[cli-dev-mode] complete state subjects when shutting down (#96003)

Co-authored-by: spalger <spalger@users.noreply.github.com>

packages/kbn-cli-dev-mode/src/dev_server.ts

@@ -249,5 +249,11 @@ export class DevServer {
         )
         .subscribe(subscriber)
     );
+
+    // complete state subjects when run$ completes
+    subscriber.add(() => {
+      this.phase$.complete();
+      this.ready$.complete();
+    });
   });
 }

packages/kbn-cli-dev-mode/src/optimizer.test.ts

@@ -180,6 +180,7 @@ it('is ready when optimizer phase is success or issue and logs in familiar forma
       "ready: false",
       "<issue>",
       "ready: true",
+      "complete",
     ]
   `);
 

packages/kbn-cli-dev-mode/src/optimizer.ts

@@ -107,14 +107,26 @@ export class Optimizer {
       },
     ]);
 
-    this.run$ = runOptimizer(config).pipe(
-      logOptimizerState(log, config),
-      tap(({ state }) => {
-        this.phase$.next(state.phase);
-        this.ready$.next(state.phase === 'success' || state.phase === 'issue');
-      }),
-      ignoreElements()
-    );
+    this.run$ = new Rx.Observable<void>((subscriber) => {
+      subscriber.add(
+        runOptimizer(config)
+          .pipe(
+            logOptimizerState(log, config),
+            tap(({ state }) => {
+              this.phase$.next(state.phase);
+              this.ready$.next(state.phase === 'success' || state.phase === 'issue');
+            }),
+            ignoreElements()
+          )
+          .subscribe(subscriber)
+      );
+
+      // complete state subjects when run$ completes
+      subscriber.add(() => {
+        this.phase$.complete();
+        this.ready$.complete();
+      });
+    });
   }
 
   getPhase$() {

packages/kbn-cli-dev-mode/src/watcher.ts

@@ -103,6 +103,11 @@ export class Watcher {
         .pipe(ignoreElements())
         .subscribe(subscriber)
     );
+
+    // complete state subjects when run$ completes
+    subscriber.add(() => {
+      this.restart$.complete();
+    });
   });
 
   serverShouldRestart$() {