Extend listener removal in BusHelper (#37)

* Extend listener removal in BusHelper

- Adds a clean-up function `removeListeners` that in addition to
  the already existing PropertiesChanged removal on itself
  (in `Device.disconnect`) also removes PropertiesChanged
  event listeners on the _propsProxy object.
- Adds use of this clean-up function in `Device.disconnect`.

* Fix re-use after listener removal in BusHelper

* Add test cases for BusHelper.removeListeners

src/BusHelper.js

@@ -97,6 +97,14 @@ class BusHelper extends EventEmitter {
     return this._ifaceProxy[methodName](...args)
   }
 
+  removeListeners () {
+    this.removeAllListeners('PropertiesChanged')
+    if (this._propsProxy !== null) {
+      this._propsProxy.removeAllListeners('PropertiesChanged')
+      this._ready = false
+    }
+  }
+
   static buildChildren (path, nodes) {
     if (path === '/') path = ''
     const children = new Set()

src/Device.js

@@ -119,7 +119,7 @@ class Device extends EventEmitter {
    */
   async disconnect () {
     await this.helper.callMethod('Disconnect')
-    this.helper.removeAllListeners('PropertiesChanged') // might be improved
+    this.helper.removeListeners()
   }
 
   /**

test/BusHelper.spec.js

@@ -125,3 +125,31 @@ test('propsEvents', async () => {
   await helper.set('VirtualProperty', buildTypedValue('string', 'bar'))
   await expect(res).resolves.toMatchObject({ VirtualProperty: { signature: 's', value: 'bar' } })
 })
+
+test('removeListeners', async () => {
+  const helper = new BusHelper(dbus, TEST_NAME, TEST_OBJECT, TEST_IFACE, { useProps: true, usePropsEvents: true })
+
+  const dummyCb = () => {}
+
+  // Init with listener on helper (directly attached dummyCb) and _propsProxy (through method call triggered _prepare)
+  helper.on('PropertiesChanged', dummyCb)
+  await helper.callMethod('Echo', 'ping')
+  expect(helper.listenerCount('PropertiesChanged')).toBeGreaterThan(0)
+  expect(helper._propsProxy.listenerCount('PropertiesChanged')).toBeGreaterThan(0)
+
+  // Test remove
+  helper.removeListeners()
+  expect(helper.listenerCount('PropertiesChanged')).toBe(0)
+  expect(helper._propsProxy.listenerCount('PropertiesChanged')).toBe(0)
+
+  // Test reuse after remove (same initialization as before)
+  helper.on('PropertiesChanged', dummyCb)
+  await helper.callMethod('Echo', 'ping')
+  expect(helper.listenerCount('PropertiesChanged')).toBeGreaterThan(0)
+  expect(helper._propsProxy.listenerCount('PropertiesChanged')).toBeGreaterThan(0)
+
+  // Remove second time
+  helper.removeListeners()
+  expect(helper.listenerCount('PropertiesChanged')).toBe(0)
+  expect(helper._propsProxy.listenerCount('PropertiesChanged')).toBe(0)
+})

test/Device.spec.js

@@ -13,6 +13,7 @@ jest.doMock('../src/BusHelper', () => {
       this.waitPropChange = jest.fn()
       this.children = jest.fn()
       this.callMethod = jest.fn()
+      this.removeListeners = jest.fn()
     }
   }
 })