krew info: Improve error message when plugin doesn't exist (kubernete…

…s-sigs#14)

* krew info: Improve error message when plugin doesn't exist

* fixup! krew info: Improve error message when plugin doesn't exist

cmd/krew/cmd/info.go

@@ -36,7 +36,9 @@ Use this command to find out about plugin requirements and caveats.`,
 	Run: func(cmd *cobra.Command, args []string) {
 		for _, arg := range args {
 			plugin, err := indexscanner.LoadPluginFileFromFS(paths.Index, arg)
-			if err != nil {
+			if os.IsNotExist(err) {
+				glog.Fatalf("plugin %q not found", arg)
+			} else if err != nil {
 				glog.Fatal(err)
 			}
 			printPluginInfo(os.Stdout, plugin)

pkg/index/indexscanner/scanner.go

@@ -64,7 +64,8 @@ func LoadPluginListFromFS(indexDir string) (index.PluginList, error) {
 	return indexList, nil
 }
 
-// LoadPluginFileFromFS loads a plugins index file by its name.
+// LoadPluginFileFromFS loads a plugins index file by its name. When plugin
+// file not found, it returns an error that can be checked with os.IsNotExist.
 func LoadPluginFileFromFS(indexDir, pluginName string) (index.Plugin, error) {
 	if !index.IsSafePluginName(pluginName) {
 		return index.Plugin{}, fmt.Errorf("plugin name %q not allowed", pluginName)
@@ -76,17 +77,22 @@ func LoadPluginFileFromFS(indexDir, pluginName string) (index.Plugin, error) {
 		return index.Plugin{}, err
 	}
 	p, err := ReadPluginFile(filepath.Join(indexDir, pluginName+".yaml"))
-	if err != nil {
+	if os.IsNotExist(err) {
+		return index.Plugin{}, err
+	} else if err != nil {
 		return index.Plugin{}, fmt.Errorf("failed to read the plugin file, err: %v", err)
 	}
 	return p, p.Validate(pluginName)
 }
 
-// ReadPluginFile loads a file from the FS
+// ReadPluginFile loads a file from the FS. When plugin file not found, it
+// returns an error that can be checked with os.IsNotExist.
 // TODO(lbb): Add object verification
 func ReadPluginFile(indexFilePath string) (index.Plugin, error) {
 	f, err := os.Open(indexFilePath)
-	if err != nil {
+	if os.IsNotExist(err) {
+		return index.Plugin{}, err
+	} else if err != nil {
 		return index.Plugin{}, fmt.Errorf("failed to open index file, err: %v", err)
 	}
 	return DecodePluginFile(f)

pkg/index/indexscanner/scanner_test.go

@@ -15,6 +15,7 @@
 package indexscanner
 
 import (
+	"os"
 	"path/filepath"
 	"testing"
 
@@ -125,33 +126,37 @@ func TestLoadIndexFileFromFS(t *testing.T) {
 		pluginName string
 	}
 	tests := []struct {
-		name    string
-		args    args
-		wantErr bool
+		name              string
+		args              args
+		wantErr           bool
+		wantIsNotExistErr bool
 	}{
 		{
 			name: "load single index file",
 			args: args{
 				indexDir:   filepath.Join(testdataPath(t), "testindex"),
 				pluginName: "foo",
 			},
-			wantErr: false,
+			wantErr:           false,
+			wantIsNotExistErr: false,
 		},
 		{
 			name: "plugin file not found",
 			args: args{
 				indexDir:   filepath.FromSlash("./testdata"),
 				pluginName: "not",
 			},
-			wantErr: true,
+			wantErr:           true,
+			wantIsNotExistErr: true,
 		},
 		{
 			name: "plugin file bad name",
 			args: args{
 				indexDir:   filepath.FromSlash("./testdata"),
 				pluginName: "wrongname",
 			},
-			wantErr: true,
+			wantErr:           true,
+			wantIsNotExistErr: true,
 		},
 	}
 	for _, tt := range tests {
@@ -161,6 +166,10 @@ func TestLoadIndexFileFromFS(t *testing.T) {
 				t.Errorf("LoadIndexFileFromFS() got = %##v,error = %v, wantErr %v", got, err, tt.wantErr)
 				return
 			}
+			if os.IsNotExist(err) != tt.wantIsNotExistErr {
+				t.Errorf("LoadIndexFileFromFS() got = %##v,error = %v, wantIsNotExistErr %v", got, err, tt.wantErr)
+				return
+			}
 		})
 	}
 }