feat: Use cobra.Command.OutOrStdout method for output

cmd/oras/root/blob/delete.go

@@ -82,13 +82,14 @@ func deleteBlob(cmd *cobra.Command, opts *deleteBlobOptions) (err error) {
 	}
 
 	// add both pull and delete scope hints for dst repository to save potential delete-scope token requests during deleting
+	outWriter := cmd.OutOrStdout()
 	ctx = registryutil.WithScopeHint(ctx, blobs, auth.ActionPull, auth.ActionDelete)
 	desc, err := blobs.Resolve(ctx, opts.Reference)
 	if err != nil {
 		if errors.Is(err, errdef.ErrNotFound) {
 			if opts.Force && !opts.OutputDescriptor {
 				// ignore nonexistent
-				fmt.Println("Missing", opts.RawReference)
+				fmt.Fprintln(outWriter, "Missing", opts.RawReference)
 				return nil
 			}
 			return fmt.Errorf("%s: the specified blob does not exist", opts.RawReference)
@@ -117,7 +118,7 @@ func deleteBlob(cmd *cobra.Command, opts *deleteBlobOptions) (err error) {
 		return opts.Output(os.Stdout, descJSON)
 	}
 
-	fmt.Println("Deleted", opts.AnnotatedReference())
+	fmt.Fprintln(outWriter, "Deleted", opts.AnnotatedReference())
 
 	return nil
 }

cmd/oras/root/blob/push.go

@@ -137,8 +137,9 @@ func pushBlob(cmd *cobra.Command, opts *pushBlobOptions) (err error) {
 		return opts.Output(os.Stdout, descJSON)
 	}
 
-	fmt.Println("Pushed", opts.AnnotatedReference())
-	fmt.Println("Digest:", desc.Digest)
+	outWriter := cmd.OutOrStdout()
+	fmt.Fprintln(outWriter, "Pushed", opts.AnnotatedReference())
+	fmt.Fprintln(outWriter, "Digest:", desc.Digest)
 
 	return nil
 }

cmd/oras/root/cp.go

@@ -134,7 +134,8 @@ func runCopy(cmd *cobra.Command, opts *copyOptions) error {
 		// correct source digest
 		opts.From.RawReference = fmt.Sprintf("%s@%s", opts.From.Path, desc.Digest.String())
 	}
-	fmt.Println("Copied", opts.From.AnnotatedReference(), "=>", opts.To.AnnotatedReference())
+	outWriter := cmd.OutOrStdout()
+	fmt.Fprintln(outWriter, "Copied", opts.From.AnnotatedReference(), "=>", opts.To.AnnotatedReference())
 
 	if len(opts.extraRefs) != 0 {
 		tagNOpts := oras.DefaultTagNOptions
@@ -144,7 +145,7 @@ func runCopy(cmd *cobra.Command, opts *copyOptions) error {
 		}
 	}
 
-	fmt.Println("Digest:", desc.Digest)
+	fmt.Fprintln(outWriter, "Digest:", desc.Digest)
 
 	return nil
 }

cmd/oras/root/discover.go

@@ -19,6 +19,7 @@
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"os"
 	"strings"
 
@@ -127,15 +128,16 @@
 		return printDiscoveredReferrersJSON(desc, refs)
 	}
 
+	outWriter := cmd.OutOrStdout()
 	if n := len(refs); n > 1 {
-		fmt.Println("Discovered", n, "artifacts referencing", opts.Reference)
+		fmt.Fprintln(outWriter, "Discovered", n, "artifacts referencing", opts.Reference)
 	} else {
-		fmt.Println("Discovered", n, "artifact referencing", opts.Reference)
+		fmt.Fprintln(outWriter, "Discovered", n, "artifact referencing", opts.Reference)
 	}
-	fmt.Println("Digest:", desc.Digest)
+	fmt.Fprintln(outWriter, "Digest:", desc.Digest)
 	if len(refs) > 0 {
-		fmt.Println()
-		_ = printDiscoveredReferrersTable(refs, opts.Verbose)
+		fmt.Fprintln(outWriter)
+		_ = printDiscoveredReferrersTable(outWriter, refs, opts.Verbose)
 	}
 	return nil
 }
@@ -173,7 +175,7 @@
 	return nil
 }
 
