refactor(oci-layout): use Parser to process option input

cmd/oras/attach.go

@@ -65,7 +65,7 @@ Example - Attach file 'hi.txt' and export the pushed manifest to 'manifest.json'
 `,
 		Args: cobra.MinimumNArgs(1),
 		PreRunE: func(cmd *cobra.Command, args []string) error {
-			return opts.ReadPassword()
+			return option.Parse(&opts)
 		},
 		RunE: func(cmd *cobra.Command, args []string) error {
 			opts.targetRef = args[0]

cmd/oras/blob/delete.go

@@ -59,7 +59,7 @@ Example - Delete a blob and print its descriptor:
 			if opts.OutputDescriptor && !opts.Confirmed {
 				return errors.New("must apply --force to confirm the deletion if the descriptor is outputted")
 			}
-			return opts.ReadPassword()
+			return option.Parse(&opts)
 		},
 		RunE: func(cmd *cobra.Command, args []string) error {
 			opts.targetRef = args[0]

cmd/oras/blob/fetch.go

@@ -70,7 +70,7 @@ Example - Fetch the blob, save it to a local file and print the descriptor:
 				return errors.New("`--output -` cannot be used with `--descriptor` at the same time")
 			}
 
-			return opts.ReadPassword()
+			return option.Parse(&opts)
 		},
 		Aliases: []string{"get"},
 		RunE: func(cmd *cobra.Command, args []string) error {

cmd/oras/blob/push.go

@@ -81,7 +81,7 @@ Example - Push blob without TLS:
 					return errors.New("`--size` must be provided if the blob is read from stdin")
 				}
 			}
-			return opts.ReadPassword()
+			return option.Parse(&opts)
 		},
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return pushBlob(opts)

cmd/oras/cp.go

@@ -68,6 +68,9 @@ Example - Copy the artifact tagged with 'v1' from repository 'localhost:5000/net
   oras cp --concurrency 6 localhost:5000/net-monitor:v1 localhost:5000/net-monitor-copy:v1,tag2,tag3
 `,
 		Args: cobra.ExactArgs(2),
+		PreRunE: func(cmd *cobra.Command, args []string) error {
+			return option.Parse(&opts)
+		},
 		RunE: func(cmd *cobra.Command, args []string) error {
 			opts.srcRef = args[0]
 			refs := strings.Split(args[1], ",")
@@ -88,10 +91,6 @@ Example - Copy the artifact tagged with 'v1' from repository 'localhost:5000/net
 
 func runCopy(opts copyOptions) error {
 	ctx, _ := opts.SetLoggerLevel()
-	targetPlatform, err := opts.Parse()
-	if err != nil {
-		return err
-	}
 
 	// Prepare source
 	src, err := opts.src.NewRepository(opts.srcRef, opts.Common)
@@ -145,9 +144,7 @@ func runCopy(opts copyOptions) error {
 			copyOptions := oras.CopyOptions{
 				CopyGraphOptions: extendedCopyOptions.CopyGraphOptions,
 			}
-			if targetPlatform != nil {
-				copyOptions.WithTargetPlatform(targetPlatform)
-			}
+			copyOptions.WithTargetPlatform(opts.OCIPlatform)
 			desc, err = oras.Copy(ctx, src, opts.srcRef, dst, opts.dstRef, copyOptions)
 		}
 	}

cmd/oras/discover.go

@@ -63,7 +63,7 @@ Example - Discover referrers with type 'test-artifact' of manifest 'hello:latest
 `,
 		Args: cobra.ExactArgs(1),
 		PreRunE: func(cmd *cobra.Command, args []string) error {
-			return opts.ReadPassword()
+			return option.Parse(&opts)
 		},
 		RunE: func(cmd *cobra.Command, args []string) error {
 			opts.targetRef = args[0]
@@ -86,14 +86,10 @@ func runDiscover(opts discoverOptions) error {
 	if repo.Reference.Reference == "" {
 		return errors.NewErrInvalidReference(repo.Reference)
 	}
-	targetPlatform, err := opts.Parse()
-	if err != nil {
-		return err
-	}
 
