Compute bucket and mountpoint for cobra command

This adds the logic to compute the bucket and mountpoint for cobra root
command.

cmd/legacy_main.go

@@ -177,19 +177,19 @@ func mountWithArgs(
 	return
 }
 
-func populateArgs(c *cli.Context) (
+func populateArgs(args []string) (
 	bucketName string,
 	mountPoint string,
 	err error) {
 	// Extract arguments.
-	switch len(c.Args()) {
+	switch len(args) {
 	case 1:
 		bucketName = ""
-		mountPoint = c.Args()[0]
+		mountPoint = args[0]
 
 	case 2:
-		bucketName = c.Args()[0]
-		mountPoint = c.Args()[1]
+		bucketName = args[0]
+		mountPoint = args[1]
 
 	default:
 		err = fmt.Errorf(
@@ -284,7 +284,7 @@ func runCLIApp(c *cli.Context) (err error) {
 
 	var bucketName string
 	var mountPoint string
-	bucketName, mountPoint, err = populateArgs(c)
+	bucketName, mountPoint, err = populateArgs(c.Args())
 	if err != nil {
 		return
 	}

cmd/root.go

@@ -26,7 +26,7 @@ import (
 )
 
 // NewRootCmd accepts the mountFn that it executes with the parsed configuration
-func NewRootCmd(mountFn func(config cfg.Config) error) (*cobra.Command, error) {
+func NewRootCmd(mountFn func(*cfg.Config, string, string) error) (*cobra.Command, error) {
 	var (
 		configObj cfg.Config
 		cfgFile   string
@@ -45,7 +45,11 @@ of Cloud Storage FUSE, see https://cloud.google.com/storage/docs/gcs-fuse.`,
 			if cfgErr != nil {
 				return fmt.Errorf("error while parsing config: %w", cfgErr)
 			}
-			return mountFn(configObj)
+			if bucket, mountpoint, err := populateArgs(args[1:]); err != nil {
+				return fmt.Errorf("error occurred while extracting the bucket and mountpoint: %w", err)
+			} else {
+				return mountFn(&configObj, bucket, mountpoint)
+			}
 		},
 	}
 	initConfig := func() {

cmd/root_test.go

@@ -15,6 +15,8 @@
 package cmd
 
 import (
+	"os"
+	"path"
 	"testing"
 
 	"github.com/googlecloudplatform/gcsfuse/v2/cfg"
@@ -24,7 +26,7 @@ import (
 )
 
 func TestInvalidConfig(t *testing.T) {
-	cmd, err := NewRootCmd(func(config cfg.Config) error { return nil })
+	cmd, err := NewRootCmd(func(*cfg.Config, string, string) error { return nil })
 	if err != nil {
 		t.Fatalf("Error while creating the root command: %v", err)
 	}
@@ -39,7 +41,7 @@ func TestInvalidConfig(t *testing.T) {
 }
 
 func TestValidConfig(t *testing.T) {
-	cmd, err := NewRootCmd(func(config cfg.Config) error { return nil })
+	cmd, err := NewRootCmd(func(*cfg.Config, string, string) error { return nil })
 	if err != nil {
 		t.Fatalf("Error while creating the root command: %v", err)
 	}
@@ -49,8 +51,8 @@ func TestValidConfig(t *testing.T) {
 }
 
 func TestDefaultMaxParallelDownloads(t *testing.T) {
-	var actual cfg.Config
-	cmd, err := NewRootCmd(func(c cfg.Config) error {
+	var actual *cfg.Config
+	cmd, err := NewRootCmd(func(c *cfg.Config, _, _ string) error {
 		actual = c
 		return nil
 	})
@@ -92,7 +94,7 @@ func TestCobraArgsNumInRange(t *testing.T) {
 
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
-			cmd, err := NewRootCmd(func(config cfg.Config) error { return nil })
+			cmd, err := NewRootCmd(func(*cfg.Config, string, string) error { return nil })
 			require.Nil(t, err)
 			cmd.SetArgs(tc.args)
 
@@ -106,3 +108,63 @@ func TestCobraArgsNumInRange(t *testing.T) {
 		})
 	}
 }
+
+func TestArgsParsing(t *testing.T) {
+	wd, err := os.Getwd()
+	require.Nil(t, err)
+	hd, err := os.UserHomeDir()
+	require.Nil(t, err)
+	tests := []struct {
+		name               string
+		args               []string
+		expectedBucket     string
+		expectedMountpoint string
+	}{
+		{
+			name:               "Both bucket and mountpoint specified.",
+			args:               []string{"gcsfuse", "abc", "pqr"},
+			expectedBucket:     "abc",
+			expectedMountpoint: path.Join(wd, "pqr"),
+		},
+		{
+			name:               "Only mountpoint specified",
+			args:               []string{"gcsfuse", "pqr"},
+			expectedBucket:     "",
+			expectedMountpoint: path.Join(wd, "pqr"),
+		},
+		{
+			name:               "Absolute path for mountpoint specified",
+			args:               []string{"gcsfuse", "/pqr"},
+			expectedBucket:     "",
+			expectedMountpoint: "/pqr",
+		},
+		{
+			name:               "Relative path from user's home specified as mountpoint",
+			args:               []string{"gcsfuse", "~/pqr"},
+			expectedBucket:     "",
+			expectedMountpoint: path.Join(hd, "pqr"),
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			var bucketName, mountPoint string
+			cmd, err := NewRootCmd(func(_ *cfg.Config, b string, m string) error {
+				bucketName = b
+				mountPoint = m
+				return nil
+			})
+			require.Nil(t, err)
+			cmd.SetArgs(tc.args)
+
+			err = cmd.Execute()
+
+			if assert.Nil(t, err) {
+				assert.Equal(t, tc.expectedBucket, bucketName)
+				if assert.Nil(t, err) {
+					assert.Equal(t, tc.expectedMountpoint, mountPoint)
+				}
+			}
+		})
+	}
+}

main.go

@@ -65,7 +65,7 @@ func main() {
 	log.SetFlags(log.Ldate | log.Ltime | log.Lmicroseconds)
 	if strings.ToLower(os.Getenv("ENABLE_GCSFUSE_VIPER_CONFIG")) == "true" {
 		// TODO: implement the mount logic instead of simply returning nil.
-		rootCmd, err := cmd.NewRootCmd(func(config cfg.Config) error { return nil })
+		rootCmd, err := cmd.NewRootCmd(func(*cfg.Config, string, string) error { return nil })
 		if err != nil {
 			log.Fatalf("Error occurred while creating the root command: %v", err)
 		}