Merge pull request #195 from NobodyXu/feature/atomic-install

src/bins.rs

@@ -4,7 +4,7 @@ use cargo_toml::Product;
 use log::debug;
 use serde::Serialize;
 
-use crate::{BinstallError, PkgFmt, PkgMeta, Template};
+use crate::{atomic_install, atomic_symlink_file, BinstallError, PkgFmt, PkgMeta, Template};
 
 pub struct BinFile {
     pub base_name: String,
@@ -80,18 +80,11 @@ impl BinFile {
     pub fn install_bin(&self) -> Result<(), BinstallError> {
         // TODO: check if file already exists
         debug!(
-            "Copy file from '{}' to '{}'",
+            "Atomically install file from '{}' to '{}'",
             self.source.display(),
             self.dest.display()
         );
-        std::fs::copy(&self.source, &self.dest)?;
-
-        #[cfg(target_family = "unix")]
-        {
-            use std::os::unix::fs::PermissionsExt;
-            debug!("Set permissions 755 on '{}'", self.dest.display());
-            std::fs::set_permissions(&self.dest, std::fs::Permissions::from_mode(0o755))?;
-        }
+        atomic_install(&self.source, &self.dest)?;
 
         Ok(())
     }
@@ -110,21 +103,15 @@ impl BinFile {
             self.link.display(),
             dest.display()
         );
-        #[cfg(target_family = "unix")]
-        std::os::unix::fs::symlink(dest, &self.link)?;
-        #[cfg(target_family = "windows")]
-        std::os::windows::fs::symlink_file(dest, &self.link)?;
+        atomic_symlink_file(dest, &self.link)?;
 
         Ok(())
     }
 
     fn link_dest(&self) -> &Path {
-        #[cfg(target_family = "unix")]
-        {
+        if cfg!(target_family = "unix") {
             Path::new(self.dest.file_name().unwrap())
-        }
-        #[cfg(target_family = "windows")]
-        {
+        } else {
             &self.dest
         }
     }

src/helpers.rs

@@ -1,4 +1,6 @@
 use std::fmt::Debug;
+use std::fs;
+use std::io;
 use std::path::{Path, PathBuf};
 
 use bytes::Bytes;
@@ -8,6 +10,7 @@ use log::debug;
 use once_cell::sync::OnceCell;
 use reqwest::{tls, Client, ClientBuilder, Method, Response};
 use serde::Serialize;
+use tempfile::NamedTempFile;
 use tinytemplate::TinyTemplate;
 use tokio::task::block_in_place;
 use url::Url;
@@ -188,6 +191,91 @@ pub fn get_install_path<P: AsRef<Path>>(install_path: Option<P>) -> Option<PathB
     dir
 }
 
+/// Atomically install a file.
+///
+/// This is a blocking function, must be called in `block_in_place` mode.
+pub fn atomic_install(src: &Path, dst: &Path) -> io::Result<()> {
+    debug!(
+        "Attempting to atomically rename from '{}' to '{}'",
+        src.display(),
+        dst.display()
+    );
+
+    if fs::rename(src, dst).is_err() {
+        debug!("Attempting at atomically failed, fallback to creating tempfile.");
+        // src and dst is not on the same filesystem/mountpoint.
+        // Fallback to creating NamedTempFile on the parent dir of
+        // dst.
+
+        let mut src_file = fs::File::open(src)?;
+
+        let parent = dst.parent().unwrap();
+        debug!("Creating named tempfile at '{}'", parent.display());
+        let mut tempfile = NamedTempFile::new_in(parent)?;
+
+        debug!(
+            "Copying from '{}' to '{}'",
+            src.display(),
+            tempfile.path().display()
+        );
+        io::copy(&mut src_file, tempfile.as_file_mut())?;
+
+        debug!("Retrieving permissions of '{}'", src.display());
+        let permissions = src_file.metadata()?.permissions();
+
+        debug!(
+            "Setting permissions of '{}' to '{permissions:#?}'",
+            tempfile.path().display()
+        );
+        tempfile.as_file().set_permissions(permissions)?;
+
+        debug!(
+            "Persisting '{}' to '{}'",
+            tempfile.path().display(),
+            dst.display()
+        );
+        tempfile.persist(dst).map_err(io::Error::from)?;
+    } else {
+        debug!("Attempting at atomically succeeded.");
+    }
+
+    Ok(())
+}
+
+fn symlink_file<P: AsRef<Path>, Q: AsRef<Path>>(original: P, link: Q) -> io::Result<()> {
+    #[cfg(target_family = "unix")]
+    let f = std::os::unix::fs::symlink;
+    #[cfg(target_family = "windows")]
+    let f = std::os::windows::fs::symlink_file;
+
+    f(original, link)
+}
+
+/// Atomically install symlink "link" to a file "dst".
+///
+/// This is a blocking function, must be called in `block_in_place` mode.
+pub fn atomic_symlink_file(dest: &Path, link: &Path) -> io::Result<()> {
+    let parent = link.parent().unwrap();
+
+    debug!("Creating tempPath at '{}'", parent.display());
+    let temp_path = NamedTempFile::new_in(parent)?.into_temp_path();
+    fs::remove_file(&temp_path)?;
+
+    debug!(
+        "Creating symlink '{}' to file '{}'",
+        temp_path.display(),
+        dest.display()
+    );
+    symlink_file(dest, &temp_path)?;
+
+    debug!(
+        "Persisting '{}' to '{}'",
+        temp_path.display(),
+        link.display()
+    );
+    temp_path.persist(link).map_err(io::Error::from)
+}
+
 pub trait Template: Serialize {
     fn render(&self, template: &str) -> Result<String, BinstallError>
     where