Never lose work: atomic saves (temporary file, flush, rename) keeping the replaced version as <file>.bak; autosave of unsaved changes into a recovery folder (every 5 min, preference autosave_minutes, and after commands over 1.5 s; skipped when unchanged; entries locked while their app runs); Recover unsaved design? at launch; doc.recovery_list / doc.recover / doc.recovery_discard; kill-mid-save test

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

apps/solvecraft-cli/src/main.rs

@@ -55,6 +55,8 @@ fn main() -> ExitCode {
         Some("oracle") => oracle::run(&args[1..]),
         Some("step-corpus") => oracle::step_corpus(&args[1..]),
         Some("mcp") => cmd_mcp(&args[1..]),
+        // Hidden, for the kill-mid-save test: save a large design over and over.
+        Some("save-stress") => cmd_save_stress(&args[1..]),
         Some("--version" | "-V") => {
             println!("solvecraft-cli {}", env!("CARGO_PKG_VERSION"));
             Ok(())
@@ -217,3 +219,25 @@ fn cmd_mcp(args: &[String]) -> Result<(), String> {
     let stdout = std::io::stdout();
     solvecraft_mcp::Server::new(backend).serve(stdin.lock(), stdout.lock()).map_err(|e| e.to_string())
 }
+
+/// `save-stress <path> <rounds>`: save a design of a few hundred kilobytes `rounds` times, its
+/// parameter `save_round` set to the round number each time.
+fn cmd_save_stress(args: &[String]) -> Result<(), String> {
+    let (Some(path), Some(rounds)) = (args.first(), args.get(1).and_then(|n| n.parse::<u64>().ok())) else {
+        return Err("usage: solvecraft-cli save-stress <path> <rounds>".into());
+    };
+    let mut s = Session::default();
+    let filler = (0..3000).map(|i| solvecraft_engine::doc::Param {
+        name: format!("p{i}"),
+        expr: format!("{i} mm + 0.5 mm"),
+        unit: "mm".into(),
+        comment: "filler to make the file large".into(),
+        model: false,
+    });
+    s.doc_mut().params.extend(filler);
+    for r in 0..rounds {
+        s.doc_mut().set_param("save_round", &r.to_string(), None, None).map_err(|e| e.to_string())?;
+        s.execute("SaveDocumentCommand", &json!({ "path": path })).map_err(|e| e.to_string())?;
+    }
+    Ok(())
+}

apps/solvecraft-cli/tests/kill_mid_save.rs

@@ -0,0 +1,45 @@
+//! Kill the process while it saves: the design file is always the old version or the new one,
+//! whole, and opens.
+
+use std::process::Command;
+use std::time::Duration;
+
+fn round_of(path: &std::path::Path) -> Option<String> {
+    let bytes = std::fs::read(path).ok()?;
+    let doc = solvecraft_engine::io::read_design(&bytes).ok()?;
+    doc.params.iter().find(|p| p.name == "save_round").map(|p| p.expr.clone())
+}
+
+#[test]
+fn killed_mid_save_the_old_file_survives() {
+    let exe = env!("CARGO_BIN_EXE_solvecraft-cli");
+    let dir = std::env::temp_dir().join(format!("solvecraft-kill-mid-save-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    let path = dir.join("design.solvecraft");
+    let ok = Command::new(exe).args(["save-stress", &path.to_string_lossy(), "1"]).status().unwrap();
+    assert!(ok.success());
+    assert_eq!(round_of(&path).as_deref(), Some("0"));
+    let mut kills = 0;
+    let mut seen = std::collections::BTreeSet::new();
+    for i in 0..25u64 {
+        let mut child = Command::new(exe).args(["save-stress", &path.to_string_lossy(), "100000"]).spawn().unwrap();
+        // Let it get into its save loop (building the design takes a moment), then kill it.
+        std::thread::sleep(Duration::from_millis(150 + (i * 37) % 200));
+        if child.try_wait().unwrap().is_none() {
+            child.kill().unwrap();
+            kills += 1;
+        }
+        let _ = child.wait();
+        let round = round_of(&path);
+        assert!(round.is_some(), "after kill {i} the design file is torn or missing");
+        seen.insert(round);
+        let bak = solvecraft_engine::io::backup_path(&path);
+        if bak.exists() {
+            assert!(round_of(&bak).is_some(), "after kill {i} the backup is torn");
+        }
+    }
+    assert!(kills > 20, "the saver was killed while running ({kills})");
+    assert!(seen.len() > 5, "the saver got to saving before it was killed ({seen:?})");
+    let _ = std::fs::remove_dir_all(&dir);
+}