 	// discover artifacts
 	resolveOpts := oras.DefaultResolveOptions
-	resolveOpts.TargetPlatform = targetPlatform
+	resolveOpts.TargetPlatform = opts.OCIPlatform
 	desc, err := oras.Resolve(ctx, repo, repo.Reference.Reference, resolveOpts)
 	if err != nil {
 		return err

cmd/oras/internal/option/parser.go

@@ -0,0 +1,41 @@
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package option
+
+import (
+	"reflect"
+)
+
+// FlagParser parses flags in an option.
+type FlagParser interface {
+	Parse() error
+}
+
+// Parse parses applicable fields of the passed-in option pointer and returns
+// error during parsing.
+func Parse(optsPtr interface{}) error {
+	v := reflect.ValueOf(optsPtr).Elem()
+	for i := 0; i < v.NumField(); i++ {
+		f := v.Field(i)
+		if f.CanSet() {
+			iface := f.Addr().Interface()
+			if a, ok := iface.(FlagParser); ok {
+				if err := a.Parse(); err != nil {
+					return err
+				}
+			}
+		}
+	}
+	return nil
+}

cmd/oras/internal/option/parser_test.go

@@ -0,0 +1,53 @@
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package option_test
+
+import (
+	"testing"
+
+	"oras.land/oras/cmd/oras/internal/option"
+)
+
+type Test struct {
+	Cnt int
+}
+
+func (t *Test) Parse() error {
+	t.Cnt += 1
+	return nil
+}
+
+func TestParse(t *testing.T) {
+	type args struct {
+		Test
+	}
+	tests := []struct {
+		name    string
+		args    args
+		wantErr bool
+	}{
+		{"parse should be called", args{Test{Cnt: 0}}, false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if err := option.Parse(&tt.args); (err != nil) != tt.wantErr {
+				t.Errorf("Parse() error = %v, wantErr %v", err, tt.wantErr)
+			}
+
+			if tt.args.Cnt != 1 {
+				t.Errorf("Expect Parse() to be called once but got %v", tt.args.Cnt)
+			}
+		})
+	}
+}

cmd/oras/internal/option/platform.go

@@ -3,9 +3,7 @@ Copyright The ORAS Authors.
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
-
 http://www.apache.org/licenses/LICENSE-2.0
-
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -26,25 +24,26 @@ import (
 
 // Platform option struct.
 type Platform struct {
-	Platform string
+	platform    string
+	OCIPlatform *ocispec.Platform
 }
 
 // ApplyFlags applies flags to a command flag set.
 func (opts *Platform) ApplyFlags(fs *pflag.FlagSet) {
-	fs.StringVarP(&opts.Platform, "platform", "", "", "request platform in the form of `os[/arch][/variant][:os_version]`")
+	fs.StringVarP(&opts.platform, "platform", "", "", "request platform in the form of `os[/arch][/variant][:os_version]`")
 }
 
 // parse parses the input platform flag to an oci platform type.
-func (opts *Platform) Parse() (*ocispec.Platform, error) {
-	if opts.Platform == "" {
-		return nil, nil
+func (opts *Platform) Parse() error {
+	if opts.platform == "" {
+		return nil
 	}
 
