feat: when writing HTML report pages, write temp file and rename

This avoids creating an empty file if the disk is full.

src/pages.rs

@@ -9,7 +9,6 @@
 
 use std::{
     collections::{HashMap, HashSet},
-    fs::write,
     path::{Path, PathBuf},
     sync::mpsc::RecvTimeoutError,
 };
@@ -33,7 +32,7 @@ use crate::{
     msg::{RunId, RunResult},
     notif::NotificationReceiver,
     run::{Run, RunState, Whence},
-    util::{parse_timestamp, rfc822_timestamp},
+    util::{parse_timestamp, rfc822_timestamp, safely_overwrite},
     worker::Worker,
 };
 
@@ -53,7 +52,7 @@ pub enum PageError {
     Timeformat(#[from] time::error::Format),
 
     #[error("failed to write status page to {0}")]
-    Write(PathBuf, #[source] std::io::Error),
+    Write(PathBuf, #[source] crate::util::UtilError),
 
     #[error("no node alias has been set for builder")]
     NoAlias,
@@ -972,7 +971,8 @@ impl StatusPage {
     }
 
     fn write_file(filename: &Path, text: &str) -> Result<(), PageError> {
-        write(filename, text).map_err(|e| PageError::Write(filename.into(), e))?;
+        safely_overwrite(filename, text.as_bytes())
+            .map_err(|err| PageError::Write(filename.into(), err))?;
         Ok(())
     }
 }

src/util.rs

@@ -1,8 +1,10 @@
 use std::{
+    io::Write,
     path::{Path, PathBuf},
     str::FromStr,
 };
 
+use tempfile::NamedTempFile;
 use time::{
     format_description::{well_known::Rfc2822, FormatItem},
     macros::format_description,
@@ -138,6 +140,20 @@ pub fn read_file_as_objectid(filename: &Path) -> Result<ObjectId, UtilError> {
     ObjectId::from_str(s.trim()).map_err(|err| UtilError::ReadObjectId(filename.into(), err))
 }
 
+pub fn safely_overwrite<P: AsRef<Path>>(filename: P, data: &[u8]) -> Result<(), UtilError> {
+    let filename = filename.as_ref();
+    let dirname = filename
+        .parent()
+        .ok_or(UtilError::NoParent(filename.to_path_buf()))?;
+    let mut tmp = NamedTempFile::new_in(dirname)
+        .map_err(|err| UtilError::CreateTemp(dirname.to_path_buf(), err))?;
+    tmp.write_all(data)
+        .map_err(|err| UtilError::WriteTemp(dirname.to_path_buf(), err))?;
+    tmp.persist(filename)
+        .map_err(|err| UtilError::RenameTemp(filename.to_path_buf(), err))?;
+    Ok(())
+}
+
 #[derive(Debug, thiserror::Error)]
 pub enum UtilError {
     #[error("failed to look up node profile")]
@@ -178,4 +194,16 @@ pub enum UtilError {
 
     #[error("failed to read object id from {0}")]
     ReadObjectId(PathBuf, #[source] radicle::cob::object::ParseObjectId),
+
+    #[error("file name to write to doesn't have a parent directory: {0}")]
+    NoParent(PathBuf),
+
+    #[error("failed to create temporary file in directory {0}")]
+    CreateTemp(PathBuf, #[source] std::io::Error),
+
+    #[error("failed to write to temporary file in {0}")]
+    WriteTemp(PathBuf, #[source] std::io::Error),
+
+    #[error("failed to rename temporary file to {0}")]
+    RenameTemp(PathBuf, #[source] tempfile::PersistError),
 }