Add systemd feature flag for systemd-specific things

Cargo.toml

@@ -97,9 +97,11 @@ proptest-derive = "0.4.0"
 xshell = "0.2.5"
 
 [features]
-default = ["dbus", "xdp-gnome-screencast"]
+default = ["dbus", "systemd", "xdp-gnome-screencast"]
-# Enables DBus support (required for xdp-gnome and power button inhibiting).
+# Enables D-Bus support (serve various freedesktop and GNOME interfaces, power button handling).
 dbus = ["zbus", "async-channel", "async-io", "notify-rust", "url"]
+# Enables systemd integration (global environment, apps in transient scopes).
+systemd = ["dbus"]
 # Enables screencasting support through xdg-desktop-portal-gnome.
 xdp-gnome-screencast = ["dbus", "pipewire"]
 # Enables the Tracy profiler instrumentation.

src/main.rs

@@ -38,7 +38,15 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         REMOVE_ENV_RUST_LIB_BACKTRACE.store(true, Ordering::Relaxed);
     }
 
-    IS_SYSTEMD_SERVICE.store(env::var_os("NOTIFY_SOCKET").is_some(), Ordering::Relaxed);
+    if env::var_os("NOTIFY_SOCKET").is_some() {
+        IS_SYSTEMD_SERVICE.store(true, Ordering::Relaxed);
+
+        #[cfg(not(feature = "systemd"))]
+        warn!(
+            "running as a systemd service, but systemd support is compiled out. \
+             Are you sure you did not forget to set `--features systemd`?"
+        );
+    }
 
     let directives = env::var("RUST_LOG").unwrap_or_else(|_| "niri=debug".to_owned());
     let env_filter = EnvFilter::builder().parse_lossy(directives);
@@ -249,11 +257,16 @@ fn import_environment() {
     ]
     .join(" ");
 
+    #[cfg(feature = "systemd")]
+    let systemctl = format!("systemctl --user import-environment {variables} && ");
+    #[cfg(not(feature = "systemd"))]
+    let systemctl = String::new();
+
     let rv = Command::new("/bin/sh")
         .args([
             "-c",
             &format!(
-                "systemctl --user import-environment {variables} && \
+                "{systemctl}\
                  hash dbus-update-activation-environment 2>/dev/null && \
                  dbus-update-activation-environment {variables}"
             ),
@@ -273,7 +286,7 @@ fn import_environment() {
             }
         },
         Err(err) => {
-            warn!("error spawning shell to import environment into systemd: {err:?}");
+            warn!("error spawning shell to import environment: {err:?}");
         }
     }
 }

src/niri.rs

@@ -1063,8 +1063,6 @@ impl Niri {
     pub fn inhibit_power_key(&mut self) -> anyhow::Result<()> {
         let conn = zbus::blocking::ConnectionBuilder::system()?.build()?;
 
-        // logind-zbus has a wrong signature for this method, so do it manually.
-        // https://gitlab.com/flukejones/logind-zbus/-/merge_requests/5
         let message = conn.call_method(
             Some("org.freedesktop.login1"),
             "/org/freedesktop/login1",

src/utils.rs

@@ -229,7 +229,7 @@ fn spawn_sync(command: impl AsRef<OsStr>, args: impl IntoIterator<Item = impl As
                 trace!("spawned PID: {pid}");
 
                 // Start a systemd scope for the grandchild.
-                #[cfg(feature = "dbus")]
+                #[cfg(feature = "systemd")]
                 if let Err(err) = start_systemd_scope(command, child.id(), pid as u32) {
                     trace!("error starting systemd scope for spawned command: {err:?}");
                 }
@@ -292,7 +292,7 @@ pub static IS_SYSTEMD_SERVICE: AtomicBool = AtomicBool::new(false);
 ///
 /// This separates the pid from the compositor scope, which for example prevents the OOM killer
 /// from bringing down the compositor together with a misbehaving client.
-#[cfg(feature = "dbus")]
+#[cfg(feature = "systemd")]
 fn start_systemd_scope(name: &OsStr, intermediate_pid: u32, child_pid: u32) -> anyhow::Result<()> {
     use std::fmt::Write as _;
     use std::path::Path;