Directly read preferences instead of using the defaults CLI

CHANGELOG.md

@@ -13,6 +13,7 @@
 
 - Various bash completion improvements, see #2310 (@scop)
 - Disable completion of `cache` subcommand, see #2399 (@cyqsimon)
+- Signifigantly improve startup performance on macOS, see #2442 (@BlackHoleFox)
 
 ## Syntaxes
 

Cargo.lock

@@ -97,6 +97,7 @@ dependencies = [
  "nix",
  "once_cell",
  "path_abs",
+ "plist",
  "predicates",
  "regex",
  "semver",

Cargo.toml

@@ -81,6 +81,10 @@ version = "4.0.2"
 optional = true
 features = ["wrap_help", "cargo"]
 
+[target.'cfg(target_os = "macos")'.dependencies]
+dirs-next = "2.0.0"
+plist = "1.3"
+
 [dev-dependencies]
 assert_cmd = "2.0.8"
 expect-test = "1.4.0"

src/assets.rs

@@ -401,11 +401,21 @@ fn asset_from_cache<T: serde::de::DeserializeOwned>(
 
 #[cfg(target_os = "macos")]
 fn macos_dark_mode_active() -> bool {
-    let mut defaults_cmd = std::process::Command::new("defaults");
-    defaults_cmd.args(&["read", "-globalDomain", "AppleInterfaceStyle"]);
-    match defaults_cmd.output() {
-        Ok(output) => output.stdout == b"Dark\n",
-        Err(_) => true,
+    const PREFERENCES_FILE: &str = "Library/Preferences/.GlobalPreferences.plist";
+    const STYLE_KEY: &str = "AppleInterfaceStyle";
+
+    let preferences_file = dirs_next::home_dir()
+        .map(|home| home.join(PREFERENCES_FILE))
+        .expect("Could not get home directory");
+
+    match plist::Value::from_file(preferences_file).map(|file| file.into_dictionary()) {
+        Ok(Some(preferences)) => match preferences.get(STYLE_KEY).and_then(|val| val.as_string()) {
+            Some(value) => value == "Dark",
+            // If the key does not exist, then light theme is currently in use.
+            None => false,
+        },
+        // Unreachable, in theory. All macOS users have a home directory and preferences file setup.
+        Ok(None) | Err(_) => true,
     }
 }