Add Docker exporter

README.md

@@ -123,7 +123,14 @@ If credentials are required, `buildctl` will attempt to read Docker configuratio
 buildctl build ... --exporter=local --exporter-opt output=path/to/output-dir
 ```
 
-#### Exporting OCI Image Format tarball to client
+##### Exporting build result to Docker
+
+```
+# exported tarball is also compatible with OCI spec
+buildctl build ... --exporter=docker --exporter-opt name=myimage | docker load
+```
+
+##### Exporting OCI Image Format tarball to client
 
 ```
 buildctl build ... --exporter=oci --exporter-opt output=path/to/output.tar

client/client_test.go

@@ -275,50 +275,80 @@ func testOCIExporter(t *testing.T, sb integration.Sandbox) {
 	def, err := st.Marshal()
 	require.NoError(t, err)
 
-	destDir, err := ioutil.TempDir("", "buildkit")
-	require.NoError(t, err)
-	defer os.RemoveAll(destDir)
-
-	out := filepath.Join(destDir, "out.tar")
-
-	err = c.Solve(context.TODO(), def, SolveOpt{
-		Exporter: ExporterOCI,
-		ExporterAttrs: map[string]string{
-			"output": out,
-		},
-	}, nil)
-	require.NoError(t, err)
-
-	dt, err := ioutil.ReadFile(out)
-	require.NoError(t, err)
-
-	m, err := readTarToMap(dt, false)
-	require.NoError(t, err)
-
-	_, ok := m["oci-layout"]
-	require.True(t, ok)
-
-	var index ocispec.Index
-	err = json.Unmarshal(m["index.json"].data, &index)
-	require.NoError(t, err)
-	require.Equal(t, 2, index.SchemaVersion)
-	require.Equal(t, 1, len(index.Manifests))
-
-	var mfst ocispec.Manifest
-	err = json.Unmarshal(m["blobs/sha256/"+index.Manifests[0].Digest.Hex()].data, &mfst)
-	require.NoError(t, err)
-	require.Equal(t, 2, len(mfst.Layers))
+	for _, exp := range []string{ExporterOCI, ExporterDocker} {
+
+		destDir, err := ioutil.TempDir("", "buildkit")
+		require.NoError(t, err)
+		defer os.RemoveAll(destDir)
+
+		out := filepath.Join(destDir, "out.tar")
+		target := "example.com/buildkit/testoci:latest"
+
+		err = c.Solve(context.TODO(), def, SolveOpt{
+			Exporter: exp,
+			ExporterAttrs: map[string]string{
+				"output": out,
+				"name":   target,
+			},
+		}, nil)
+		require.NoError(t, err)
+
+		dt, err := ioutil.ReadFile(out)
+		require.NoError(t, err)
+
+		m, err := readTarToMap(dt, false)
+		require.NoError(t, err)
+
+		_, ok := m["oci-layout"]
+		require.True(t, ok)
+
+		var index ocispec.Index
+		err = json.Unmarshal(m["index.json"].data, &index)
+		require.NoError(t, err)
+		require.Equal(t, 2, index.SchemaVersion)
+		require.Equal(t, 1, len(index.Manifests))
+
+		var mfst ocispec.Manifest
+		err = json.Unmarshal(m["blobs/sha256/"+index.Manifests[0].Digest.Hex()].data, &mfst)
+		require.NoError(t, err)
+		require.Equal(t, 2, len(mfst.Layers))
+
+		var ociimg ocispec.Image
+		err = json.Unmarshal(m["blobs/sha256/"+mfst.Config.Digest.Hex()].data, &ociimg)
+		require.NoError(t, err)
+		require.Equal(t, "layers", ociimg.RootFS.Type)
+		require.Equal(t, 2, len(ociimg.RootFS.DiffIDs))
+
+		_, ok = m["blobs/sha256/"+mfst.Layers[0].Digest.Hex()]
+		require.True(t, ok)
+		_, ok = m["blobs/sha256/"+mfst.Layers[1].Digest.Hex()]
+		require.True(t, ok)
+
+		if exp != ExporterDocker {
+			continue
+		}
 
-	var ociimg ocispec.Image
-	err = json.Unmarshal(m["blobs/sha256/"+mfst.Config.Digest.Hex()].data, &ociimg)
-	require.NoError(t, err)
-	require.Equal(t, "layers", ociimg.RootFS.Type)
-	require.Equal(t, 2, len(ociimg.RootFS.DiffIDs))
+		var dockerMfst []struct {
+			Config   string
+			RepoTags []string
+			Layers   []string
+		}
+		err = json.Unmarshal(m["manifest.json"].data, &dockerMfst)
+		require.NoError(t, err)
+		require.Equal(t, 1, len(dockerMfst))
+
+		_, ok = m[dockerMfst[0].Config]
+		require.True(t, ok)
+		require.Equal(t, 2, len(dockerMfst[0].Layers))
+		require.Equal(t, 1, len(dockerMfst[0].RepoTags))
+		require.Equal(t, target, dockerMfst[0].RepoTags[0])
+
+		for _, l := range dockerMfst[0].Layers {
+			_, ok := m[l]
+			require.True(t, ok)
+		}
 
-	_, ok = m["blobs/sha256/"+mfst.Layers[0].Digest.Hex()]
-	require.True(t, ok)
-	_, ok = m["blobs/sha256/"+mfst.Layers[1].Digest.Hex()]
-	require.True(t, ok)
+	}
 }
 
 func testBuildPushAndValidate(t *testing.T, sb integration.Sandbox) {

client/exporters.go

@@ -1,9 +1,10 @@
 package client
 
 const (
-	ExporterImage = "image"
-	ExporterLocal = "local"
-	ExporterOCI   = "oci"
+	ExporterImage  = "image"
+	ExporterLocal  = "local"
+	ExporterOCI    = "oci"
+	ExporterDocker = "docker"
 
 	exporterLocalOutputDir = "output"
 	exporterOCIDestination = "output"

client/solve.go

@@ -79,7 +79,7 @@ func (c *Client) Solve(ctx context.Context, def *llb.Definition, opt SolveOpt, s
 			return errors.Errorf("output directory is required for local exporter")
 		}
 		s.Allow(filesync.NewFSSyncTarget(outputDir))
-	case ExporterOCI:
+	case ExporterOCI, ExporterDocker:
 		outputFile, ok := opt.ExporterAttrs[exporterOCIDestination]
 		if ok {
 			fi, err := os.Stat(outputFile)
@@ -91,7 +91,7 @@ func (c *Client) Solve(ctx context.Context, def *llb.Definition, opt SolveOpt, s
 			}
 		} else {
 			if _, err := console.ConsoleFromFile(os.Stdout); err == nil {
-				return errors.Errorf("output file is required for OCI exporter. refusing to write to console")
+				return errors.Errorf("output file is required for %s exporter. refusing to write to console", opt.Exporter)
 			}
 			outputFile = ""
 		}