[codex] Truncate export files when rewriting

src/export/mod.rs

@@ -1,4 +1,4 @@
-use std::fs::{File, OpenOptions};
+use std::fs::File;
 use std::io::Write;
 
 mod asciidoc;
@@ -156,7 +156,8 @@ impl ExportManager {
 
 /// Write the given content to a file with the specified name
 fn write_to_file(filename: &str, content: &[u8]) -> Result<()> {
-    let mut file = OpenOptions::new().write(true).open(filename)?;
+    let mut file = File::create(filename)
+        .with_context(|| format!("Could not create export file '{filename}'"))?;
     file.write_all(content)
         .with_context(|| format!("Failed to export results to '{filename}'"))
 }

src/export/tests.rs

@@ -1,11 +1,23 @@
-use super::Exporter;
+use super::{write_to_file, Exporter};
 use crate::benchmark::benchmark_result::BenchmarkResult;
 use crate::export::asciidoc::AsciidocExporter;
 use crate::export::orgmode::OrgmodeExporter;
 use crate::util::units::Unit;
 use crate::{export::markdown::MarkdownExporter, options::SortOrder};
 use std::collections::BTreeMap;
 
+#[test]
+fn write_to_file_truncates_existing_content() {
+    let tempdir = tempfile::tempdir().unwrap();
+    let path = tempdir.path().join("results.md");
+    let filename = path.to_str().unwrap();
+
+    write_to_file(filename, b"long benchmark export").unwrap();
+    write_to_file(filename, b"short").unwrap();
+
+    assert_eq!(std::fs::read_to_string(path).unwrap(), "short");
+}
+
 fn get_output<E: Exporter + Default>(
     results: &[BenchmarkResult],
     unit: Option<Unit>,