Use directories for autoloading (#13382)

fixes https://github.com/nushell/nushell/issues/13378

# Description

This PR tries to improve usage of system APIs to determine the location
of vendored autoload files.

# User-Facing Changes
The paths listed in #13180 and #13217 are changing. This has not been
part of a release yet, so arguably the user facing changes are only to
unreleased features anyway.

# Tests + Formatting
Haven't done, but if someone wants to help me here, I'm open to doing
it. I just don't know how to properly test this.

# After Submitting

Cargo.lock

@@ -3344,6 +3344,8 @@ dependencies = [
  "chrono",
  "chrono-humanize",
  "convert_case",
+ "dirs",
+ "dirs-sys",
  "fancy-regex",
  "indexmap",
  "log",
@@ -3367,6 +3369,7 @@ dependencies = [
  "tempfile",
  "thiserror",
  "typetag",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]

Cargo.toml

@@ -84,6 +84,7 @@ deunicode = "1.6.0"
 dialoguer = { default-features = false, version = "0.11" }
 digest = { default-features = false, version = "0.10" }
 dirs = "5.0"
+dirs-sys = "0.4"
 dtparse = "2.0"
 encoding_rs = "0.8"
 fancy-regex = "0.13"
@@ -178,6 +179,7 @@ v_htmlescape = "0.15.0"
 wax = "0.6"
 which = "6.0.0"
 windows = "0.54"
+windows-sys = "0.48"
 winreg = "0.52"
 
 [dependencies]

crates/nu-cli/tests/completions/mod.rs

@@ -833,7 +833,7 @@ fn variables_completions() {
         "plugin-path".into(),
         "startup-time".into(),
         "temp-path".into(),
-        "vendor-autoload-dir".into(),
+        "vendor-autoload-dirs".into(),
     ];
 
     // Match results

crates/nu-protocol/Cargo.toml

@@ -23,6 +23,7 @@ byte-unit = { version = "5.1", features = [ "serde" ] }
 chrono = { workspace = true, features = [ "serde", "std", "unstable-locales" ], default-features = false }
 chrono-humanize = { workspace = true }
 convert_case = { workspace = true }
+dirs = { workspace = true }
 fancy-regex = { workspace = true }
 indexmap = { workspace = true }
 lru = { workspace = true }
@@ -38,6 +39,10 @@ log = { workspace = true }
 [target.'cfg(unix)'.dependencies]
 nix = { workspace = true, default-features = false, features = ["signal"] }
 
+[target.'cfg(windows)'.dependencies]
+dirs-sys = { workspace = true }
+windows-sys = { workspace = true }
+
 [features]
 plugin = [
   "brotli",

crates/nu-protocol/src/eval_const.rs

@@ -185,24 +185,15 @@ pub(crate) fn create_nu_constant(engine_state: &EngineState, span: Span) -> Valu
         },
     );
 
-    // Create a system level directory for nushell scripts, modules, completions, etc
-    // that can be changed by setting the NU_VENDOR_AUTOLOAD_DIR env var on any platform
-    // before nushell is compiled OR if NU_VENDOR_AUTOLOAD_DIR is not set for non-windows
-    // systems, the PREFIX env var can be set before compile and used as PREFIX/nushell/vendor/autoload
     record.push(
-        "vendor-autoload-dir",
-        // pseudo code
-        // if env var NU_VENDOR_AUTOLOAD_DIR is set, in any platform, use it
-        // if not, if windows, use ALLUSERPROFILE\nushell\vendor\autoload
-        // if not, if non-windows, if env var PREFIX is set, use PREFIX/share/nushell/vendor/autoload
-        // if not, use the default /usr/share/nushell/vendor/autoload
-
-        // check to see if NU_VENDOR_AUTOLOAD_DIR env var is set, if not, use the default
-        if let Some(path) = get_vendor_autoload_dir(engine_state) {
-            Value::string(path.to_string_lossy(), span)
-        } else {
-            Value::error(ShellError::ConfigDirNotFound { span: Some(span) }, span)
-        },
+        "vendor-autoload-dirs",
+        Value::list(
+            get_vendor_autoload_dirs(engine_state)
+                .iter()
+                .map(|path| Value::string(path.to_string_lossy(), span))
+                .collect(),
+            span,
+        ),
     );
 
     record.push("temp-path", {
@@ -259,39 +250,95 @@ pub(crate) fn create_nu_constant(engine_state: &EngineState, span: Span) -> Valu
     Value::record(record, span)
 }
 
-pub fn get_vendor_autoload_dir(engine_state: &EngineState) -> Option<PathBuf> {
-    // pseudo code
-    // if env var NU_VENDOR_AUTOLOAD_DIR is set, in any platform, use it
-    // if not, if windows, use ALLUSERPROFILE\nushell\vendor\autoload
-    // if not, if non-windows, if env var PREFIX is set, use PREFIX/share/nushell/vendor/autoload
-    // if not, use the default /usr/share/nushell/vendor/autoload
+pub fn get_vendor_autoload_dirs(_engine_state: &EngineState) -> Vec<PathBuf> {
+    // load order for autoload dirs
+    // /Library/Application Support/nushell/vendor/autoload on macOS
+    // <dir>/nushell/vendor/autoload for every dir in XDG_DATA_DIRS in reverse order on platforms other than windows. If XDG_DATA_DIRS is not set, it falls back to <PREFIX>/share if PREFIX ends in local, or <PREFIX>/local/share:<PREFIX>/share otherwise. If PREFIX is not set, fall back to /usr/local/share:/usr/share.
+    // %ProgramData%\nushell\vendor\autoload on windows
+    // NU_VENDOR_AUTOLOAD_DIR from compile time, if env var is set at compile time
+    // if on macOS, additionally check XDG_DATA_HOME, which `dirs` is only doing on Linux
+    // <data_dir>/nushell/vendor/autoload of the current user according to the `dirs` crate
+    // NU_VENDOR_AUTOLOAD_DIR at runtime, if env var is set
 
