api: Change Platform field back to string (temporary workaround)

This partially reverts https://github.com/moby/moby/pull/37350

Although specs.Platform is desirable in the API, there is more work
to be done on helper functions, namely containerd's platforms.Parse
that assumes the default platform of the Go runtime.

That prevents a client to use the recommended Parse function to
retrieve a specs.Platform object.

With this change, no parsing is expected from the client.

Signed-off-by: Tibor Vass <tibor@docker.com>

api/server/router/build/build_routes.go

@@ -14,7 +14,6 @@ import (
 	"strings"
 	"sync"
 
-	"github.com/containerd/containerd/platforms"
 	"github.com/docker/docker/api/server/httputils"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/backend"
@@ -24,8 +23,7 @@ import (
 	"github.com/docker/docker/pkg/ioutils"
 	"github.com/docker/docker/pkg/progress"
 	"github.com/docker/docker/pkg/streamformatter"
-	"github.com/docker/docker/pkg/system"
-	"github.com/docker/go-units"
+	units "github.com/docker/go-units"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 )
@@ -72,17 +70,7 @@ func newImageBuildOptions(ctx context.Context, r *http.Request) (*types.ImageBui
 	options.Target = r.FormValue("target")
 	options.RemoteContext = r.FormValue("remote")
 	if versions.GreaterThanOrEqualTo(version, "1.32") {
-		apiPlatform := r.FormValue("platform")
-		if apiPlatform != "" {
-			sp, err := platforms.Parse(apiPlatform)
-			if err != nil {
-				return nil, err
-			}
-			if err := system.ValidatePlatform(sp); err != nil {
-				return nil, err
-			}
-			options.Platform = &sp
-		}
+		options.Platform = r.FormValue("platform")
 	}
 
 	if r.Form.Get("shmsize") != "" {

api/types/client.go

@@ -7,8 +7,7 @@ import (
 
 	"github.com/docker/docker/api/types/container"
 	"github.com/docker/docker/api/types/filters"
-	"github.com/docker/go-units"
-	specs "github.com/opencontainers/image-spec/specs-go/v1"
+	units "github.com/docker/go-units"
 )
 
 // CheckpointCreateOptions holds parameters to create a checkpoint from a container
@@ -181,7 +180,7 @@ type ImageBuildOptions struct {
 	ExtraHosts  []string // List of extra hosts
 	Target      string
 	SessionID   string
-	Platform    *specs.Platform
+	Platform    string
 	// Version specifies the version of the unerlying builder to use
 	Version BuilderVersion
 	// BuildID is an optional identifier that can be passed together with the

builder/builder-next/builder.go

@@ -14,6 +14,7 @@ import (
 	"github.com/docker/docker/builder"
 	"github.com/docker/docker/daemon/images"
 	"github.com/docker/docker/pkg/streamformatter"
+	"github.com/docker/docker/pkg/system"
 	controlapi "github.com/moby/buildkit/api/services/control"
 	"github.com/moby/buildkit/control"
 	"github.com/moby/buildkit/identity"
@@ -208,8 +209,17 @@ func (b *Builder) Build(ctx context.Context, opt backend.BuildConfig) (*builder.
 		frontendAttrs["no-cache"] = ""
 	}
 
-	if opt.Options.Platform != nil {
-		frontendAttrs["platform"] = platforms.Format(*opt.Options.Platform)
+	if opt.Options.Platform != "" {
+		// same as in newBuilder in builder/dockerfile.builder.go
+		// TODO: remove once opt.Options.Platform is of type specs.Platform
+		sp, err := platforms.Parse(opt.Options.Platform)
+		if err != nil {
+			return nil, err
+		}
+		if err := system.ValidatePlatform(sp); err != nil {
+			return nil, err
+		}
+		frontendAttrs["platform"] = opt.Options.Platform
 	}
 
