fix: prevent instrumentation to run in test mode (#102)

The CI pipeline (`./check.sh`) was failing because of test errors, which was caused by the instrumentation framework complaining that no subscribers/listeners were registered.

Instead of setting up all tests to run with a dummy subscriber, move the implementation of the instrumentation behind a feature flag so that it runs only for tests.

There's a catch though: the `#[cfg(test)]` directive works only when directly testing the crate. If a crate `A` depends on another crate `B`, `B` will be compiled as usual (aka not in test mode) which will not trigger the `test` flag.

So we need to introduce our own `testing` feature flag for `harmony` core and import it with that flag (only during dev/test).

More info: https://github.com/rust-lang/rust/issues/59168

Co-authored-by: Ian Letourneau <letourneau.ian@gmail.com>
Reviewed-on: https://git.nationtech.io/NationTech/harmony/pulls/102

harmony/Cargo.toml

@@ -5,6 +5,9 @@ version.workspace = true
 readme.workspace = true
 license.workspace = true
 
+[features]
+testing = []
+
 [dependencies]
 rand = "0.9"
 hex = "0.4"

harmony/src/domain/instrumentation.rs

@@ -36,9 +36,14 @@ static HARMONY_EVENT_BUS: Lazy<broadcast::Sender<HarmonyEvent>> = Lazy::new(|| {
 });
 
 pub fn instrument(event: HarmonyEvent) -> Result<(), &'static str> {
-    match HARMONY_EVENT_BUS.send(event) {
-        Ok(_) => Ok(()),
-        Err(_) => Err("send error: no subscribers"),
+    if cfg!(any(test, feature = "testing")) {
+        let _ = event; // Suppress the "unused variable" warning for `event`
+        Ok(())
+    } else {
+        match HARMONY_EVENT_BUS.send(event) {
+            Ok(_) => Ok(()),
+            Err(_) => Err("send error: no subscribers"),
+        }
     }
 }
 

harmony/src/modules/k3d/install.rs

@@ -7,7 +7,6 @@ use serde::Serialize;
 use crate::{
     config::HARMONY_DATA_DIR,
     data::{Id, Version},
-    instrumentation::{self, HarmonyEvent},
     interpret::{Interpret, InterpretError, InterpretName, InterpretStatus, Outcome},
     inventory::Inventory,
     score::Score,
@@ -30,7 +29,7 @@ impl Default for K3DInstallationScore {
 }
 
 impl<T: Topology> Score<T> for K3DInstallationScore {
-    fn create_interpret(&self) -> Box<dyn crate::interpret::Interpret<T>> {
+    fn create_interpret(&self) -> Box<dyn Interpret<T>> {
         Box::new(K3dInstallationInterpret {
             score: self.clone(),
         })