Use XDG_DATA_HOME on *nix if no ~/.pkgx

Fixes #1103

Author: mxcl

crates/lib/src/config.rs

@@ -1,4 +1,5 @@
 use std::env;
+use std::fs;
 use std::io;
 use std::path::PathBuf;
 
@@ -42,18 +43,28 @@ 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 let Ok(path) = env::var("PKGX_DIR").map(PathBuf::from) {
         if !path.is_absolute() {
-            return Ok(env::current_dir()?.join(path));
+            Ok(env::current_dir()?.join(path))
         } else {
-            return Ok(path);
+            Ok(path)
+        }
+    } else {
+        let home = dirs_next::home_dir();
+        let default = home.clone().map(|x| x.join(".pkgx"));
+
+        #[cfg(target_os = "macos")]
+        if let Some(true) = home.clone().map(|x| x.join("Library/Packages").exists()) {
+            Ok(home.unwrap().join("Library/Packages"))
+        } else {
+            Ok(default.unwrap())
+        }
+
+        #[cfg(not(target_os = "macos"))]
+        if let Some(true) = default.clone().map(|x| x.exists()) {
+            Ok(default.unwrap())
+        } else {
+            Ok(dirs_next::data_local_dir().unwrap().join("pkgx"))
         }
     }
-    #[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")
 }

docs/faq.md

@@ -214,8 +214,17 @@ following [semver] syntax:
 
 ## Where does `pkgx` store files
 
-* pkgs are downloaded to `~/.pkgx` (`$PKGX_DIR` overrides)
-* runtime data like the [pantry] is stored in:
+Packages are downloaded to `$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