 	// OS[/Arch[/Variant]][:OSVersion]
 	// If Arch is not provided, will use GOARCH instead
 	var platformStr string
 	var p ocispec.Platform
-	platformStr, p.OSVersion, _ = strings.Cut(opts.Platform, ":")
+	platformStr, p.OSVersion, _ = strings.Cut(opts.platform, ":")
 	parts := strings.Split(platformStr, "/")
 	switch len(parts) {
 	case 3:
@@ -55,14 +54,15 @@ func (opts *Platform) Parse() (*ocispec.Platform, error) {
 	case 1:
 		p.Architecture = runtime.GOARCH
 	default:
-		return nil, fmt.Errorf("failed to parse platform %q: expected format os[/arch[/variant]]", opts.Platform)
+		return fmt.Errorf("failed to parse platform %q: expected format os[/arch[/variant]]", opts.platform)
 	}
 	p.OS = parts[0]
 	if p.OS == "" {
-		return nil, fmt.Errorf("invalid platform: OS cannot be empty")
+		return fmt.Errorf("invalid platform: OS cannot be empty")
 	}
 	if p.Architecture == "" {
-		return nil, fmt.Errorf("invalid platform: Architecture cannot be empty")
+		return fmt.Errorf("invalid platform: Architecture cannot be empty")
 	}
-	return &p, nil
+	opts.OCIPlatform = &p
+	return nil
 }

cmd/oras/internal/option/platform_test.go

@@ -3,9 +3,7 @@ Copyright The ORAS Authors.
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
-
 http://www.apache.org/licenses/LICENSE-2.0
-
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -27,8 +25,8 @@ import (
 func TestPlatform_ApplyFlags(t *testing.T) {
 	var test struct{ Platform }
 	ApplyFlags(&test, pflag.NewFlagSet("oras-test", pflag.ExitOnError))
-	if test.Platform.Platform != "" {
-		t.Fatalf("expecting platform to be empty but got: %v", test.Platform.Platform)
+	if test.Platform.platform != "" {
+		t.Fatalf("expecting platform to be empty but got: %v", test.Platform.platform)
 	}
 }
 
@@ -37,15 +35,15 @@ func TestPlatform_Parse_err(t *testing.T) {
 		name string
 		opts *Platform
 	}{
-		{name: "empty arch 1", opts: &Platform{"os/"}},
-		{name: "empty arch 2", opts: &Platform{"os//variant"}},
-		{name: "empty os", opts: &Platform{"/arch"}},
-		{name: "empty os with variant", opts: &Platform{"/arch/variant"}},
-		{name: "trailing slash", opts: &Platform{"os/arch/variant/llama"}},
+		{name: "empty arch 1", opts: &Platform{"os/", nil}},
+		{name: "empty arch 2", opts: &Platform{"os//variant", nil}},
+		{name: "empty os", opts: &Platform{"/arch", nil}},
+		{name: "empty os with variant", opts: &Platform{"/arch/variant", nil}},
+		{name: "trailing slash", opts: &Platform{"os/arch/variant/llama", nil}},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			_, err := tt.opts.Parse()
+			err := tt.opts.Parse()
 			if err == nil {
 				t.Errorf("Platform.Parse() error = %v, wantErr %v", err, true)
 				return
@@ -60,21 +58,20 @@ func TestPlatform_Parse(t *testing.T) {
 		opts *Platform
 		want *ocispec.Platform
 	}{
-		{name: "empty", opts: &Platform{""}, want: nil},
-		{name: "default arch", opts: &Platform{"os"}, want: &ocispec.Platform{OS: "os", Architecture: runtime.GOARCH}},
-		{name: "os&arch", opts: &Platform{"os/aRcH"}, want: &ocispec.Platform{OS: "os", Architecture: "aRcH"}},
-		{name: "empty variant", opts: &Platform{"os/aRcH/"}, want: &ocispec.Platform{OS: "os", Architecture: "aRcH", Variant: ""}},
-		{name: "os&arch&variant", opts: &Platform{"os/aRcH/vAriAnt"}, want: &ocispec.Platform{OS: "os", Architecture: "aRcH", Variant: "vAriAnt"}},
-		{name: "os version", opts: &Platform{"os/aRcH/vAriAnt:osversion"}, want: &ocispec.Platform{OS: "os", Architecture: "aRcH", Variant: "vAriAnt", OSVersion: "osversion"}},
-		{name: "long os version", opts: &Platform{"os/aRcH"}, want: &ocispec.Platform{OS: "os", Architecture: "aRcH"}},
+		{name: "empty", opts: &Platform{platform: ""}, want: nil},
+		{name: "default arch", opts: &Platform{platform: "os"}, want: &ocispec.Platform{OS: "os", Architecture: runtime.GOARCH}},
+		{name: "os&arch", opts: &Platform{platform: "os/aRcH"}, want: &ocispec.Platform{OS: "os", Architecture: "aRcH"}},
+		{name: "empty variant", opts: &Platform{platform: "os/aRcH/"}, want: &ocispec.Platform{OS: "os", Architecture: "aRcH", Variant: ""}},
+		{name: "os&arch&variant", opts: &Platform{platform: "os/aRcH/vAriAnt"}, want: &ocispec.Platform{OS: "os", Architecture: "aRcH", Variant: "vAriAnt"}},
+		{name: "os version", opts: &Platform{platform: "os/aRcH/vAriAnt:osversion"}, want: &ocispec.Platform{OS: "os", Architecture: "aRcH", Variant: "vAriAnt", OSVersion: "osversion"}},
+		{name: "long os version", opts: &Platform{platform: "os/aRcH"}, want: &ocispec.Platform{OS: "os", Architecture: "aRcH"}},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			got, err := tt.opts.Parse()
-			if err != nil {
+			if err := tt.opts.Parse(); err != nil {
 				t.Errorf("Platform.Parse() error = %v", err)
-				return
 			}
+			got := tt.opts.OCIPlatform
 			if !reflect.DeepEqual(got, tt.want) {
 				t.Errorf("Platform.Parse() = %v, want %v", got, tt.want)
 			}