 	exporterAttrs := map[string]string{}

builder/dockerfile/builder.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/containerd/containerd/platforms"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/backend"
 	"github.com/docker/docker/api/types/container"
@@ -25,6 +26,7 @@ import (
 	"github.com/moby/buildkit/frontend/dockerfile/parser"
 	"github.com/moby/buildkit/frontend/dockerfile/shell"
 	"github.com/moby/buildkit/session"
+	specs "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 	"golang.org/x/sync/syncmap"
@@ -111,7 +113,11 @@ func (bm *BuildManager) Build(ctx context.Context, config backend.BuildConfig) (
 		PathCache:      bm.pathCache,
 		IDMappings:     bm.idMappings,
 	}
-	return newBuilder(ctx, builderOptions).build(source, dockerfile)
+	b, err := newBuilder(ctx, builderOptions)
+	if err != nil {
+		return nil, err
+	}
+	return b.build(source, dockerfile)
 }
 
 func (bm *BuildManager) initializeClientSession(ctx context.Context, cancel func(), options *types.ImageBuildOptions) (builder.Source, error) {
@@ -175,10 +181,11 @@ type Builder struct {
 	pathCache        pathCache
 	containerManager *containerManager
 	imageProber      ImageProber
+	platform         *specs.Platform
 }
 
 // newBuilder creates a new Dockerfile builder from an optional dockerfile and a Options.
-func newBuilder(clientCtx context.Context, options builderOptions) *Builder {
+func newBuilder(clientCtx context.Context, options builderOptions) (*Builder, error) {
 	config := options.Options
 	if config == nil {
 		config = new(types.ImageBuildOptions)
@@ -199,7 +206,20 @@ func newBuilder(clientCtx context.Context, options builderOptions) *Builder {
 		containerManager: newContainerManager(options.Backend),
 	}
 
-	return b
+	// same as in Builder.Build in builder/builder-next/builder.go
+	// TODO: remove once config.Platform is of type specs.Platform
+	if config.Platform != "" {
+		sp, err := platforms.Parse(config.Platform)
+		if err != nil {
+			return nil, err
+		}
+		if err := system.ValidatePlatform(sp); err != nil {
+			return nil, err
+		}
+		b.platform = &sp
+	}
+
+	return b, nil
 }
 
 // Build 'LABEL' command(s) from '--label' options and add to the last stage
@@ -365,9 +385,12 @@ func BuildFromConfig(config *container.Config, changes []string, os string) (*co
 		return nil, errdefs.InvalidParameter(err)
 	}
 
-	b := newBuilder(context.Background(), builderOptions{
+	b, err := newBuilder(context.Background(), builderOptions{
 		Options: &types.ImageBuildOptions{NoCache: true},
 	})
+	if err != nil {
+		return nil, err
+	}
 
 	// ensure that the commands are valid
 	for _, n := range dockerfile.AST.Children {

builder/dockerfile/copy.go

@@ -87,7 +87,7 @@ func copierFromDispatchRequest(req dispatchRequest, download sourceDownloader, i
 		pathCache:   req.builder.pathCache,
 		download:    download,
 		imageSource: imageSource,
-		platform:    req.builder.options.Platform,
+		platform:    req.builder.platform,
 	}
 }
 

builder/dockerfile/dispatchers.go

@@ -146,7 +146,7 @@ func (d *dispatchRequest) getImageMount(imageRefOrID string) (*imageMount, error
 		imageRefOrID = stage.Image
 		localOnly = true
 	}
-	return d.builder.imageSources.Get(imageRefOrID, localOnly, d.builder.options.Platform)
+	return d.builder.imageSources.Get(imageRefOrID, localOnly, d.builder.platform)
 }
 
 // FROM [--platform=platform] imagename[:tag | @digest] [AS build-stage-name]
@@ -238,7 +238,7 @@ func (d *dispatchRequest) getImageOrStage(name string, platform *specs.Platform)
 	}
 
 	if platform == nil {
-		platform = d.builder.options.Platform
+		platform = d.builder.platform
 	}
 
 	// Windows cannot support a container with no base image unless it is LCOW.

builder/dockerfile/dispatchers_test.go

@@ -6,7 +6,6 @@ import (
 	"runtime"
 	"testing"
 
