Plugins: Perform plugin update check prior to uninstall (#36909)

* only uninstall if update is possible

* add .

* update lingo for clarity

pkg/plugins/manager/installer/installer.go

@@ -410,9 +410,28 @@ func normalizeVersion(version string) string {
 	return normalized
 }
 
-// selectVersion returns latest version if none is specified or the specified version. If the version string is not
-// matched to existing version it errors out. It also errors out if version that is matched is not available for current
-// os and platform. It expects plugin.Versions to be sorted so the newest version is first.
+func (i *Installer) GetUpdateInfo(pluginID, version, pluginRepoURL string) (plugins.UpdateInfo, error) {
+	plugin, err := i.getPluginMetadataFromPluginRepo(pluginID, pluginRepoURL)
+	if err != nil {
+		return plugins.UpdateInfo{}, err
+	}
+
+	v, err := i.selectVersion(&plugin, version)
+	if err != nil {
+		return plugins.UpdateInfo{}, err
+	}
+
+	return plugins.UpdateInfo{
+		PluginZipURL: fmt.Sprintf("%s/%s/versions/%s/download", pluginRepoURL, pluginID, v.Version),
+	}, nil
+}
+
+// selectVersion selects the most appropriate plugin version
+// returns the specified version if supported.
+// returns latest version if no specific version is specified.
+// returns error if the supplied version does not exist.
+// returns error if supplied version exists but is not supported.
+// NOTE: It expects plugin.Versions to be sorted so the newest version is first.
 func (i *Installer) selectVersion(plugin *Plugin, version string) (*Version, error) {
 	var ver Version
 

pkg/plugins/manager/manager.go

@@ -726,6 +726,8 @@ func (pm *PluginManager) StaticRoutes() []*plugins.PluginStaticRoute {
 
 func (pm *PluginManager) Install(ctx context.Context, pluginID, version string) error {
 	plugin := pm.GetPlugin(pluginID)
+
+	var pluginZipURL string
 	if plugin != nil {
 		if plugin.IsCorePlugin {
 			return plugins.ErrInstallCorePlugin
@@ -738,14 +740,22 @@ func (pm *PluginManager) Install(ctx context.Context, pluginID, version string)
 			}
 		}
 
+		// get plugin update information to confirm if upgrading is possible
+		updateInfo, err := pm.pluginInstaller.GetUpdateInfo(pluginID, version, grafanaComURL)
+		if err != nil {
+			return err
+		}
+
+		pluginZipURL = updateInfo.PluginZipURL
+
 		// remove existing installation of plugin
-		err := pm.Uninstall(context.Background(), plugin.Id)
+		err = pm.Uninstall(context.Background(), plugin.Id)
 		if err != nil {
 			return err
 		}
 	}
 
-	err := pm.pluginInstaller.Install(ctx, pluginID, version, pm.Cfg.PluginsPath, "", grafanaComURL)
+	err := pm.pluginInstaller.Install(ctx, pluginID, version, pm.Cfg.PluginsPath, pluginZipURL, grafanaComURL)
 	if err != nil {
 		return err
 	}

pkg/plugins/manager/manager_test.go

@@ -702,6 +702,10 @@ func (f *fakePluginInstaller) Uninstall(ctx context.Context, pluginPath string)
 	return nil
 }
 
+func (f *fakePluginInstaller) GetUpdateInfo(pluginID, version, pluginRepoURL string) (plugins.UpdateInfo, error) {
+	return plugins.UpdateInfo{}, nil
+}
+
 func createManager(t *testing.T, cbs ...func(*PluginManager)) *PluginManager {
 	t.Helper()