cmd/oras/internal/option/remote.go

@@ -87,8 +87,8 @@ func (opts *Remote) ApplyFlagsWithPrefix(fs *pflag.FlagSet, prefix, description
 	}
 }
 
-// ReadPassword tries to read password with optional cmd prompt.
-func (opts *Remote) ReadPassword() (err error) {
+// Parse tries to read password with optional cmd prompt.
+func (opts *Remote) Parse() error {
 	if opts.Password != "" {
 		fmt.Fprintln(os.Stderr, "WARNING! Using --password via the CLI is insecure. Use --password-stdin.")
 	} else if opts.PasswordFromStdin {

cmd/oras/login.go

@@ -61,7 +61,7 @@ Example - Log in with username and password in an interactive terminal and no TL
 `,
 		Args: cobra.ExactArgs(1),
 		PreRunE: func(cmd *cobra.Command, args []string) error {
-			return opts.ReadPassword()
+			return option.Parse(&opts)
 		},
 		RunE: func(cmd *cobra.Command, args []string) error {
 			opts.Hostname = args[0]
@@ -130,9 +130,9 @@ func runLogin(opts loginOptions) (err error) {
 	return nil
 }
 
-func readLine(prompt string, slient bool) (string, error) {
+func readLine(prompt string, silent bool) (string, error) {
 	fmt.Print(prompt)
-	if slient {
+	if silent {
 		fd := os.Stdin.Fd()
 		state, err := term.SaveState(fd)
 		if err != nil {
@@ -147,7 +147,7 @@ func readLine(prompt string, slient bool) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	if slient {
+	if silent {
 		fmt.Println()
 	}
 

cmd/oras/manifest/delete.go

@@ -63,7 +63,7 @@ Example - Delete a manifest by digest 'sha256:99e4703fbf30916f549cd6bfa9cdbab614
 			if opts.OutputDescriptor && !opts.Confirmed {
 				return errors.New("must apply --force to confirm the deletion if the descriptor is outputted")
 			}
-			return opts.ReadPassword()
+			return option.Parse(&opts)
 		},
 		RunE: func(_ *cobra.Command, args []string) error {
 			opts.targetRef = args[0]