Use XDG_DATA_HOME on *nix if no ~/.pkgx

* Fixes #1103
* Ordering is backwards compatible
* Not allowing relative PKGX_DIR which is more sensible and same as pkgx^1

crates/lib/src/config.rs

@@ -42,18 +42,20 @@ fn get_pantry_dir() -> io::Result<PathBuf> {
 }
 
 fn get_pkgx_dir() -> io::Result<PathBuf> {
-    if let Ok(env_dir) = env::var("PKGX_DIR") {
-        let path = PathBuf::from(env_dir);
-        if !path.is_absolute() {
-            return Ok(env::current_dir()?.join(path));
-        } else {
+    if let Ok(path) = env::var("PKGX_DIR") {
+        let path = PathBuf::from(path);
+        if path.is_absolute() {
             return Ok(path);
         }
     }
-    #[cfg(target_os = "macos")]
-    return Ok(dirs_next::home_dir().unwrap().join(".pkgx"));
-    #[cfg(target_os = "linux")]
-    return Ok(dirs_next::home_dir().unwrap().join(".pkgx"));
-    #[cfg(not(any(target_os = "macos", target_os = "linux")))]
-    panic!("Unsupported platform")
+
+    let default = dirs_next::home_dir().map(|x| x.join(".pkgx"));
+
+    if default.clone().is_some_and(|x| x.exists()) {
+        Ok(default.unwrap())
+    } else if let Ok(xdg) = env::var("XDG_DATA_HOME") {
+        Ok(PathBuf::from(xdg).join("pkgx"))
+    } else {
+        Ok(default.unwrap())
+    }
 }

docs/faq.md

@@ -214,11 +214,20 @@ following [semver] syntax:
 
 ## Where does `pkgx` store files
 
-* pkgs are downloaded to `~/.pkgx` (`$PKGX_DIR` overrides)
-* runtime data like the [pantry] is stored in:
-  * `~/Library/Caches/pkgx` on Mac
-  * `${XDG_CACHE_HOME:-$HOME/.cache}/pkgx` on *nix
-  * `%LOCALAPPDATA%/pkgx` on Windows
+Packages are downloaded to `$PKGX_DIR` if set. If not set:
+
+* macOS
+  * `~/Library/Packages` if the directory exists
+  * `~/.pkgx` otherwise
+* *nix
+  * `~/.pkgx` if the directory exists
+  * `${XDG_DATA_HOME:-$HOME/.local/share}/pkgx` otherwise
+
+Some cache data is stored:
+
+* `~/Library/Caches/pkgx` on Mac
+* `${XDG_CACHE_HOME:-$HOME/.cache}/pkgx` on *nix
+* `%LOCALAPPDATA%/pkgx` on Windows
 
 
 ## What happens if two packages provide the same named program?