Merge pull request #3235 from jsternberg/dap-handler

dap: add debug adapter implementation

build/build.go

@@ -313,9 +313,12 @@ func toRepoOnly(in string) (string, error) {
 	return strings.Join(out, ","), nil
 }
 
-type Handler struct {
-	Evaluate func(ctx context.Context, c gateway.Client, res *gateway.Result) error
+type (
+	EvaluateFunc func(ctx context.Context, name string, c gateway.Client, res *gateway.Result) error
+	Handler      struct {
+		Evaluate EvaluateFunc
 	}
+)
 
 func Build(ctx context.Context, nodes []builder.Node, opts map[string]Options, docker *dockerutil.Client, cfg *confutil.Config, w progress.Writer) (resp map[string]*client.SolveResponse, err error) {
 	return BuildWithResultHandler(ctx, nodes, opts, docker, cfg, w, nil)
@@ -510,12 +513,25 @@ func BuildWithResultHandler(ctx context.Context, nodes []builder.Node, opts map[
 						rKey := resultKey(dp.driverIndex, k)
 						results.Set(rKey, res)
 
+						forceEval := false
 						if children := childTargets[rKey]; len(children) > 0 {
-							if err := waitForChildren(ctx, bh, c, res, results, children); err != nil {
+							// wait for the child targets to register their LLB before evaluating
+							_, err := results.Get(ctx, children...)
+							if err != nil {
 								return nil, err
 							}
-						} else if bh != nil && bh.Evaluate != nil {
-							if err := bh.Evaluate(ctx, c, res); err != nil {
+							forceEval = true
+						}
+
+						// invoke custom evaluate handler if it is present
+						if bh != nil && bh.Evaluate != nil {
+							if err := bh.Evaluate(ctx, k, c, res); err != nil {
+								return nil, err
+							}
+						} else if forceEval {
+							if err := res.EachRef(func(ref gateway.Reference) error {
+								return ref.Evaluate(ctx)
+							}); err != nil {
 								return nil, err
 							}
 						}
@@ -1199,29 +1215,6 @@ func solve(ctx context.Context, c gateway.Client, req gateway.SolveRequest) (*ga
 	return res, nil
 }
 
-func waitForChildren(ctx context.Context, bh *Handler, c gateway.Client, res *gateway.Result, results *waitmap.Map, children []string) error {
-	// wait for the child targets to register their LLB before evaluating
-	_, err := results.Get(ctx, children...)
-	if err != nil {
-		return err
-	}
-	// we need to wait until the child targets have completed before we can release
-	eg, ctx := errgroup.WithContext(ctx)
-	eg.Go(func() error {
-		if bh != nil && bh.Evaluate != nil {
-			return bh.Evaluate(ctx, c, res)
-		}
-		return res.EachRef(func(ref gateway.Reference) error {
-			return ref.Evaluate(ctx)
-		})
-	})
-	eg.Go(func() error {
-		_, err := results.Get(ctx, children...)
-		return err
-	})
-	return eg.Wait()
-}
-
 func catchFrontendError(retErr, frontendErr *error) {
 	*frontendErr = *retErr
 	if errors.Is(*retErr, ErrRestart) {

build/invoke.go

@@ -14,18 +14,18 @@ import (
 )
 
 type InvokeConfig struct {
-	Entrypoint []string
-	Cmd        []string
-	NoCmd      bool
-	Env        []string
-	User       string
-	NoUser     bool
-	Cwd        string
-	NoCwd      bool
-	Tty        bool
-	Rollback   bool
-	Initial    bool
-	SuspendOn  SuspendOn
+	Entrypoint []string  `json:"entrypoint,omitempty"`
+	Cmd        []string  `json:"cmd,omitempty"`
+	NoCmd      bool      `json:"noCmd,omitempty"`
+	Env        []string  `json:"env,omitempty"`
+	User       string    `json:"user,omitempty"`
+	NoUser     bool      `json:"noUser,omitempty"`
+	Cwd        string    `json:"cwd,omitempty"`
+	NoCwd      bool      `json:"noCwd,omitempty"`
+	Tty        bool      `json:"tty,omitempty"`
+	Rollback   bool      `json:"rollback,omitempty"`
+	Initial    bool      `json:"initial,omitempty"`
+	SuspendOn  SuspendOn `json:"suspendOn,omitempty"`
 }
 
 func (cfg *InvokeConfig) NeedsDebug(err error) bool {
@@ -43,6 +43,18 @@ func (s SuspendOn) DebugEnabled(err error) bool {
 	return err != nil || s == SuspendAlways
 }
 
