Add builder OCI layout build context

Signed-off-by: Austin Vazquez <macedonv@amazon.com>

cmd/nerdctl/builder_build_linux_test.go

@@ -0,0 +1,55 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package main
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/containerd/nerdctl/v2/pkg/testutil"
+	"gotest.tools/v3/assert"
+)
+
+func TestBuildContextWithOCILayout(t *testing.T) {
+	testutil.DockerIncompatible(t)
+	testutil.RequiresBuild(t)
+	testutil.RegisterBuildCacheCleanup(t)
+
+	base := testutil.NewBase(t)
+	imageName := testutil.Identifier(t)
+	t.Cleanup(func() { base.Cmd("rmi", imageName) })
+
+	dockerfile := fmt.Sprintf(`FROM %s
+LABEL layer=oci-layout
+CMD ["echo", "nerdctl-build-oci-layout-build-context"]`, testutil.CommonImage)
+	buildCtx := createBuildContext(t, dockerfile)
+
+	tarPath := fmt.Sprintf("%s/%s", buildCtx, "test.tar")
+	base.Cmd("build", buildCtx, fmt.Sprintf("--output=type=oci,dest=%s", tarPath)).Run()
+
+	ociLayoutDir := t.TempDir()
+
+	err := extractTarFile(ociLayoutDir, tarPath)
+	assert.NilError(t, err)
+
+	ociLayout := "test"
+	dockerfile = fmt.Sprintf(`FROM %s
+CMD ["echo", "nerdctl-test-build-context-oci-layout"]`, ociLayout)
+	buildCtx = createBuildContext(t, dockerfile)
+
+	base.Cmd("build", buildCtx, fmt.Sprintf("--build-context=%s=oci-layout://%s", ociLayout, ociLayoutDir), "-t", imageName).AssertOK()
+}

docs/command-reference.md

@@ -708,7 +708,7 @@ Flags:
 - :nerd_face: `--ipfs`: Build image with pulling base images from IPFS. See [`ipfs.md`](./ipfs.md) for details.
 - :whale: `--label`: Set metadata for an image
 - :whale: `--network=(default|host|none)`: Set the networking mode for the RUN instructions during build.(compatible with `buildctl build`)
-- :whale: --build-context: Set additional contexts for build (e.g. dir2=/path/to/dir2, myorg/myapp=docker-image://path/to/myorg/myapp)
+- :whale: `--build-context`: Set additional contexts for build (e.g. dir2=/path/to/dir2, myorg/myapp=docker-image://path/to/myorg/myapp)
 
 Unimplemented `docker build` flags: `--add-host`, `--squash`
 

pkg/cmd/builder/build.go

@@ -36,6 +36,7 @@ import (
 	"github.com/containerd/errdefs"
 	"github.com/containerd/log"
 	"github.com/containerd/platforms"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 
 	"github.com/containerd/nerdctl/v2/pkg/api/types"
 	"github.com/containerd/nerdctl/v2/pkg/buildkitutil"
@@ -300,6 +301,16 @@ func generateBuildctlArgs(ctx context.Context, client *containerd.Client, option
 			continue
 		}
 
+		if isOCILayout := strings.HasPrefix(v, "oci-layout://"); isOCILayout {
+			args, err := parseBuildContextFromOCILayout(k, v)
+			if err != nil {
+				return "", nil, false, "", nil, nil, err
+			}
+
+			buildctlArgs = append(buildctlArgs, args...)
+			continue
+		}
+
 		path, err := filepath.Abs(v)
 		if err != nil {
 			return "", nil, false, "", nil, nil, err
@@ -534,3 +545,61 @@ func parseContextNames(values []string) (map[string]string, error) {
 	}
 	return result, nil
 }
+
+var (
+	errOCILayoutPrefixNotFound = errors.New("OCI layout prefix not found")
+	errOCILayoutEmptyDigest    = errors.New("OCI layout cannot have empty digest")
+)
+
+func parseBuildContextFromOCILayout(name, path string) ([]string, error) {
+	path, found := strings.CutPrefix(path, "oci-layout://")
+	if !found {
+		return []string{}, errOCILayoutPrefixNotFound
+	}
+
+	abspath, err := filepath.Abs(path)
+	if err != nil {
+		return []string{}, err
+	}
+
+	ociIndex, err := readOCIIndexFromPath(abspath)
+	if err != nil {
+		return []string{}, err
+	}
+
+	var digest string
+	for _, manifest := range ociIndex.Manifests {
+		if manifest.MediaType == ocispec.MediaTypeImageManifest {
+			digest = manifest.Digest.String()
+		}
+	}
+
+	if digest == "" {
+		return []string{}, errOCILayoutEmptyDigest
+	}
+
+	return []string{
+		fmt.Sprintf("--oci-layout=parent-image-key=%s", abspath),
+		fmt.Sprintf("--opt=context:%s=oci-layout:parent-image-key@%s", name, digest),
+	}, nil
+}
+
+func readOCIIndexFromPath(path string) (*ocispec.Index, error) {
+	ociIndexJSONFile, err := os.Open(path + "/index.json")
+	if err != nil {
+		return nil, err
+	}
+	defer ociIndexJSONFile.Close()
+
+	rawBytes, err := io.ReadAll(ociIndexJSONFile)
+	if err != nil {
+		return nil, err
+	}
+
+	var ociIndex *ocispec.Index
+	err = json.Unmarshal(rawBytes, &ociIndex)
+	if err != nil {
+		return nil, err
+	}
+	return ociIndex, nil
+}

pkg/cmd/builder/build_test.go

@@ -187,3 +187,34 @@ func TestIsBuildPlatformDefault(t *testing.T) {
 		})
 	}
 }
+
+func TestParseBuildctlArgsForOCILayout(t *testing.T) {
+	tests := []struct {
+		name          string
+		ociLayoutName string
+		ociLayoutPath string
+		expectedArgs  []string
+		expectedErr   error
+	}{
+		{
+			name:          "PrefixNotFoundError",
+			ociLayoutName: "test",
+			ociLayoutPath: "/tmp/oci-layout/",
+			expectedArgs:  []string{},
+			expectedErr:   errOCILayoutPrefixNotFound,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			args, err := parseBuildContextFromOCILayout(test.ociLayoutName, test.ociLayoutPath)
+			if test.expectedErr == nil {
+				assert.NilError(t, err)
+			} else {
+				assert.ErrorIs(t, err, test.expectedErr)
+			}
+			assert.Equal(t, len(args), len(test.expectedArgs))
+			assert.DeepEqual(t, args, test.expectedArgs)
+		})
+	}
+}