dockerfile: maintain osversion/variant from the base image

Restores the behavior from v0.12.

Signed-off-by: Tonis Tiigi <[email protected]>

Author: tonistiigi

frontend/dockerfile/dockerfile2llb/convert.go

@@ -801,10 +801,15 @@ func toDispatchState(ctx context.Context, dt []byte, opt ConvertOpt) (*dispatchS
 	target.state = target.state.SetMarshalDefaults(defaults...)
 
 	if !platformOpt.implicitTarget {
+		sameOsArch := platformOpt.targetPlatform.OS == target.image.OS && platformOpt.targetPlatform.Architecture == target.image.Architecture
 		target.image.OS = platformOpt.targetPlatform.OS
 		target.image.Architecture = platformOpt.targetPlatform.Architecture
-		target.image.Variant = platformOpt.targetPlatform.Variant
-		target.image.OSVersion = platformOpt.targetPlatform.OSVersion
+		if platformOpt.targetPlatform.Variant != "" || !sameOsArch {
+			target.image.Variant = platformOpt.targetPlatform.Variant
+		}
+		if platformOpt.targetPlatform.OSVersion != "" || !sameOsArch {
+			target.image.OSVersion = platformOpt.targetPlatform.OSVersion
+		}
 		if platformOpt.targetPlatform.OSFeatures != nil {
 			target.image.OSFeatures = append([]string{}, platformOpt.targetPlatform.OSFeatures...)
 		}

frontend/dockerfile/dockerfile_test.go

@@ -217,6 +217,7 @@ var allTests = integration.TestFuncs(
 	testPowershellInDefaultPathOnWindows,
 	testOCILayoutMultiname,
 	testPlatformWithOSVersion,
+	testMaintainBaseOSVersion,
 )
 
 // Tests that depend on the `security.*` entitlements
@@ -9634,6 +9635,119 @@ EOF
 	require.Equal(t, p2.OSVersion+"\n", string(dt))
 }
 
+func testMaintainBaseOSVersion(t *testing.T, sb integration.Sandbox) {
+	integration.SkipOnPlatform(t, "windows")
+	workers.CheckFeatureCompat(t, sb, workers.FeatureDirectPush)
+
+	ctx := sb.Context()
+
+	c, err := client.New(ctx, sb.Address())
+	require.NoError(t, err)
+	defer c.Close()
+
+	f := getFrontend(t, sb)
+
+	p1 := ocispecs.Platform{
+		OS:           "windows",
+		OSVersion:    "10.20.30",
+		Architecture: "amd64",
+	}
+	p1Str := platforms.FormatAll(p1)
+
+	registry, err := sb.NewRegistry()
+	if errors.Is(err, integration.ErrRequirements) {
+		t.Skip(err.Error())
+	}
+	require.NoError(t, err)
+	target := registry + "/buildkit/testplatformwithosversion-1:latest"
+
+	dockerfile := []byte(`
+FROM scratch
+ARG TARGETPLATFORM
+COPY <<EOF /platform
+${TARGETPLATFORM}
+EOF
+`)
+
+	dir := integration.Tmpdir(
+		t,
+		fstest.CreateFile("Dockerfile", dockerfile, 0600),
+	)
+
+	_, err = f.Solve(sb.Context(), c, client.SolveOpt{
+		FrontendAttrs: map[string]string{
+			"platform": p1Str,
+		},
+		Exports: []client.ExportEntry{
+			{
+				Type: client.ExporterImage,
+				Attrs: map[string]string{
+					"name": target,
+					"push": "true",
+				},
+			},
+		},
+
+		LocalMounts: map[string]fsutil.FS{
+			dockerui.DefaultLocalNameDockerfile: dir,
+			dockerui.DefaultLocalNameContext:    dir,
+		},
+	}, nil)
+
+	require.NoError(t, err)
+
+	desc, provider, err := contentutil.ProviderFromRef(target)
+	require.NoError(t, err)
+
+	info, err := testutil.ReadImages(ctx, provider, desc)
+	require.NoError(t, err)
+	require.Len(t, info.Images, 1)
+	require.Equal(t, info.Images[0].Img.Platform.OSVersion, p1.OSVersion)
+
+	dockerfile = []byte(fmt.Sprintf(`
+FROM %s
+COPY <<EOF /other
+hello
+EOF
+`, target))
+
+	dir = integration.Tmpdir(
+		t,
+		fstest.CreateFile("Dockerfile", dockerfile, 0600),
+	)
+
+	target2 := registry + "/buildkit/testplatformwithosversion-2:latest"
+
+	_, err = f.Solve(sb.Context(), c, client.SolveOpt{
+		FrontendAttrs: map[string]string{
+			"platform": p1.OS + "/" + p1.Architecture,
+		},
+		Exports: []client.ExportEntry{
+			{
+				Type: client.ExporterImage,
+				Attrs: map[string]string{
+					"name": target2,
+					"push": "true",
+				},
+			},
+		},
+
+		LocalMounts: map[string]fsutil.FS{
+			dockerui.DefaultLocalNameDockerfile: dir,
+			dockerui.DefaultLocalNameContext:    dir,
+		},
+	}, nil)
+	require.NoError(t, err)
+
+	desc, provider, err = contentutil.ProviderFromRef(target2)
+	require.NoError(t, err)
+
+	info, err = testutil.ReadImages(ctx, provider, desc)
+	require.NoError(t, err)
+	require.Len(t, info.Images, 1)
+	require.Equal(t, info.Images[0].Img.Platform.OSVersion, p1.OSVersion)
+}
+
 func runShell(dir string, cmds ...string) error {
 	for _, args := range cmds {
 		var cmd *exec.Cmd