Prevent restarting a startableStoppable when already being started

Co-authored-by: Mikko Aspiala <mikko.aspiala@gmail.com>

Signed-off-by: Janne Savolainen <janne.savolainen@live.fi>

src/common/utils/get-startable-stoppable.test.ts

@@ -57,6 +57,24 @@ describe("getStartableStoppable", () => {
       expect(actual.started).toBe(false);
     });
 
+    describe("when started again before the start has finished", () => {
+      let error: Error;
+
+      beforeEach(() => {
+        startMock.mockClear();
+
+        actual.start().catch((e) => { error = e; });
+      });
+
+      it("does not start starting again", () => {
+        expect(startMock).not.toHaveBeenCalled();
+      });
+
+      it("throws", () => {
+        expect(error.message).toBe("Tried to start \"some-id\", but it is already being started.");
+      });
+    });
+
     describe("when starting finishes", () => {
       beforeEach(async () => {
         await startMock.resolve(stopMock);

src/common/utils/get-startable-stoppable.ts

@@ -13,6 +13,7 @@ export const getStartableStoppable = (
   let stop: Stopper;
   let stopped = false;
   let started = false;
+  let starting = false;
   let startingPromise: Promise<Stopper> | Stopper;
 
   return {
@@ -21,6 +22,12 @@ export const getStartableStoppable = (
     },
 
     start: async () => {
+      if (starting) {
+        throw new Error(`Tried to start "${id}", but it is already being started.`);
+      }
+
+      starting = true;
+
       if (started) {
         throw new Error(`Tried to start "${id}", but it has already started.`);
       }
@@ -30,6 +37,7 @@ export const getStartableStoppable = (
 
       stopped = false;
       started = true;
+      starting = false;
     },
 
     stop: async () => {