Desktop: start.log line before Tauri starts (version, args, working folder, pid), so a logon start that dies early leaves a trace

apps/desktop/src-tauri/src/lib.rs

@@ -198,7 +198,25 @@ fn dev_seed(data_dir: &std::path::Path) {
     }
 }
 
+/// One line before Tauri starts: a start at logon that dies early (before the host log exists) still leaves a trace
+/// with its arguments and working folder (a logon start once left no line at all). Best effort, never fails.
+fn early_trace() {
+    use std::io::Write;
+    let base = std::env::var_os("APPDATA").or_else(|| std::env::var_os("XDG_DATA_HOME")).map(std::path::PathBuf::from)
+        .or_else(|| std::env::var_os("HOME").map(|h| std::path::PathBuf::from(h).join(".local/share")));
+    let Some(base) = base else { return };
+    let dir = base.join("dev.storebound.desktop").join("logs");
+    if std::fs::create_dir_all(&dir).is_err() { return }
+    let args: Vec<String> = std::env::args().skip(1).collect();
+    let cwd = std::env::current_dir().map(|d| d.display().to_string()).unwrap_or_default();
+    let secs = std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH).map(|d| d.as_secs()).unwrap_or(0);
+    if let Ok(mut f) = std::fs::OpenOptions::new().create(true).append(true).open(dir.join("start.log")) {
+        let _ = writeln!(f, "{secs} start {} args={args:?} cwd={cwd} pid={}", env!("CARGO_PKG_VERSION"), std::process::id());
+    }
+}
+
 pub fn run() {
+    early_trace();
     linux_webkit_env();
     let app = tauri::Builder::default()
         // single-instance first: a second start (or a storebound:// link) focuses the running app instead