refactor(tvix/nix-compat): move nar writer to tokio r/7898

There's little reason to keep the nar writer using Async{Read,Write}
traits from futures, while everything else async in tvix (and
nix-compat) uses tokio.

Change-Id: I8cd1efcd0dd5bb76471de997603c7b701a5095de
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11391
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Reviewed-by: Brian Olsen <me@griff.name>

6 files changed, 57 insertions, 73 deletions

diff --git a/tvix/Cargo.lock b/tvix/Cargo.lock
index 80b70579b48a..1fff246e86c5 100644
--- a/tvix/Cargo.lock
+++ b/tvix/Cargo.lock
@@ -2187,7 +2187,6 @@ dependencies = [
  "ed25519-dalek",
  "enum-primitive-derive",
  "futures",
- "futures-util",
  "glob",
  "hex-literal",
  "lazy_static",
diff --git a/tvix/Cargo.nix b/tvix/Cargo.nix
index 216dd2c6e1fc..f4bc00bb3c43 100644
--- a/tvix/Cargo.nix
+++ b/tvix/Cargo.nix
@@ -6718,12 +6718,6 @@ rec {
             packageId = "enum-primitive-derive";
           }
           {
-            name = "futures-util";
-            packageId = "futures-util";
-            optional = true;
-            features = [ "io" ];
-          }
-          {
             name = "glob";
             packageId = "glob";
           }
@@ -6814,13 +6808,12 @@ rec {
           }
         ];
         features = {
-          "async" = [ "futures-util" ];
-          "futures-util" = [ "dep:futures-util" ];
+          "async" = [ "tokio" ];
           "pin-project-lite" = [ "dep:pin-project-lite" ];
           "tokio" = [ "dep:tokio" ];
           "wire" = [ "tokio" "pin-project-lite" ];
         };
-        resolvedDefaultFeatures = [ "async" "futures-util" "pin-project-lite" "tokio" "wire" ];
+        resolvedDefaultFeatures = [ "async" "pin-project-lite" "tokio" "wire" ];
       };
       "nom" = rec {
         crateName = "nom";
diff --git a/tvix/nix-compat/Cargo.toml b/tvix/nix-compat/Cargo.toml
index 8056409428fb..674734a0e9d6 100644
--- a/tvix/nix-compat/Cargo.toml
+++ b/tvix/nix-compat/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2021"
 
 [features]
 # async NAR writer
-async = ["futures-util"]
+async = ["tokio"]
 # code emitting low-level packets used in the daemon protocol.
 wire = ["tokio", "pin-project-lite"]
 
@@ -16,7 +16,6 @@ data-encoding = "2.3.3"
 ed25519 = "2.2.3"
 ed25519-dalek = "2.1.0"
 enum-primitive-derive = "0.3.0"
-futures-util = { version = "0.3.30", features = ["io"], optional = true }
 glob = "0.3.0"
 nom = "7.1.3"
 num-traits = "0.2.18"
diff --git a/tvix/nix-compat/src/nar/writer/async.rs b/tvix/nix-compat/src/nar/writer/async.rs
index 11aefab9cba7..a2ce68fc3c9e 100644
--- a/tvix/nix-compat/src/nar/writer/async.rs
+++ b/tvix/nix-compat/src/nar/writer/async.rs
@@ -10,7 +10,7 @@
 //!
 //! ```rust
 //! # futures::executor::block_on(async {
-//! # use futures::io::BufReader;
+//! # use tokio::io::BufReader;
 //! # let some_file: Vec<u8> = vec![0, 1, 2, 3, 4];
 //!
 //! // Output location to write the NAR to.
@@ -31,7 +31,6 @@
 //! ```
 
 use crate::nar::wire;
-use futures_util::{AsyncBufRead, AsyncBufReadExt, AsyncWrite, AsyncWriteExt};
 use std::{
     io::{
         self,
@@ -39,6 +38,7 @@ use std::{
     },
     pin::Pin,
 };
+use tokio::io::{AsyncBufRead, AsyncBufReadExt, AsyncWrite, AsyncWriteExt};
 
 /// Convenience type alias for types implementing [`AsyncWrite`].
 pub type Writer<'a> = dyn AsyncWrite + Unpin + Send + 'a;
diff --git a/tvix/nix-compat/src/nar/writer/test.rs b/tvix/nix-compat/src/nar/writer/test.rs
index 7b1dd1a2a96e..d7f18a49af34 100644
--- a/tvix/nix-compat/src/nar/writer/test.rs
+++ b/tvix/nix-compat/src/nar/writer/test.rs
@@ -11,16 +11,14 @@ fn symlink() {
 }
 
 #[cfg(feature = "async")]
-#[test]
-fn symlink_async() {
+#[tokio::test]
+async fn symlink_async() {
     let mut buf = vec![];
 
-    futures::executor::block_on(async {
-        let node = nar::writer::r#async::open(&mut buf).await.unwrap();
-        node.symlink("/nix/store/somewhereelse".as_bytes())
-            .await
-            .unwrap();
-    });
+    let node = nar::writer::r#async::open(&mut buf).await.unwrap();
+    node.symlink("/nix/store/somewhereelse".as_bytes())
+        .await
+        .unwrap();
 
     assert_eq!(include_bytes!("../tests/symlink.nar"), buf.as_slice());
 }
@@ -42,22 +40,22 @@ fn file() {
 }
 
