feat: add fs-util for reading, writing json files (#9418)

Cargo.lock

@@ -7446,6 +7446,7 @@ dependencies = [
 name = "reth-fs-util"
 version = "1.0.1"
 dependencies = [
+ "serde",
  "serde_json",
  "thiserror",
 ]

crates/fs-util/Cargo.toml

@@ -15,4 +15,5 @@ workspace = true
 
 # misc
 serde_json.workspace = true
+serde.workspace = true
 thiserror.workspace = true

crates/fs-util/src/lib.rs

@@ -6,10 +6,10 @@
     issue_tracker_base_url = "https://github.com/paradigmxyz/reth/issues/"
 )]
 #![cfg_attr(not(test), warn(unused_crate_dependencies))]
-
+use serde::{de::DeserializeOwned, Serialize};
 use std::{
-    fs::{self, ReadDir},
-    io,
+    fs::{self, File, ReadDir},
+    io::{self, BufWriter, Write},
     path::{Path, PathBuf},
 };
 
@@ -223,6 +223,12 @@ pub fn remove_dir_all(path: impl AsRef<Path>) -> Result<()> {
     fs::remove_dir_all(path).map_err(|err| FsPathError::remove_dir(err, path))
 }
 
+/// Wrapper for `File::create`.
+pub fn create_file(path: impl AsRef<Path>) -> Result<fs::File> {
+    let path = path.as_ref();
+    File::create(path).map_err(|err| FsPathError::create_file(err, path))
+}
+
 /// Wrapper for `std::fs::remove_file`
 pub fn remove_file(path: impl AsRef<Path>) -> Result<()> {
     let path = path.as_ref();
@@ -253,3 +259,21 @@ pub fn metadata(path: impl AsRef<Path>) -> Result<fs::Metadata> {
     let path = path.as_ref();
     fs::metadata(path).map_err(|err| FsPathError::metadata(err, path))
 }
+
+/// Reads the JSON file and deserialize it into the provided type.
+pub fn read_json_file<T: DeserializeOwned>(path: &Path) -> Result<T> {
+    // read the file into a byte array first
+    // https://github.com/serde-rs/json/issues/160
+    let bytes = read(path)?;
+    serde_json::from_slice(&bytes)
+        .map_err(|source| FsPathError::ReadJson { source, path: path.into() })
+}
+
+/// Writes the object as a JSON object.
+pub fn write_json_file<T: Serialize>(path: &Path, obj: &T) -> Result<()> {
+    let file = create_file(path)?;
+    let mut writer = BufWriter::new(file);
+    serde_json::to_writer_pretty(&mut writer, obj)
+        .map_err(|source| FsPathError::WriteJson { source, path: path.into() })?;
+    writer.flush().map_err(|e| FsPathError::write(e, path))
+}

crates/net/network/src/manager.rs

@@ -354,11 +354,8 @@ where
     /// `persistent_peers_file`.
     pub fn write_peers_to_file(&self, persistent_peers_file: &Path) -> Result<(), FsPathError> {
         let known_peers = self.all_peers().collect::<Vec<_>>();
-        let known_peers = serde_json::to_string_pretty(&known_peers).map_err(|e| {
-            FsPathError::WriteJson { source: e, path: persistent_peers_file.to_path_buf() }
-        })?;
         persistent_peers_file.parent().map(fs::create_dir_all).transpose()?;
-        fs::write(persistent_peers_file, known_peers)?;
+        reth_fs_util::write_json_file(persistent_peers_file, &known_peers)?;
         Ok(())
     }