Merge slideshow-composer (with main) into slideshow-overlays

crates/engine/src/config.rs

@@ -6,21 +6,42 @@
 //! face- or denoise-models folder until a host asks for one ([`Session::with_default_face_models`],
 //! [`Session::with_default_denoise_models`]), so tests stay hermetic.
 
+use std::ffi::OsString;
 use std::path::PathBuf;
 
 use crate::Session;
 
-/// LightCraft's per-user config folder (`…/LightCraft`), if the platform tells us where.
+#[derive(Clone, Copy)]
+enum Platform {
+    Mac,
+    Windows,
+    Other,
+}
+
+/// LightCraft's settings folder. A nonempty `$LIGHTCRAFT_CONFIG_DIR` overrides the platform default.
+/// The override is the complete directory; no application-name suffix is appended. An explicitly
+/// empty value disables the settings directory instead of falling back to a personal profile.
 pub fn config_dir() -> Option<PathBuf> {
-    if cfg!(target_os = "macos") {
-        std::env::var_os("HOME").map(|h| PathBuf::from(h).join("Library/Application Support/LightCraft"))
+    let platform = if cfg!(target_os = "macos") {
+        Platform::Mac
     } else if cfg!(windows) {
-        std::env::var_os("APPDATA").map(|a| PathBuf::from(a).join("LightCraft"))
+        Platform::Windows
     } else {
-        std::env::var_os("XDG_CONFIG_HOME")
-            .map(PathBuf::from)
-            .or_else(|| std::env::var_os("HOME").map(|h| PathBuf::from(h).join(".config")))
-            .map(|c| c.join("lightcraft"))
+        Platform::Other
+    };
+    config_dir_with(platform, |name| std::env::var_os(name))
+}
+
+fn config_dir_with(platform: Platform, env: impl Fn(&str) -> Option<OsString>) -> Option<PathBuf> {
+    if let Some(dir) = env("LIGHTCRAFT_CONFIG_DIR") {
+        return (!dir.is_empty()).then(|| PathBuf::from(dir));
+    }
+    match platform {
+        Platform::Mac => env("HOME").map(|h| PathBuf::from(h).join("Library/Application Support/LightCraft")),
+        Platform::Windows => env("APPDATA").map(|a| PathBuf::from(a).join("LightCraft")),
+        Platform::Other => {
+            env("XDG_CONFIG_HOME").map(PathBuf::from).or_else(|| env("HOME").map(|h| PathBuf::from(h).join(".config"))).map(|c| c.join("lightcraft"))
+        }
     }
 }
 
@@ -56,3 +77,56 @@ impl Session {
         self.denoise.touch();
     }
 }
+
+#[cfg(test)]
+mod config_tests {
+    use super::*;
+
+    fn resolve(platform: Platform, vars: &[(&str, &str)]) -> Option<PathBuf> {
+        config_dir_with(platform, |name| vars.iter().find_map(|(key, value)| (*key == name).then(|| OsString::from(value))))
+    }
+
+    #[test]
+    fn config_override_wins_without_reading_user_profile() {
+        for platform in [Platform::Mac, Platform::Windows, Platform::Other] {
+            let actual = config_dir_with(platform, |name| {
+                assert_eq!(name, "LIGHTCRAFT_CONFIG_DIR");
+                Some(OsString::from("isolated/settings"))
+            });
+            assert_eq!(actual, Some(PathBuf::from("isolated/settings")));
+        }
+    }
+
+    #[test]
+    fn config_empty_override_disables_profile_without_reading_defaults() {
+        for platform in [Platform::Mac, Platform::Windows, Platform::Other] {
+            assert_eq!(
+                config_dir_with(platform, |name| {
+                    assert_eq!(name, "LIGHTCRAFT_CONFIG_DIR");
+                    Some(OsString::new())
+                }),
+                None
+            );
+        }
+    }
+
+    #[test]
+    fn config_unset_override_keeps_platform_defaults() {
+        let vars = [("HOME", "/user"), ("APPDATA", "/roaming"), ("XDG_CONFIG_HOME", "/xdg")];
+        assert_eq!(resolve(Platform::Mac, &vars), Some(PathBuf::from("/user/Library/Application Support/LightCraft")));
+        assert_eq!(resolve(Platform::Windows, &vars), Some(PathBuf::from("/roaming/LightCraft")));
+        assert_eq!(resolve(Platform::Other, &vars), Some(PathBuf::from("/xdg/lightcraft")));
+        assert_eq!(resolve(Platform::Other, &[("HOME", "/user")]), Some(PathBuf::from("/user/.config/lightcraft")));
+        for platform in [Platform::Mac, Platform::Windows, Platform::Other] {
+            assert_eq!(resolve(platform, &[]), None);
+        }
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn config_override_preserves_non_unicode_paths() {
+        use std::os::unix::ffi::OsStringExt as _;
+        let value = OsString::from_vec(b"isolated/\xff".to_vec());
+        assert_eq!(config_dir_with(Platform::Mac, |_| Some(value.clone())), Some(PathBuf::from(value)));
+    }
+}