 #[cfg(feature = "async")]
-#[test]
-fn file_async() {
+#[tokio::test]
+async fn file_async() {
+    use std::io::Cursor;
+
     let mut buf = vec![];
 
-    futures::executor::block_on(async {
-        let node = nar::writer::r#async::open(&mut buf).await.unwrap();
+    let node = nar::writer::r#async::open(&mut buf).await.unwrap();
 
-        let file_contents = "Hello World!".to_string();
-        node.file(
-            false,
-            file_contents.len() as u64,
-            &mut futures::io::Cursor::new(file_contents),
-        )
-        .await
-        .unwrap();
-    });
+    let file_contents = "Hello World!".to_string();
+    node.file(
+        false,
+        file_contents.len() as u64,
+        &mut Cursor::new(file_contents),
+    )
+    .await
+    .unwrap();
 
     assert_eq!(include_bytes!("../tests/helloworld.nar"), buf.as_slice());
 }
@@ -93,41 +91,38 @@ fn complicated() {
 }
 
 #[cfg(feature = "async")]
-#[test]
-fn complicated_async() {
+#[tokio::test]
+async fn complicated_async() {
+    use std::io::Cursor;
+
     let mut buf = vec![];
 
-    futures::executor::block_on(async {
-        let node = nar::writer::r#async::open(&mut buf).await.unwrap();
-
-        let mut dir_node = node.directory().await.unwrap();
-
-        let e = dir_node.entry(".keep".as_bytes()).await.unwrap();
-        e.file(false, 0, &mut futures::io::Cursor::new([]))
-            .await
-            .expect("read .keep must succeed");
-
-        let e = dir_node.entry("aa".as_bytes()).await.unwrap();
-        e.symlink("/nix/store/somewhereelse".as_bytes())
-            .await
-            .expect("symlink must succeed");
-
-        let e = dir_node.entry("keep".as_bytes()).await.unwrap();
-        let mut subdir_node = e.directory().await.expect("directory must succeed");
-
-        let e_sub = subdir_node
-            .entry(".keep".as_bytes())
-            .await
-            .expect("subdir entry must succeed");
-        e_sub
-            .file(false, 0, &mut futures::io::Cursor::new([]))
-            .await
-            .unwrap();
-
-        // close the subdir, and then the dir, which is required.
-        subdir_node.close().await.unwrap();
-        dir_node.close().await.unwrap();
-    });
+    let node = nar::writer::r#async::open(&mut buf).await.unwrap();
+
+    let mut dir_node = node.directory().await.unwrap();
+
+    let e = dir_node.entry(".keep".as_bytes()).await.unwrap();
+    e.file(false, 0, &mut Cursor::new([]))
+        .await
+        .expect("read .keep must succeed");
+
+    let e = dir_node.entry("aa".as_bytes()).await.unwrap();
+    e.symlink("/nix/store/somewhereelse".as_bytes())
+        .await
+        .expect("symlink must succeed");
+
+    let e = dir_node.entry("keep".as_bytes()).await.unwrap();
+    let mut subdir_node = e.directory().await.expect("directory must succeed");
+
+    let e_sub = subdir_node
+        .entry(".keep".as_bytes())
+        .await
+        .expect("subdir entry must succeed");
+    e_sub.file(false, 0, &mut Cursor::new([])).await.unwrap();
+
+    // close the subdir, and then the dir, which is required.
+    subdir_node.close().await.unwrap();
+    dir_node.close().await.unwrap();
 
     assert_eq!(include_bytes!("../tests/complicated.nar"), buf.as_slice());
 }
diff --git a/tvix/store/src/nar/renderer.rs b/tvix/store/src/nar/renderer.rs
index 36d184f3b6c5..0816b8e973c7 100644
--- a/tvix/store/src/nar/renderer.rs
+++ b/tvix/store/src/nar/renderer.rs
@@ -6,7 +6,6 @@ use count_write::CountWrite;
 use nix_compat::nar::writer::r#async as nar_writer;
 use sha2::{Digest, Sha256};
 use tokio::io::{self, AsyncWrite, BufReader};
-use tokio_util::compat::{TokioAsyncReadCompatExt, TokioAsyncWriteCompatExt};
 use tvix_castore::{
     blobservice::BlobService,
     directoryservice::DirectoryService,
@@ -45,7 +44,7 @@ where
 /// necessary lookups as it traverses the structure.
 /// The contents in NAR serialization are writen to the passed [AsyncWrite].
 pub async fn write_nar<W, BS, DS>(
-    w: W,
+    mut w: W,
     proto_root_node: &castorepb::node::Node,
     blob_service: BS,
     directory_service: DS,
@@ -56,7 +55,6 @@ where
     DS: DirectoryService + Send,
 {
     // Initialize NAR writer
-    let mut w = w.compat_write();
     let nar_root_node = nar_writer::open(&mut w)
         .await
         .map_err(RenderError::NARWriterError)?;
@@ -101,7 +99,7 @@ where
                 ))
             })?;
 
-            let blob_reader = match blob_service
+            let mut blob_reader = match blob_service
                 .open_read(&digest)
                 .await
                 .map_err(RenderError::StoreError)?
@@ -117,7 +115,7 @@ where
                 .file(
                     proto_file_node.executable,
                     proto_file_node.size,
-                    &mut blob_reader.compat(),
+                    &mut blob_reader,
                 )
                 .await
                 .map_err(RenderError::NARWriterError)?;