Show information about updated plugin during update command

cmd/krew/cmd/update.go

@@ -17,15 +17,30 @@ package cmd
 import (
 	"fmt"
 	"os"
+	"sort"
 
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 	"k8s.io/klog"
 
 	"sigs.k8s.io/krew/internal/gitutil"
+	"sigs.k8s.io/krew/internal/index/indexscanner"
+	"sigs.k8s.io/krew/internal/installation"
 	"sigs.k8s.io/krew/pkg/constants"
 )
 
+type newPlugin struct {
+	name    string
+	version string
+}
+
+type newVersionPlugin struct {
+	name       string
+	installed  bool
+	oldVersion string
+	newVersion string
+}
+
 // updateCmd represents the update command
 var updateCmd = &cobra.Command{
 	Use:   "update",
@@ -41,12 +56,124 @@ Remarks:
 	RunE: ensureIndexUpdated,
 }
 
+func retrievePluginNameVersionMap() (map[string]string, error) {
+	plugins, err := indexscanner.LoadPluginListFromFS(paths.IndexPluginsPath())
+	if err != nil {
+		return map[string]string{}, err
+	}
+
+	m := make(map[string]string, len(plugins))
+	for _, p := range plugins {
+		m[p.Name] = p.Spec.Version
+	}
+
+	return m, nil
+}
+
+func retrieveInstalledPluginMap() (map[string]bool, error) {
+	plugins, err := installation.ListInstalledPlugins(paths.InstallReceiptsPath())
+	if err != nil {
+		return map[string]bool{}, err
+	}
+	m := make(map[string]bool, len(plugins))
+	for name := range plugins {
+		m[name] = true
+	}
+
+	return m, nil
+}
+
+func filterAndSortUpdatedPlugins(old, updated map[string]string, installed map[string]bool) ([]newPlugin, []newVersionPlugin) {
+	var newPluginList []newPlugin
+	var newVersionList []newVersionPlugin
+
+	for name, version := range updated {
+		oldVersion, ok := old[name]
+		if !ok {
+			newPluginList = append(newPluginList, newPlugin{
+				name:    name,
+				version: version,
+			})
+			continue
+		}
+
+		if version != oldVersion {
+			_, installed := installed[name]
+			newVersionList = append(newVersionList, newVersionPlugin{
+				name:       name,
+				installed:  installed,
+				oldVersion: oldVersion,
+				newVersion: version,
+			})
+			continue
+		}
+	}
+
+	sort.Slice(newPluginList, func(i, j int) bool {
+		return newPluginList[i].name < newPluginList[j].name
+	})
+
+	sort.Slice(newVersionList, func(i, j int) bool {
+		if newVersionList[i].installed && !newVersionList[j].installed {
+			return true
+		}
+
+		if !newVersionList[i].installed && newVersionList[j].installed {
+			return false
+		}
+
+		return newVersionList[i].name < newVersionList[j].name
+	})
+
+	return newPluginList, newVersionList
+}
+
+func showUpdatedPlugins(newPluginList []newPlugin, newVersionList []newVersionPlugin) {
+	if len(newPluginList) > 0 {
+		fmt.Fprintln(os.Stderr, "  New plugins available:")
+		for _, np := range newPluginList {
+			fmt.Fprintf(os.Stderr, "    * %s %s\n", np.name, np.version)
+		}
+	}
+
+	if len(newVersionList) > 0 {
+		fmt.Fprintln(os.Stderr, "  The following plugins have new version:")
+		for _, np := range newVersionList {
+			if np.installed {
+				fmt.Fprintf(os.Stderr, "    * %s %s -> %s (!)\n", np.name, np.oldVersion, np.newVersion)
+				continue
+			}
+			fmt.Fprintf(os.Stderr, "    * %s %s -> %s\n", np.name, np.oldVersion, np.newVersion)
+		}
+	}
+}
+
 func ensureIndexUpdated(_ *cobra.Command, _ []string) error {
+	oldMap, err := retrievePluginNameVersionMap()
+	if err != nil {
+		return errors.Wrap(err, "failed to load the list of plugins from the index")
+	}
+
 	klog.V(1).Infof("Updating the local copy of plugin index (%s)", paths.IndexPath())
 	if err := gitutil.EnsureUpdated(constants.IndexURI, paths.IndexPath()); err != nil {
 		return errors.Wrap(err, "failed to update the local index")
 	}
 	fmt.Fprintln(os.Stderr, "Updated the local copy of plugin index.")
+
+	updatedMap, err := retrievePluginNameVersionMap()
+	if err != nil {
+		return errors.Wrap(err, "failed to load the list of plugins from the index")
+	}
+
+	installedMap, err := retrieveInstalledPluginMap()
+	if err != nil {
+		return errors.Wrap(err, "failed to find all installed versions")
+	}
+
+	newPluginList, newVersionList := filterAndSortUpdatedPlugins(oldMap, updatedMap, installedMap)
+
+	showUpdatedPlugins(newPluginList, newVersionList)
+
 	return nil
 }