-	"github.com/containerd/containerd/platforms"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/backend"
 	"github.com/docker/docker/api/types/container"
@@ -23,8 +22,7 @@ import (
 
 func newBuilderWithMockBackend() *Builder {
 	mockBackend := &MockBackend{}
-	defaultPlatform := platforms.DefaultSpec()
-	opts := &types.ImageBuildOptions{Platform: &defaultPlatform}
+	opts := &types.ImageBuildOptions{}
 	ctx := context.Background()
 	b := &Builder{
 		options:       opts,
@@ -116,7 +114,7 @@ func TestFromScratch(t *testing.T) {
 	err := initializeStage(sb, cmd)
 
 	if runtime.GOOS == "windows" && !system.LCOWSupported() {
-		assert.Check(t, is.Error(err, "Windows does not support FROM scratch"))
+		assert.Check(t, is.Error(err, "Linux containers are not supported on this system"))
 		return
 	}
 

builder/dockerfile/internals.go

@@ -169,7 +169,7 @@ func (b *Builder) performCopy(req dispatchRequest, inst copyInstruction) error {
 		return err
 	}
 
-	imageMount, err := b.imageSources.Get(state.imageID, true, req.builder.options.Platform)
+	imageMount, err := b.imageSources.Get(state.imageID, true, req.builder.platform)
 	if err != nil {
 		return errors.Wrapf(err, "failed to get destination image %q", state.imageID)
 	}
@@ -416,7 +416,9 @@ func (b *Builder) probeAndCreate(dispatchState *dispatchState, runConfig *contai
 
 func (b *Builder) create(runConfig *container.Config) (string, error) {
 	logrus.Debugf("[BUILDER] Command to be executed: %v", runConfig.Cmd)
-	hostConfig := hostConfigFromOptions(b.options)
+
+	isWCOW := runtime.GOOS == "windows" && b.platform != nil && b.platform.OS == "windows"
+	hostConfig := hostConfigFromOptions(b.options, isWCOW)
 	container, err := b.containerManager.Create(runConfig, hostConfig)
 	if err != nil {
 		return "", err
@@ -429,7 +431,7 @@ func (b *Builder) create(runConfig *container.Config) (string, error) {
 	return container.ID, nil
 }
 
-func hostConfigFromOptions(options *types.ImageBuildOptions) *container.HostConfig {
+func hostConfigFromOptions(options *types.ImageBuildOptions, isWCOW bool) *container.HostConfig {
 	resources := container.Resources{
 		CgroupParent: options.CgroupParent,
 		CPUShares:    options.CPUShares,
@@ -457,7 +459,7 @@ func hostConfigFromOptions(options *types.ImageBuildOptions) *container.HostConf
 	// is too small for builder scenarios where many users are
 	// using RUN statements to install large amounts of data.
 	// Use 127GB as that's the default size of a VHD in Hyper-V.
-	if runtime.GOOS == "windows" && options.Platform != nil && options.Platform.OS == "windows" {
+	if isWCOW {
 		hc.StorageOpt = make(map[string]string)
 		hc.StorageOpt["size"] = "127GB"
 	}

client/image_build.go

@@ -8,8 +8,8 @@ import (
 	"net/http"
 	"net/url"
 	"strconv"
+	"strings"
 
-	"github.com/containerd/containerd/platforms"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/container"
 )
@@ -30,12 +30,6 @@ func (cli *Client) ImageBuild(ctx context.Context, buildContext io.Reader, optio
 	}
 	headers.Add("X-Registry-Config", base64.URLEncoding.EncodeToString(buf))
 
-	if options.Platform != nil {
-		if err := cli.NewVersionError("1.32", "platform"); err != nil {
-			return types.ImageBuildResponse{}, err
-		}
-		query.Set("platform", platforms.Format(*options.Platform))
-	}
 	headers.Set("Content-Type", "application/x-tar")
 
 	serverResp, err := cli.postRaw(ctx, "/build", query, buildContext, headers)
@@ -130,8 +124,11 @@ func (cli *Client) imageBuildOptionsToQuery(options types.ImageBuildOptions) (ur
 	if options.SessionID != "" {
 		query.Set("session", options.SessionID)
 	}
-	if options.Platform != nil {
-		query.Set("platform", platforms.Format(*options.Platform))
+	if options.Platform != "" {
+		if err := cli.NewVersionError("1.32", "platform"); err != nil {
+			return query, err
+		}
+		query.Set("platform", strings.ToLower(options.Platform))
 	}
 	if options.BuildID != "" {
 		query.Set("buildid", options.BuildID)