feat: add build-context support.

pkg/build/build.go

@@ -171,6 +171,19 @@ func Build(ctx context.Context, opts *BOpts) error {
 	for k, v := range opts.Labels {
 		solveOpt.FrontendAttrs["label:"+k] = v
 	}
+	for name, ref := range opts.BuildContexts {
+		switch strings.SplitN(ref, ":", 2)[0] {
+		case "docker-image", "git", "http", "https":
+			solveOpt.FrontendAttrs["context:"+name] = ref
+		case "oci-layout":
+			// oci-layout requires custom handling as it needs to load the layout data from the client
+			// not setting solveOpt.FrontendAttrs["context:"+name] here for the frontend can handle it because namedcontext will resolve
+			solveOpt.OCIStores[name] = opts.ContentStore
+		default: // bare path → local context
+			solveOpt.FrontendAttrs["context:"+name] = "local:" + name
+		}
+	}
+
 	solveOpt.Frontend = "dockerfile.v1"
 
 	if len(opts.SSH) > 0 {

pkg/build/buildopts.go

@@ -53,8 +53,8 @@ const (
 	KeyProgress = "progress"
 	// When present, disables layer caching.
 	KeyNoCache = "no-cache"
-	// Build context directory path.
-	KeyContext = "context"
+	// Build base context directory path.
+	KeyContextDirectory = "context"
 	// Dockerfile stage to build up to.
 	KeyTarget = "target"
 	// Key=value metadata labels to apply to the image.
@@ -73,6 +73,8 @@ const (
 	KeyOutput = "outputs"
 	// Unique build identifier.
 	KeyBuildID = "build-id"
+	// Additional Build contexts (--build-context).
+	KeyBuildContext = "build-context"
 )
 
 const (
@@ -103,6 +105,7 @@ type BOpts struct {
 	Outputs        []string
 	Labels         map[string]string
 	ProgressWriter progresswriter.Writer
+	BuildContexts  map[string]string
 
 	ContentStore *content.ContentStoreProxy
 	Resolver     *resolver.ResolverProxy
@@ -169,7 +172,7 @@ func NewBuildOpts(ctx context.Context, basePath string, contextMap map[string][]
 	}
 
 	ctxDir := "."
-	if c, ok := first(KeyContext); ok {
+	if c, ok := first(KeyContextDirectory); ok {
 		ctxDir = c
 	}
 
@@ -272,6 +275,7 @@ func NewBuildOpts(ctx context.Context, basePath string, contextMap map[string][]
 
 	labels := mapExtract(KeyLabels)
 	buildArgs := mapExtract(KeyBuildArgs)
+	buildContexts := mapExtract(KeyBuildContext)
 	secrets, err := mapExtractB64(KeySecrets)
 	if err != nil {
 		return nil, err
@@ -350,7 +354,7 @@ func NewBuildOpts(ctx context.Context, basePath string, contextMap map[string][]
 		}
 	}
 
-	fssyncProxy, err := fssync.NewFSSyncProxy(".", basePath, addedGlobs, dockerfileBytes, dockerignoreBytes)
+	fssyncProxy, err := fssync.NewFSSyncProxy(ctxDir, basePath, addedGlobs, dockerfileBytes, dockerignoreBytes, buildContexts)
 	if err != nil {
 		return nil, err
 	}
@@ -383,6 +387,7 @@ func NewBuildOpts(ctx context.Context, basePath string, contextMap map[string][]
 		CacheOut:       cacheOut,
 		Outputs:        outputs,
 		basePath:       filepath.Join(basePath, buildID),
+		BuildContexts:  buildContexts,
 	}
 
 	return bopts, nil

pkg/build/frontend.go

@@ -29,6 +29,7 @@ import (
 	"github.com/containerd/platforms"
 	dref "github.com/distribution/reference"
 
+	"github.com/apple/container-builder-shim/pkg/build/utils"
 	"github.com/moby/buildkit/client/llb"
 	"github.com/moby/buildkit/client/llb/sourceresolver"
 	"github.com/moby/buildkit/exporter/containerimage/exptypes"
@@ -42,8 +43,6 @@ import (
 	"github.com/moby/buildkit/util/progress/progresswriter"
 	ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/sirupsen/logrus"
-
-	"github.com/apple/container-builder-shim/pkg/build/utils"
 )
 
 func frontend(ctx context.Context, c gateway.Client) (*gateway.Result, error) {
@@ -131,6 +130,79 @@ func resolveStates(ctx context.Context, bopts *BOpts, platform ocispecs.Platform
 	stateLock := sync.Mutex{}
 