-func printDiscoveredReferrersTable(refs []ocispec.Descriptor, verbose bool) error {
+func printDiscoveredReferrersTable(outWriter io.Writer, refs []ocispec.Descriptor, verbose bool) error {
 	typeNameTitle := "Artifact Type"
 	typeNameLength := len(typeNameTitle)
 	for _, ref := range refs {
@@ -183,7 +185,7 @@
 	}
 
 	print := func(key string, value interface{}) {
-		fmt.Println(key, strings.Repeat(" ", typeNameLength-len(key)+1), value)
+		fmt.Fprintln(outWriter, key, strings.Repeat(" ", typeNameLength-len(key)+1), value)
 	}
 
 	print(typeNameTitle, "Digest")

cmd/oras/root/login.go

@@ -18,6 +18,7 @@
 import (
 	"errors"
 	"fmt"
+	"io"
 	"os"
 	"strings"
 
@@ -28,7 +29,7 @@
 	oerrors "oras.land/oras/cmd/oras/internal/errors"
 	"oras.land/oras/cmd/oras/internal/option"
 	"oras.land/oras/internal/credential"
-	"oras.land/oras/internal/io"
+	orasio "oras.land/oras/internal/io"
 )
 
 type loginOptions struct {
@@ -77,27 +78,28 @@
 
 func runLogin(cmd *cobra.Command, opts loginOptions) (err error) {
 	ctx, logger := opts.WithContext(cmd.Context())
+	outWriter := cmd.OutOrStdout()
 
 	// prompt for credential
 	if opts.Password == "" {
 		if opts.Username == "" {
 			// prompt for username
-			username, err := readLine("Username: ", false)
+			username, err := readLine(outWriter, "Username: ", false)
 			if err != nil {
 				return err
 			}
 			opts.Username = strings.TrimSpace(username)
 		}
 		if opts.Username == "" {
 			// prompt for token
-			if opts.Password, err = readLine("Token: ", true); err != nil {
+			if opts.Password, err = readLine(outWriter, "Token: ", true); err != nil {
 				return err
 			} else if opts.Password == "" {
 				return errors.New("token required")
 			}
 		} else {
 			// prompt for password
-			if opts.Password, err = readLine("Password: ", true); err != nil {
+			if opts.Password, err = readLine(outWriter, "Password: ", true); err != nil {
 				return err
 			} else if opts.Password == "" {
 				return errors.New("password required")
@@ -116,21 +118,21 @@
 	if err = credentials.Login(ctx, store, remote, opts.Credential()); err != nil {
 		return err
 	}
-	fmt.Println("Login Succeeded")
+	fmt.Fprintln(outWriter, "Login Succeeded")
 	return nil
 }
 
-func readLine(prompt string, silent bool) (string, error) {
-	fmt.Print(prompt)
+func readLine(outWriter io.Writer, prompt string, silent bool) (string, error) {
+	fmt.Fprint(outWriter, prompt)
 	fd := int(os.Stdin.Fd())
 	var bytes []byte
 	var err error
 	if silent && term.IsTerminal(fd) {
 		if bytes, err = term.ReadPassword(fd); err == nil {
-			_, err = fmt.Println()
+			_, err = fmt.Fprintln(outWriter)
 		}
 	} else {
-		bytes, err = io.ReadLine(os.Stdin)
+		bytes, err = orasio.ReadLine(os.Stdin)
 	}
 	if err != nil {
 		return "", err

cmd/oras/root/manifest/delete.go

@@ -91,13 +91,14 @@ func deleteManifest(cmd *cobra.Command, opts *deleteOptions) error {
 		// possibly needed when adding a new referrers index
 		hints = append(hints, auth.ActionPush)
 	}
+	outWriter := cmd.OutOrStdout()
 	ctx = registryutil.WithScopeHint(ctx, manifests, hints...)
 	desc, err := manifests.Resolve(ctx, opts.Reference)
 	if err != nil {
 		if errors.Is(err, errdef.ErrNotFound) {
 			if opts.Force && !opts.OutputDescriptor {
 				// ignore nonexistent
-				fmt.Println("Missing", opts.RawReference)
+				fmt.Fprintln(outWriter, "Missing", opts.RawReference)
 				return nil
 			}
 			return fmt.Errorf("%s: the specified manifest does not exist", opts.RawReference)
@@ -126,7 +127,7 @@ func deleteManifest(cmd *cobra.Command, opts *deleteOptions) error {
 		return opts.Output(os.Stdout, descJSON)
 	}
 
-	fmt.Println("Deleted", opts.AnnotatedReference())
+	fmt.Fprintln(outWriter, "Deleted", opts.AnnotatedReference())
 
 	return nil
 }

cmd/oras/root/manifest/push.go

@@ -191,7 +191,7 @@ func pushManifest(cmd *cobra.Command, opts pushOptions) error {
 		}
 	}
 
