Unlucky Launcher v0.2.0

首个 iced + Material 3 Expressive 版本的源码快照。
完整历史与日常提交在 dev 分支；main 只放阶段性快照。

crates/core/tests/setting/atomic_write.rs

@@ -0,0 +1,49 @@
+//! 原子写：覆盖语义、父目录创建、不留临时文件、可选读。
+
+use unlucky_core::platform::atomic::{read_optional, tmp_path, write_atomic};
+
+use crate::common::{dir_entries, TempDir};
+
+#[test]
+fn writes_and_replaces_in_place() {
+    let temp = TempDir::new("atomic");
+    let path = temp.child("config/launcher.json");
+
+    write_atomic(&path, b"{\"a\":1}").expect("首次写");
+    assert_eq!(temp.read("config/launcher.json"), "{\"a\":1}");
+
+    write_atomic(&path, b"{\"a\":2}").expect("覆盖写");
+    assert_eq!(temp.read("config/launcher.json"), "{\"a\":2}");
+
+    // 目录里只该有目标文件，临时文件必须被改名掉。
+    assert_eq!(dir_entries(&temp.child("config")), vec!["launcher.json"]);
+}
+
+#[test]
+fn read_optional_distinguishes_missing_from_failure() {
+    let temp = TempDir::new("atomic-read");
+    let path = temp.child("nope.json");
+    assert!(read_optional(&path).expect("读缺失文件").is_none());
+
+    temp.write("here.json", "内容");
+    let bytes = read_optional(&temp.child("here.json"))
+        .expect("读文件")
+        .expect("有内容");
+    assert_eq!(bytes, "内容".as_bytes());
+}
+
+#[test]
+fn tmp_name_stays_in_same_directory() {
+    let temp = TempDir::new("atomic-tmp");
+    let path = temp.child("config/profiles.json");
+    let tmp = tmp_path(&path);
+    assert_eq!(
+        tmp.parent(),
+        path.parent(),
+        "临时文件必须同目录（rename 才原子）"
+    );
+    assert_ne!(tmp, path);
+    let first = tmp_path(&path);
+    let second = tmp_path(&path);
+    assert_ne!(first, second, "并发写要能拿到不同的临时名");
+}