 	resolveSource := func(resolvedBaseStageName string, sourcePlatform ocispecs.Platform) error {
+
+		saveState := func(img []byte, fqdn string, ref string, storeName string, opts ...llb.OCILayoutOption) error {
+			opts = append(opts, llb.Platform(sourcePlatform))
+			opts = append(opts, llb.OCIStore("", storeName))
+
+			st := llb.OCILayout(fqdn, opts...)
+
+			st, err = st.WithImageConfig(img)
+			if err != nil {
+				return err
+			}
+
+			named, err := dref.ParseNormalizedNamed(ref)
+			if err != nil {
+				return fmt.Errorf("invalid context name %s %v", ref, err)
+			}
+			// pname constructs a platform-qualified image reference in the format buildkit requires for digest resolution
+			name := strings.TrimSuffix(dref.FamiliarString(named), ":latest")
+			pname := name + "::" + platforms.FormatAll(platforms.Normalize(sourcePlatform))
+
+			imgMetaMap := map[string][]byte{
+				exptypes.ExporterImageConfigKey: img,
+			}
+			imgMeta, err := json.Marshal(imgMetaMap)
+			if err != nil {
+				return err
+			}
+
+			stateLock.Lock()
+			states[pname] = stateMeta{
+				state:   st.Platform(sourcePlatform),
+				imgMeta: imgMeta,
+			}
+			stateLock.Unlock()
+			return nil
+		}
+
+		// handle build context
+		if val, ok := bopts.BuildContexts[resolvedBaseStageName]; ok {
+			// oci-layout requires custom handling as namedContext cannot load from client correctly
+			if strings.SplitN(val, ":", 2)[0] != "oci-layout" {
+				return nil
+			}
+			// passing in "oci-layout" as they are so client side knows that it is oci from build-context
+			resolverOpts := sourceresolver.Opt{}
+			resolverOpts.ImageOpt = &sourceresolver.ResolveImageOpt{
+				Platform:    &sourcePlatform,
+				ResolveMode: llb.ResolveModePreferLocal.String(),
+			}
+			resolverOpts.OCILayoutOpt = &sourceresolver.ResolveOCILayoutOpt{
+				Store: sourceresolver.ResolveImageConfigOptStore{
+					StoreID:   resolvedBaseStageName,
+					SessionID: "",
+				},
+			}
+			_, digest, img, err := bopts.Resolver.ResolveImageConfig(ctx, val, resolverOpts)
+			if err != nil {
+				if err == reference.ErrObjectRequired {
+					return nil
+				}
+				return err
+			}
+
+			// not using the returning `ref` here as the `ref` will be the local path like /User/path/to/oci-layout
+			// However, when using resolvedBaseStageName directly (ex: deps),
+			// and if we don't add some dummy host like "docker.io/library/".
+			// we will get an error like following
+			// Error: unknown: "failed to solve: failed to load cache key: parse "dummy://deps@sha256:xxx": invalid port ":xxx" after host"
+			ref := resolvedBaseStageName
+			fqdn := "docker.io/library/" + ref + "@" + digest.String()
+			return saveState(img, fqdn, ref, resolvedBaseStageName, llb.WithCustomName("[context "+resolvedBaseStageName+"] OCI load from client"))
+		}
+
 		if strings.EqualFold(resolvedBaseStageName, "scratch") || strings.EqualFold(resolvedBaseStageName, "context") {
 			return nil
 		}
@@ -152,7 +224,7 @@ func resolveStates(ctx context.Context, bopts *BOpts, platform ocispecs.Platform
 		}
 		resolverOpts.OCILayoutOpt = &sourceresolver.ResolveOCILayoutOpt{
 			Store: sourceresolver.ResolveImageConfigOptStore{
-				StoreID:   "container",
+				StoreID:   KeyContentStoreName,
 				SessionID: "",
 			},
 		}
@@ -175,31 +247,7 @@ func resolveStates(ctx context.Context, bopts *BOpts, platform ocispecs.Platform
 		if _, ok := ref.(dref.Digested); !ok {
 			fqdn += "@" + digest.String()
 		}
-		st := llb.OCILayout(fqdn, llb.OCIStore("", "container"), llb.Platform(sourcePlatform))
-
-		named, err := dref.ParseNormalizedNamed(ref.String())
-		if err != nil {
-			return fmt.Errorf("invalid context name %s %v", ref.String(), err)
-		}
-		// pname constructs a platform-qualified image reference in the format buildkit requires for digest resolution
-		name := strings.TrimSuffix(dref.FamiliarString(named), ":latest")
-		pname := name + "::" + platforms.FormatAll(platforms.Normalize(sourcePlatform))
-
-		imgMetaMap := map[string][]byte{
-			exptypes.ExporterImageConfigKey: img,
-		}
-		imgMeta, err := json.Marshal(imgMetaMap)
-		if err != nil {
-			return err
-		}
-
-		stateLock.Lock()
-		states[pname] = stateMeta{
-			state:   st.Platform(sourcePlatform),
-			imgMeta: imgMeta,
-		}
-		stateLock.Unlock()
-		return nil
+		return saveState(img, fqdn, ref.String(), KeyContentStoreName)
 	}
 
 	for i, stage := range stages {

pkg/fssync/fssync.go

@@ -58,10 +58,12 @@ type FSSyncProxy struct {
 
 	dockerfile   []byte
 	dockerignore []byte
+
+	buildContexts map[string]string
 }
 
 func NewFSSyncProxy(contextDir string, basePath string, addedGlobs []string,
-	dockerfile []byte, dockerignore []byte) (*FSSyncProxy, error) {
+	dockerfile []byte, dockerignore []byte, buildContexts map[string]string) (*FSSyncProxy, error) {
 
 	f := new(FSSyncProxy)
 	f.contextDir = contextDir
@@ -70,6 +72,7 @@ func NewFSSyncProxy(contextDir string, basePath string, addedGlobs []string,
 
 	f.dockerfile = dockerfile
 	f.dockerignore = dockerignore
+	f.buildContexts = buildContexts
 	return f, nil
 }
 

pkg/fssync/walk.go

@@ -107,11 +107,17 @@ func (f *FS) Walk(ctx context.Context, target string, fn fs.WalkDirFunc) error {
 	if followPaths == "" {
 		followPaths = strings.Join(f.proxy.addedGlobs, ",")
 	}
+	root := f.root
+	if walkMeta.DirName != "" && walkMeta.DirName != "context" && walkMeta.DirName != "scratch" {
+		if val, ok := f.proxy.buildContexts[walkMeta.DirName]; ok {
+			root = val
+		}
+	}
 
 	packet := &api.BuildTransfer{
 		Id:        id,
 		Direction: api.TransferDirection_OUTOF,
-		Source:    &f.root,
+		Source:    &root,
 		Metadata: map[string]string{
 			"os":               "linux",
 			"stage":            "fssync",