        &p,
+                        CAHash::Nar(NixHash::Sha256(nar_sha256)),
+                        root_node,
+                    )
                     .await
             })
             .map_err(|err| ErrorKind::IO {
diff --git a/tvix/glue/src/tvix_store_io.rs b/tvix/glue/src/tvix_store_io.rs
index cbda365c20da..bfdab0846165 100644
--- a/tvix/glue/src/tvix_store_io.rs
+++ b/tvix/glue/src/tvix_store_io.rs
@@ -53,7 +53,8 @@ use crate::tvix_build::derivation_to_build_request;
 pub struct TvixStoreIO {
     blob_service: Arc<dyn BlobService>,
     directory_service: Arc<dyn DirectoryService>,
-    path_info_service: Arc<dyn PathInfoService>,
+    // This is public so builtins can put PathInfos directly.
+    pub(crate) path_info_service: Arc<dyn PathInfoService>,
     std_io: StdIO,
     #[allow(dead_code)]
     build_service: Arc<dyn BuildService>,
@@ -293,9 +294,13 @@ impl TvixStoreIO {
         &self,
         name: &str,
         path: &Path,
+        ca: CAHash,
         root_node: Node,
     ) -> io::Result<(PathInfo, StorePath)> {
         // Ask the PathInfoService for the NAR size and sha256
+        // We always need it no matter what is the actual hash mode
+        // because the path info construct a narinfo which *always*
+        // require a SHA256 of the NAR representation and the NAR size.
         let (nar_size, nar_sha256) = self
             .path_info_service
             .as_ref()
@@ -303,20 +308,22 @@ impl TvixStoreIO {
             .await?;
 
         // Calculate the output path. This might still fail, as some names are illegal.
-        let output_path = nix_compat::store_path::build_nar_based_store_path(&nar_sha256, name)
-            .map_err(|_| {
-                std::io::Error::new(
-                    std::io::ErrorKind::InvalidData,
-                    format!("invalid name: {}", name),
-                )
-            })?;
+        let output_path =
+            nix_compat::store_path::build_ca_path(name, &ca, Vec::<String>::new(), false).map_err(
+                |_| {
+                    std::io::Error::new(
+                        std::io::ErrorKind::InvalidData,
+                        format!("invalid name: {}", 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());
         tvix_store::import::log_node(&root_node, path);
 
         let path_info =
-            tvix_store::import::derive_nar_ca_path_info(nar_size, nar_sha256, root_node);
+            tvix_store::import::derive_nar_ca_path_info(nar_size, nar_sha256, Some(ca), root_node);
 
         Ok((path_info, output_path.to_owned()))
     }
@@ -325,9 +332,10 @@ impl TvixStoreIO {
         &self,
         name: &str,
         path: &Path,
+        ca: CAHash,
         root_node: Node,
     ) -> io::Result<StorePath> {
-        let (path_info, output_path) = self.node_to_path_info(name, path, root_node).await?;
+        let (path_info, output_path) = self.node_to_path_info(name, path, ca, root_node).await?;
         let _path_info = self.path_info_service.as_ref().put(path_info).await?;
 
         Ok(output_path)
diff --git a/tvix/store/src/import.rs b/tvix/store/src/import.rs
index f2e7bdfe5da3..69f68d46a2fa 100644
--- a/tvix/store/src/import.rs
+++ b/tvix/store/src/import.rs
@@ -4,13 +4,27 @@ use tvix_castore::{
     blobservice::BlobService, directoryservice::DirectoryService, proto::node::Node, B3Digest,
 };
 
-use nix_compat::store_path::{self, StorePath};
+use nix_compat::{
+    nixhash::{CAHash, NixHash},
+    store_path::{self, StorePath},
+};
 
 use crate::{
     pathinfoservice::PathInfoService,
     proto::{nar_info, NarInfo, PathInfo},
 };
 
+impl From<CAHash> for nar_info::Ca {
+    fn from(value: CAHash) -> Self {
+        let hash_type: nar_info::ca::Hash = (&value).into();
+        let digest: bytes::Bytes = value.hash().to_string().into();
+        nar_info::Ca {
+            r#type: hash_type.into(),
+            digest,
+        }
+    }
+}
+
 pub fn log_node(node: &Node, path: &Path) {
     match node {
         Node::Directory(directory_node) => {
@@ -54,13 +68,20 @@ pub fn path_to_name(path: &Path) -> std::io::Result<&str> {
         })
 }
 
-/// Takes the NAR size, SHA-256 of the NAR representation and the root node.
-/// Returns the path information object for a content addressed NAR-style (recursive) object.
+/// Takes the NAR size, SHA-256 of the NAR representation, the root node and optionally
+/// a CA hash information.
+///
+/// Returns the path information object for a NAR-style object.
 ///
 /// This [`PathInfo`] can be further filled for signatures, deriver or verified for the expected
 /// hashes.
 #[inline]
-pub fn derive_nar_ca_path_info(nar_size: u64, nar_sha256: [u8; 32], root_node: Node) -> PathInfo {
+pub fn derive_nar_ca_path_info(
+    nar_size: u64,
+    nar_sha256: [u8; 32],
+    ca: Option<CAHash>,
+    root_node: Node,
+) -> PathInfo {
     // assemble the [crate::proto::PathInfo] object.
     PathInfo {
         node: Some(tvix_castore::proto::Node {
@@ -74,10 +95,7 @@ pub fn derive_nar_ca_path_info(nar_size: u64, nar_sha256: [u8; 32], root_node: N
             signatures: vec![],
             reference_names: vec![],
             deriver: None,
-            ca: Some(nar_info::Ca {
-                r#type: nar_info::ca::Hash::NarSha256.into(),
-                digest: nar_sha256.to_vec().into(),
-            }),
+            ca: ca.map(|ca_hash| ca_hash.into()),
         }),
     }
 }
@@ -118,7 +136,12 @@ where
     let root_node = root_node.rename(output_path.to_string().into_bytes().into());
     log_node(&root_node, path.as_ref());
 
-    let path_info = derive_nar_ca_path_info(nar_size, nar_sha256, root_node);
+    let path_info = derive_nar_ca_path_info(
+        nar_size,
+        nar_sha256,
+        Some(CAHash::Nar(NixHash::Sha256(nar_sha256))),
+        root_node,
+    );
 
     // This new [`PathInfo`] that we get back from there might contain additional signatures or
     // information set by the service itself. In this function, we silently swallow it because