-	fmt.Println("Digest:", desc.Digest)
+	fmt.Fprintln(cmd.OutOrStdout(), "Digest:", desc.Digest)
 
 	return nil
 }

cmd/oras/root/pull.go

@@ -143,12 +143,13 @@ func runPull(cmd *cobra.Command, opts *pullOptions) error {
 	}
 
 	// suggest oras copy for pulling layers without annotation
+	outWriter := cmd.OutOrStdout()
 	if layerSkipped {
-		fmt.Printf("Skipped pulling layers without file name in %q\n", ocispec.AnnotationTitle)
-		fmt.Printf("Use 'oras copy %s --to-oci-layout <layout-dir>' to pull all layers.\n", opts.RawReference)
+		fmt.Fprintf(outWriter, "Skipped pulling layers without file name in %q\n", ocispec.AnnotationTitle)
+		fmt.Fprintf(outWriter, "Use 'oras copy %s --to-oci-layout <layout-dir>' to pull all layers.\n", opts.RawReference)
 	} else {
-		fmt.Println("Pulled", opts.AnnotatedReference())
-		fmt.Println("Digest:", desc.Digest)
+		fmt.Fprintln(outWriter, "Pulled", opts.AnnotatedReference())
+		fmt.Fprintln(outWriter, "Digest:", desc.Digest)
 	}
 	return nil
 }

cmd/oras/root/repo/ls.go

@@ -77,9 +77,10 @@ func listRepository(cmd *cobra.Command, opts *repositoryOptions) error {
 		return err
 	}
 	err = reg.Repositories(ctx, opts.last, func(repos []string) error {
+		outWriter := cmd.OutOrStdout()
 		for _, repo := range repos {
 			if subRepo, found := strings.CutPrefix(repo, opts.namespace); found {
-				fmt.Println(subRepo)
+				fmt.Fprintln(outWriter, subRepo)
 			}
 		}
 		return nil

cmd/oras/root/repo/tags.go

@@ -98,14 +98,15 @@ func showTags(cmd *cobra.Command, opts *showTagsOptions) error {
 		}
 		logger.Warnf("[Experimental] querying tags associated to %s, it may take a while...\n", filter)
 	}
+	outWriter := cmd.OutOrStdout()
 	return finder.Tags(ctx, opts.last, func(tags []string) error {
 		for _, tag := range tags {
 			if opts.excludeDigestTag && isDigestTag(tag) {
 				continue
 			}
 			if filter != "" {
 				if tag == opts.Reference {
-					fmt.Println(tag)
+					fmt.Fprintln(outWriter, tag)
 					continue
 				}
 				desc, err := finder.Resolve(ctx, tag)
@@ -116,7 +117,7 @@ func showTags(cmd *cobra.Command, opts *showTagsOptions) error {
 					continue
 				}
 			}
-			fmt.Println(tag)
+			fmt.Fprintln(outWriter, tag)
 		}
 		return nil
 	})

cmd/oras/root/resolve.go

@@ -77,10 +77,11 @@ func runResolve(cmd *cobra.Command, opts *resolveOptions) error {
 		return fmt.Errorf("failed to resolve digest: %w", err)
 	}
 
+	outWriter := cmd.OutOrStdout()
 	if opts.fullRef {
-		fmt.Printf("%s@%s\n", opts.Path, desc.Digest)
+		fmt.Fprintf(outWriter, "%s@%s\n", opts.Path, desc.Digest)
 	} else {
-		fmt.Println(desc.Digest.String())
+		fmt.Fprintln(outWriter, desc.Digest.String())
 	}
 
 	return nil

cmd/oras/root/version.go

@@ -17,6 +17,7 @@ package root
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"runtime"
 	"strings"
@@ -45,14 +46,15 @@ Example - print version:
 			return nil
 		},
 		RunE: func(cmd *cobra.Command, args []string) error {
-			return runVersion()
+			outWriter := cmd.OutOrStdout()
+			return runVersion(outWriter)
 		},
 	}
 
 	return cmd
 }
 
-func runVersion() error {
+func runVersion(outWriter io.Writer) error {
 	items := [][]string{
 		{"Version", version.GetVersion()},
 		{"Go version", runtime.Version()},
@@ -71,7 +73,7 @@ func runVersion() error {
 		}
 	}
 	for _, item := range items {
-		fmt.Println(item[0] + ": " + strings.Repeat(" ", size-len(item[0])) + item[1])
+		fmt.Fprintln(outWriter, item[0]+": "+strings.Repeat(" ", size-len(item[0]))+item[1])
 	}
 
 	return nil