From 90c884a2b53965bcf577ed1c2151705f859cb52e Mon Sep 17 00:00:00 2001
From: Dean Chen <862469039@qq.com>
Date: Thu, 29 Oct 2026 21:45:30 +0500
Subject: [PATCH] manifest: allow an empty --variant to clear it

annotate only wrote the variant when the string was non-empty, so
`--variant ""` left the previous value in place.

Fixes #4352

Signed-off-by: Dean Chen <862469039@qq.com>
---
 cli/command/manifest/annotate.go      |  8 ++++---
 cli/command/manifest/annotate_test.go | 32 +++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/cli/command/manifest/annotate.go b/cli/command/manifest/annotate.go
index a9507deb73f0..7231d161e1de 100644
--- a/cli/command/manifest/annotate.go
+++ b/cli/command/manifest/annotate.go
@@ -84,7 +84,7 @@ func newAnnotateCommand(dockerCLI command.Cli) *cobra.Command {
 		RunE: func(cmd *cobra.Command, args []string) error {
 			opts.target = args[0]
 			opts.image = args[1]
-			return runManifestAnnotate(dockerCLI, opts)
+			return runManifestAnnotate(dockerCLI, cmd, opts)
 		},
 		DisableFlagsInUseLine: true,
 	}
@@ -100,7 +100,7 @@ func newAnnotateCommand(dockerCLI command.Cli) *cobra.Command {
 	return cmd
 }
 
-func runManifestAnnotate(dockerCLI command.Cli, opts annotateOptions) error {
+func runManifestAnnotate(dockerCLI command.Cli, cmd *cobra.Command, opts annotateOptions) error {
 	targetRef, err := normalizeReference(opts.target)
 	if err != nil {
 		return fmt.Errorf("annotate: error parsing name for manifest list %s: %w", opts.target, err)
@@ -132,7 +132,9 @@ func runManifestAnnotate(dockerCLI command.Cli, opts annotateOptions) error {
 	for _, osFeature := range opts.osFeatures {
 		imageManifest.Descriptor.Platform.OSFeatures = appendIfUnique(imageManifest.Descriptor.Platform.OSFeatures, osFeature)
 	}
-	if opts.variant != "" {
+	// An empty --variant is how you clear one. The zero value is also the
+	// default when the flag is omitted, so only write it when it was set.
+	if cmd.Flags().Changed("variant") {
 		imageManifest.Descriptor.Platform.Variant = opts.variant
 	}
 	if opts.osVersion != "" {
diff --git a/cli/command/manifest/annotate_test.go b/cli/command/manifest/annotate_test.go
index f2c924e45ffc..5a7527e2259e 100644
--- a/cli/command/manifest/annotate_test.go
+++ b/cli/command/manifest/annotate_test.go
@@ -11,6 +11,38 @@ import (
 	"gotest.tools/v3/golden"
 )
 
+func TestManifestAnnotateClearsVariant(t *testing.T) {
+	manifestStore := store.NewStore(t.TempDir())
+
+	cli := test.NewFakeCli(nil)
+	cli.SetManifestStore(manifestStore)
+	namedRef := ref(t, "alpine:3.0")
+	imageManifest := fullImageManifest(t, namedRef)
+	imageManifest.Descriptor.Platform.Variant = "v7"
+	err := manifestStore.Save(ref(t, "list:v1"), namedRef, imageManifest)
+	assert.NilError(t, err)
+
+	cmd := newAnnotateCommand(cli)
+	cmd.SetArgs([]string{"--os", "linux", "example.com/list:v1", "example.com/alpine:3.0"})
+	cmd.SetOut(io.Discard)
+	cmd.SetErr(io.Discard)
+	assert.NilError(t, cmd.Execute())
+
+	got, err := manifestStore.Get(ref(t, "list:v1"), namedRef)
+	assert.NilError(t, err)
+	assert.Check(t, is.Equal("v7", got.Descriptor.Platform.Variant))
+
+	cmd = newAnnotateCommand(cli)
+	cmd.SetArgs([]string{"--variant", "", "example.com/list:v1", "example.com/alpine:3.0"})
+	cmd.SetOut(io.Discard)
+	cmd.SetErr(io.Discard)
+	assert.NilError(t, cmd.Execute())
+
+	got, err = manifestStore.Get(ref(t, "list:v1"), namedRef)
+	assert.NilError(t, err)
+	assert.Check(t, is.Equal("", got.Descriptor.Platform.Variant))
+}
+
 func TestManifestAnnotateError(t *testing.T) {
 	testCases := []struct {
 		args          []string