-    // check to see if NU_VENDOR_AUTOLOAD_DIR env var is set, if not, use the default
-    Some(
-        option_env!("NU_VENDOR_AUTOLOAD_DIR")
-            .map(String::from)
-            .unwrap_or_else(|| {
-                if cfg!(windows) {
-                    let all_user_profile = match engine_state.get_env_var("ALLUSERPROFILE") {
-                        Some(v) => format!(
-                            "{}\\nushell\\vendor\\autoload",
-                            v.coerce_string().unwrap_or("C:\\ProgramData".into())
-                        ),
-                        None => "C:\\ProgramData\\nushell\\vendor\\autoload".into(),
-                    };
-                    all_user_profile
-                } else {
-                    // In non-Windows environments, if NU_VENDOR_AUTOLOAD_DIR is not set
-                    // check to see if PREFIX env var is set, and use it as PREFIX/nushell/vendor/autoload
-                    // otherwise default to /usr/share/nushell/vendor/autoload
-                    option_env!("PREFIX").map(String::from).map_or_else(
-                        || "/usr/local/share/nushell/vendor/autoload".into(),
-                        |prefix| format!("{}/share/nushell/vendor/autoload", prefix),
-                    )
-                }
+    let into_autoload_path_fn = |mut path: PathBuf| {
+        path.push("nushell");
+        path.push("vendor");
+        path.push("autoload");
+        path
+    };
+
+    let mut dirs = Vec::new();
+
+    let mut append_fn = |path: PathBuf| {
+        if !dirs.contains(&path) {
+            dirs.push(path)
+        }
+    };
+
+    #[cfg(target_os = "macos")]
+    std::iter::once("/Library/Application Support")
+        .map(PathBuf::from)
+        .map(into_autoload_path_fn)
+        .for_each(&mut append_fn);
+    #[cfg(unix)]
+    {
+        use std::os::unix::ffi::OsStrExt;
+
+        std::env::var_os("XDG_DATA_DIRS")
+            .or_else(|| {
+                option_env!("PREFIX").map(|prefix| {
+                    if prefix.ends_with("local") {
+                        std::ffi::OsString::from(format!("{prefix}/share"))
+                    } else {
+                        std::ffi::OsString::from(format!("{prefix}/local/share:{prefix}/share"))
+                    }
+                })
             })
-            .into(),
-    )
+            .unwrap_or_else(|| std::ffi::OsString::from("/usr/local/share/:/usr/share/"))
+            .as_encoded_bytes()
+            .split(|b| *b == b':')
+            .map(|split| into_autoload_path_fn(PathBuf::from(std::ffi::OsStr::from_bytes(split))))
+            .rev()
+            .for_each(&mut append_fn);
+    }
+
+    #[cfg(target_os = "windows")]
+    dirs_sys::known_folder(windows_sys::Win32::UI::Shell::FOLDERID_ProgramData)
+        .into_iter()
+        .map(into_autoload_path_fn)
+        .for_each(&mut append_fn);
+
+    option_env!("NU_VENDOR_AUTOLOAD_DIR")
+        .into_iter()
+        .map(PathBuf::from)
+        .for_each(&mut append_fn);
+
+    #[cfg(target_os = "macos")]
+    std::env::var("XDG_DATA_HOME")
+        .ok()
+        .map(PathBuf::from)
+        .or_else(|| {
+            dirs::home_dir().map(|mut home| {
+                home.push(".local");
+                home.push("share");
+                home
+            })
+        })
+        .map(into_autoload_path_fn)
+        .into_iter()
+        .for_each(&mut append_fn);
+
+    dirs::data_dir()
+        .into_iter()
+        .map(into_autoload_path_fn)
+        .for_each(&mut append_fn);
+
+    std::env::var_os("NU_VENDOR_AUTOLOAD_DIR")
+        .into_iter()
+        .map(PathBuf::from)
+        .for_each(&mut append_fn);
+
+    dirs
 }
 
 fn eval_const_call(

src/config_files.rs

@@ -200,8 +200,7 @@ pub(crate) fn read_vendor_autoload_files(engine_state: &mut EngineState, stack:
         column!()
     );
 
-    // read and source vendor_autoload_files file if exists
-    if let Some(autoload_dir) = nu_protocol::eval_const::get_vendor_autoload_dir(engine_state) {
+    for autoload_dir in nu_protocol::eval_const::get_vendor_autoload_dirs(engine_state) {
         warn!("read_vendor_autoload_files: {}", autoload_dir.display());
 
         if autoload_dir.exists() {