exporter/containerimage: normalize platform in annotation keys

exporter/containerimage/annotations.go

@@ -71,7 +71,7 @@ func (ag AnnotationsGroup) Platform(p *ocispecs.Platform) *Annotations {
 
 	ps := []string{""}
 	if p != nil {
-		ps = append(ps, platforms.FormatAll(*p))
+		ps = append(ps, platforms.FormatAll(platforms.Normalize(*p)))
 	}
 
 	for _, a := range ag {

exporter/containerimage/annotations_test.go

@@ -0,0 +1,33 @@
+package containerimage
+
+import (
+	"testing"
+
+	"github.com/moby/buildkit/exporter/containerimage/exptypes"
+	ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAnnotationsPlatformNormalized(t *testing.T) {
+	ag, rest, err := ParseAnnotations(map[string][]byte{
+		"annotation-manifest-descriptor[linux/arm64/v8].example": []byte("v"),
+	})
+	require.NoError(t, err)
+	require.Empty(t, rest)
+
+	for _, p := range []ocispecs.Platform{
+		{OS: "linux", Architecture: "arm64"},
+		{OS: "linux", Architecture: "arm64", Variant: "v8"},
+	} {
+		a := ag.Platform(&p)
+		require.Equal(t, map[string]string{"example": "v"}, a.ManifestDescriptor, p)
+	}
+
+	a := ag.Platform(&ocispecs.Platform{OS: "linux", Architecture: "amd64"})
+	require.Empty(t, a.ManifestDescriptor)
+
+	k, ok, err := exptypes.ParseAnnotationKey("annotation-manifest[linux/arm64/v8].k")
+	require.NoError(t, err)
+	require.True(t, ok)
+	require.Equal(t, "linux/arm64", k.PlatformString())
+}

exporter/containerimage/exptypes/annotations.go

@@ -103,6 +103,7 @@ func ParseAnnotationKey(result string) (AnnotationKey, bool, error) {
 		if err != nil {
 			return AnnotationKey{}, true, err
 		}
+		p = platforms.Normalize(p)
 		ociPlatform = &p
 	}