Fix PackageManager reset

Author: silvanocerza

arduino/cores/packagemanager/package_manager.go

@@ -65,8 +65,7 @@ func NewPackageManager(indexDir, packagesDir, downloadDir, tempDir *paths.Path)
 func (pm *PackageManager) Clear() {
 	pm.Packages = cores.NewPackages()
 	pm.CustomGlobalProperties = properties.NewMap()
-	pm.discoveryManager.StopAll()
-	pm.discoveryManager = discoverymanager.New()
+	pm.discoveryManager.Clear()
 }
 
 // DiscoveryManager returns the DiscoveryManager in use by this PackageManager

arduino/cores/packagemanager/package_manager_test.go

@@ -332,12 +332,12 @@ func TestPackageManagerClear(t *testing.T) {
 	emptyPackageManager := packagemanager.NewPackageManager(customHardware, customHardware, customHardware, customHardware)
 
 	// Verifies they're not equal
-	require.NotEqual(t, &packageManager, &emptyPackageManager)
+	require.NotEqual(t, packageManager, emptyPackageManager)
 
 	// Clear the first PackageManager that contains loaded hardware
 	packageManager.Clear()
 	// Verifies both PackageManagers are now equal
-	require.Equal(t, &packageManager, &emptyPackageManager)
+	require.Equal(t, packageManager, emptyPackageManager)
 }
 
 func TestFindToolsRequiredFromPlatformRelease(t *testing.T) {

arduino/discovery/discoverymanager/discoverymanager.go

@@ -31,10 +31,17 @@ type DiscoveryManager struct {
 func New() *DiscoveryManager {
 	return &DiscoveryManager{
 		discoveries:   map[string]*discovery.PluggableDiscovery{},
-		globalEventCh: make(chan *discovery.Event, 5),
+		globalEventCh: nil,
 	}
 }
 
+// Clear resets the DiscoveryManager to its initial state
+func (dm *DiscoveryManager) Clear() {
+	dm.QuitAll()
+	dm.discoveries = map[string]*discovery.PluggableDiscovery{}
+	dm.globalEventCh = nil
+}
+
 // IDs returns the list of discoveries' ids in this DiscoveryManager
 func (dm *DiscoveryManager) IDs() []string {
 	ids := []string{}