enabling logging module only when tracing-subscriber is enabled

src/lib.rs

@@ -164,7 +164,6 @@ extern crate core;
 
 pub mod base;
 pub mod dep;
-mod logging;
 pub mod net;
 pub mod rdata;
 pub mod resolv;
@@ -176,3 +175,5 @@ pub mod validate;
 pub mod validator;
 pub mod zonefile;
 pub mod zonetree;
+
+mod logging;

src/logging.rs

@@ -1,18 +1,16 @@
-use tracing_subscriber::EnvFilter;
+//! Common logging functions
 
 /// Setup logging of events reported by domain and the test suite.
 ///
 /// Use the RUST_LOG environment variable to override the defaults.
 ///
 /// E.g. To enable debug level logging:
-///   RUST_LOG=DEBUG
-///
-/// Or to log only the steps processed by the Stelline client:
-///   RUST_LOG=net_server::net::stelline::client=DEBUG
-///
-/// Or to enable trace level logging but not for the test suite itself:
-///   RUST_LOG=TRACE,net_server=OFF
+/// ```
+/// RUST_LOG=DEBUG
+/// ```
+#[cfg(feature = "tracing-subscriber")]
 pub fn init_logging() {
+    use tracing_subscriber::EnvFilter;
     tracing_subscriber::fmt()
         .with_env_filter(EnvFilter::from_default_env())
         .with_thread_ids(true)