fix: update status page atomically

Signed-off-by: Lars Wirzenius <liw@liw.fi>

src/status.rs

@@ -33,9 +33,10 @@ impl Default for StatusData {
 
 impl StatusData {
     fn write(&self, filename: &Path) -> Result<(), StatusError> {
+        let tmp = filename.with_extension("update");
         let s = serde_json::to_string_pretty(&self).map_err(StatusError::serialize)?;
-        std::fs::write(filename, s.as_bytes())
-            .map_err(|e| StatusError::status_write(filename, e))?;
+        std::fs::write(&tmp, s.as_bytes()).map_err(|e| StatusError::status_write(filename, e))?;
+        std::fs::rename(&tmp, filename).map_err(|e| StatusError::status_rename(filename, e))?;
         Ok(())
     }
 }
@@ -103,6 +104,9 @@ pub enum StatusError {
 
     #[error("failed to write status to file {0}")]
     StatusWrite(PathBuf, #[source] std::io::Error),
+
+    #[error("failed to rename status to file {0}")]
+    StatusRename(PathBuf, #[source] std::io::Error),
 }
 
 impl StatusError {
@@ -117,4 +121,8 @@ impl StatusError {
     fn status_write(filename: &Path, err: std::io::Error) -> Self {
         Self::StatusWrite(filename.into(), err)
     }
+
+    fn status_rename(filename: &Path, err: std::io::Error) -> Self {
+        Self::StatusRename(filename.into(), err)
+    }
 }