Optionally back /tmp and /var/tmp with stable host directories

tests/unit/config.rs

@@ -1066,6 +1066,169 @@ fn build_unsetenv_accumulates() {
     assert_eq!(config.unsetenv, vec!["G", "P", "C"]);
 }
 
+#[test]
+fn persistent_tmp_off_by_default() {
+    let config = build(args_with_command(), None).unwrap();
+    assert!(config.persistent_tmp_key.is_none());
+}
+
+#[test]
+fn persistent_tmp_enabled_via_cli_derives_a_key() {
+    let args = Args {
+        persistent_tmp: true,
+        ..args_with_command()
+    };
+    let config = build(args, None).unwrap();
+    let key = config.persistent_tmp_key.expect("expected derived key");
+    assert_eq!(key.len(), 12);
+    assert!(key.chars().all(|c| c.is_ascii_hexdigit()));
+}
+
+#[test]
+fn persistent_tmp_enabled_via_config() {
+    let file_config = FileConfig {
+        options: Options {
+            persistent_tmp: Some(true),
+            ..Options::default()
+        },
+        ..FileConfig::default()
+    };
+    let config = build(args_with_command(), Some(file_config)).unwrap();
+    assert!(config.persistent_tmp_key.is_some());
+}
+
+#[test]
+fn persistent_key_override_replaces_hash() {
+    let args = Args {
+        persistent_tmp: true,
+        persistent_key: Some("my-label".into()),
+        ..args_with_command()
+    };
+    let config = build(args, None).unwrap();
+    assert_eq!(config.persistent_tmp_key.as_deref(), Some("my-label"));
+}
+
+#[test]
+fn persistent_key_alone_is_ignored_without_persistent_tmp() {
+    let args = Args {
+        persistent_key: Some("my-label".into()),
+        ..args_with_command()
+    };
+    let config = build(args, None).unwrap();
+    assert!(config.persistent_tmp_key.is_none());
+}
+
+#[test]
+fn persistent_tmp_is_noop_in_blacklist_mode() {
+    let derived = build(
+        Args {
+            persistent_tmp: true,
+            blacklist: true,
+            ..args_with_command()
+        },
+        None,
+    )
+    .unwrap();
+    assert!(derived.persistent_tmp_key.is_none());
+
+    let explicit = build(
+        Args {
+            persistent_tmp: true,
+            blacklist: true,
+            persistent_key: Some("explicit".into()),
+            ..args_with_command()
+        },
+        None,
+    )
+    .unwrap();
+    assert!(explicit.persistent_tmp_key.is_none());
+}
+
+#[test]
+fn persistent_tmp_cli_no_overrides_config() {
+    let file_config = FileConfig {
+        options: Options {
+            persistent_tmp: Some(true),
+            ..Options::default()
+        },
+        ..FileConfig::default()
+    };
+    let args = Args {
+        no_persistent_tmp: true,
+        ..args_with_command()
+    };
+    let config = build(args, Some(file_config)).unwrap();
+    assert!(config.persistent_tmp_key.is_none());
+}
+
+#[test]
+fn persistent_tmp_uses_leaf_profile_name() {
+    let file_config = FileConfig {
+        profiles: HashMap::from([
+            (
+                "parent".into(),
+                Options {
+                    ..Options::default()
+                },
+            ),
+            (
+                "leaf".into(),
+                Options {
+                    profile: Some("parent".into()),
+                    persistent_tmp: Some(true),
+                    ..Options::default()
+                },
+            ),
+        ]),
+        ..FileConfig::default()
+    };
+
+    let leaf_args = Args {
+        profile: Some("leaf".into()),
+        ..args_with_command()
+    };
+    let parent_args = Args {
+        profile: Some("leaf".into()),
+        ..args_with_command()
+    };
+    // Same profile selected: same key.
+    let key1 = build(leaf_args, Some(clone_file_config(&file_config)))
+        .unwrap()
+        .persistent_tmp_key
+        .unwrap();
+    let key2 = build(parent_args, Some(clone_file_config(&file_config)))
+        .unwrap()
+        .persistent_tmp_key
+        .unwrap();
+    assert_eq!(key1, key2);
+
+    // Selecting the parent directly (with persistent_tmp injected) should
+    // produce a different key because the leaf profile name differs.
+    let mut file_config2 = clone_file_config(&file_config);
+    file_config2
+        .profiles
+        .get_mut("parent")
+        .unwrap()
+        .persistent_tmp = Some(true);
+    let parent_direct = Args {
+        profile: Some("parent".into()),
+        ..args_with_command()
+    };
+    let key3 = build(parent_direct, Some(file_config2))
+        .unwrap()
+        .persistent_tmp_key
+        .unwrap();
+    assert_ne!(key1, key3);
+}
+
+fn clone_file_config(src: &FileConfig) -> FileConfig {
+    FileConfig {
+        options: src.options.clone(),
+        profiles: src.profiles.clone(),
+        ..FileConfig::default()
+    }
+}
+
 #[test]
 fn build_mask_accumulates() {
     let file_config = FileConfig {