Add metadata-file flag

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

commands/bake.go

@@ -10,6 +10,7 @@ import (
 	"github.com/docker/buildx/build"
 	"github.com/docker/buildx/util/progress"
 	"github.com/docker/cli/cli/command"
+	"github.com/docker/docker/pkg/ioutils"
 	"github.com/moby/buildkit/util/appcontext"
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
@@ -90,7 +91,7 @@ func runBake(dockerCli command.Cli, targets []string, in bakeOptions) (err error
 	}
 
 	if in.printOnly {
-		dt, err := json.MarshalIndent(map[string]map[string]*bake.Target{"target": m}, "", "   ")
+		dt, err := json.MarshalIndent(map[string]map[string]*bake.Target{"target": m}, "", "  ")
 		if err != nil {
 			return err
 		}
@@ -108,7 +109,25 @@ func runBake(dockerCli command.Cli, targets []string, in bakeOptions) (err error
 		return err
 	}
 
-	_, err = build.Build(ctx, dis, bo, dockerAPI(dockerCli), dockerCli.ConfigFile(), printer)
+	resp, err := build.Build(ctx, dis, bo, dockerAPI(dockerCli), dockerCli.ConfigFile(), printer)
+	if err != nil {
+		return err
+	}
+
+	if len(in.metadataFile) > 0 && resp != nil {
+		mdata := map[string]map[string]string{}
+		for k, r := range resp {
+			mdata[k] = r.ExporterResponse
+		}
+		mdatab, err := json.MarshalIndent(mdata, "", "  ")
+		if err != nil {
+			return err
+		}
+		if err := ioutils.AtomicWriteFile(in.metadataFile, mdatab, 0644); err != nil {
+			return err
+		}
+	}
+
 	return err
 }
 

commands/build.go

@@ -2,6 +2,7 @@ package commands
 
 import (
 	"context"
+	"encoding/json"
 	"os"
 	"path/filepath"
 	"strings"
@@ -12,6 +13,7 @@ import (
 	"github.com/docker/buildx/util/progress"
 	"github.com/docker/cli/cli"
 	"github.com/docker/cli/cli/command"
+	"github.com/docker/docker/pkg/ioutils"
 	"github.com/moby/buildkit/client"
 	"github.com/moby/buildkit/session/auth/authprovider"
 	"github.com/moby/buildkit/util/appcontext"
@@ -21,6 +23,8 @@ import (
 	"github.com/spf13/pflag"
 )
 
+const defaultTargetName = "default"
+
 type buildOptions struct {
 	commonOptions
 	contextPath    string
@@ -64,10 +68,11 @@ type buildOptions struct {
 }
 
 type commonOptions struct {
-	builder  string
-	noCache  *bool
-	progress string
-	pull     *bool
+	builder      string
+	noCache      *bool
+	progress     string
+	pull         *bool
+	metadataFile string
 	// golangci-lint#826
 	// nolint:structcheck
 	exportPush bool
@@ -200,10 +205,10 @@ func runBuild(dockerCli command.Cli, in buildOptions) error {
 		contextPathHash = in.contextPath
 	}
 
-	return buildTargets(ctx, dockerCli, map[string]build.Options{"default": opts}, in.progress, contextPathHash, in.builder)
+	return buildTargets(ctx, dockerCli, map[string]build.Options{defaultTargetName: opts}, in.progress, contextPathHash, in.builder, in.metadataFile)
 }
 
-func buildTargets(ctx context.Context, dockerCli command.Cli, opts map[string]build.Options, progressMode, contextPathHash, instance string) error {
+func buildTargets(ctx context.Context, dockerCli command.Cli, opts map[string]build.Options, progressMode, contextPathHash, instance string, metadataFile string) error {
 	dis, err := getInstanceOrDefault(ctx, dockerCli, instance, contextPathHash)
 	if err != nil {
 		return err
@@ -213,11 +218,24 @@ func buildTargets(ctx context.Context, dockerCli command.Cli, opts map[string]bu
 	defer cancel()
 	printer := progress.NewPrinter(ctx2, os.Stderr, progressMode)
 
-	_, err = build.Build(ctx, dis, opts, dockerAPI(dockerCli), dockerCli.ConfigFile(), printer)
+	resp, err := build.Build(ctx, dis, opts, dockerAPI(dockerCli), dockerCli.ConfigFile(), printer)
 	err1 := printer.Wait()
 	if err == nil {
 		err = err1
 	}
+	if err != nil {
+		return err
+	}
+
+	if len(metadataFile) > 0 && resp != nil {
+		mdatab, err := json.MarshalIndent(resp[defaultTargetName].ExporterResponse, "", "  ")
+		if err != nil {
+			return err
+		}
+		if err := ioutils.AtomicWriteFile(metadataFile, mdatab, 0644); err != nil {
+			return err
+		}
+	}
 
 	return err
 }
@@ -333,6 +351,7 @@ func commonBuildFlags(options *commonOptions, flags *pflag.FlagSet) {
 	flags.StringVar(&options.progress, "progress", defaultProgress, "Set type of progress output (auto, plain, tty). Use plain to show container output")
 
 	options.pull = flags.Bool("pull", false, "Always attempt to pull a newer version of the image")
+	flags.StringVar(&options.metadataFile, "metadata-file", "", "Write build result metadata to the file")
 }
 
 func listToMap(values []string, defaultEnv bool) map[string]string {

docs/reference/buildx_bake.md

@@ -18,6 +18,7 @@ Build from a file
 | `--builder string` | Override the configured builder instance |
 | [`-f`](#file), [`--file stringArray`](#file) | Build definition file |
 | `--load` | Shorthand for --set=*.output=type=docker |
+| `--metadata-file string` | Write build result metadata to the file |
 | [`--no-cache`](#no-cache) | Do not use cache when building the image |
 | [`--print`](#print) | Print the options without building |
 | [`--progress string`](#progress) | Set type of progress output (auto, plain, tty). Use plain to show container output |

docs/reference/buildx_build.md

@@ -25,6 +25,7 @@ Start a build
 | `--iidfile string` | Write the image ID to the file |
 | `--label stringArray` | Set metadata for an image |
 | [`--load`](#load) | Shorthand for --output=type=docker |
+| `--metadata-file string` | Write build result metadata to the file |
 | `--network string` | Set the networking mode for the RUN instructions during build |
 | `--no-cache` | Do not use cache when building the image |
 | [`-o`](#output), [`--output stringArray`](#output) | Output destination (format: type=local,dest=path) |