+func (s *SuspendOn) UnmarshalText(text []byte) error {
+	switch string(text) {
+	case "error":
+		*s = SuspendError
+	case "always":
+		*s = SuspendAlways
+	default:
+		return errors.Errorf("unknown suspend name: %s", string(text))
+	}
+	return nil
+}
+
 type Container struct {
 	cancelOnce      sync.Once
 	containerCancel func(error)

build/result.go

@@ -16,7 +16,7 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
-// NewResultHandle stores a gateway client, gateway result, and the error from
+// NewResultHandle stores a gateway client, gateway reference, and the error from
 // an evaluate call if it is present.
 //
 // This ResultHandle can be used to execute additional build steps in the same
@@ -24,9 +24,10 @@ import (
 // failures and successes.
 //
 // If the returned ResultHandle is not nil, the caller must call Done() on it.
-func NewResultHandle(ctx context.Context, c gateway.Client, res *gateway.Result, err error) *ResultHandle {
+func NewResultHandle(ctx context.Context, c gateway.Client, ref gateway.Reference, meta map[string][]byte, err error) *ResultHandle {
 	rCtx := &ResultHandle{
-		res:      res,
+		ref:      ref,
+		meta:     meta,
 		gwClient: c,
 	}
 	if err != nil && !errors.As(err, &rCtx.solveErr) {
@@ -37,8 +38,9 @@ func NewResultHandle(ctx context.Context, c gateway.Client, res *gateway.Result,
 
 // ResultHandle is a build result with the client that built it.
 type ResultHandle struct {
-	res      *gateway.Result
+	ref      gateway.Reference
 	solveErr *errdefs.SolveError
+	meta     map[string][]byte
 	gwClient gateway.Client
 
 	doneOnce sync.Once
@@ -74,9 +76,9 @@ func (r *ResultHandle) NewContainer(ctx context.Context, cfg *InvokeConfig) (gat
 }
 
 func (r *ResultHandle) getContainerConfig(cfg *InvokeConfig) (containerCfg gateway.NewContainerRequest, _ error) {
-	if r.res != nil && r.solveErr == nil {
+	if r.ref != nil && r.solveErr == nil {
 		logrus.Debugf("creating container from successful build")
-		ccfg, err := containerConfigFromResult(r.res, cfg)
+		ccfg, err := containerConfigFromResult(r.ref, cfg)
 		if err != nil {
 			return containerCfg, err
 		}
@@ -94,9 +96,9 @@ func (r *ResultHandle) getContainerConfig(cfg *InvokeConfig) (containerCfg gatew
 
 func (r *ResultHandle) getProcessConfig(cfg *InvokeConfig, stdin io.ReadCloser, stdout io.WriteCloser, stderr io.WriteCloser) (_ gateway.StartRequest, err error) {
 	processCfg := newStartRequest(stdin, stdout, stderr)
-	if r.res != nil && r.solveErr == nil {
+	if r.ref != nil && r.solveErr == nil {
 		logrus.Debugf("creating container from successful build")
-		if err := populateProcessConfigFromResult(&processCfg, r.res, cfg); err != nil {
+		if err := populateProcessConfigFromResult(&processCfg, r.meta, cfg); err != nil {
 			return processCfg, err
 		}
 	} else {
@@ -108,20 +110,11 @@ func (r *ResultHandle) getProcessConfig(cfg *InvokeConfig, stdin io.ReadCloser,
 	return processCfg, nil
 }
 
-func containerConfigFromResult(res *gateway.Result, cfg *InvokeConfig) (*gateway.NewContainerRequest, error) {
+func containerConfigFromResult(ref gateway.Reference, cfg *InvokeConfig) (*gateway.NewContainerRequest, error) {
 	if cfg.Initial {
 		return nil, errors.Errorf("starting from the container from the initial state of the step is supported only on the failed steps")
 	}
 
-	ps, err := exptypes.ParsePlatforms(res.Metadata)
-	if err != nil {
-		return nil, err
-	}
-	ref, ok := res.FindRef(ps.Platforms[0].ID)
-	if !ok {
-		return nil, errors.Errorf("no reference found")
-	}
-
 	return &gateway.NewContainerRequest{
 		Mounts: []gateway.Mount{
 			{
@@ -133,8 +126,8 @@ func containerConfigFromResult(res *gateway.Result, cfg *InvokeConfig) (*gateway
 	}, nil
 }
 
-func populateProcessConfigFromResult(req *gateway.StartRequest, res *gateway.Result, cfg *InvokeConfig) error {
-	imgData := res.Metadata[exptypes.ExporterImageConfigKey]
+func populateProcessConfigFromResult(req *gateway.StartRequest, meta map[string][]byte, cfg *InvokeConfig) error {
+	imgData := meta[exptypes.ExporterImageConfigKey]
 	var img *ocispecs.Image
 	if len(imgData) > 0 {
 		img = &ocispecs.Image{}

commands/build.go

@@ -20,7 +20,6 @@ import (
 	"github.com/containerd/console"
 	"github.com/docker/buildx/build"
 	"github.com/docker/buildx/builder"
-	"github.com/docker/buildx/monitor"
 	"github.com/docker/buildx/store"
 	"github.com/docker/buildx/store/storeutil"
 	"github.com/docker/buildx/util/buildflags"
@@ -28,6 +27,7 @@ import (
 	"github.com/docker/buildx/util/confutil"
 	"github.com/docker/buildx/util/desktop"
 	"github.com/docker/buildx/util/dockerutil"
+	"github.com/docker/buildx/util/ioset"
 	"github.com/docker/buildx/util/metricutil"
 	"github.com/docker/buildx/util/osutil"
 	"github.com/docker/buildx/util/platformutil"
@@ -55,7 +55,6 @@ import (
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 	"github.com/spf13/pflag"
-	"github.com/tonistiigi/go-csvvalue"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/metric"
 	"google.golang.org/grpc/codes"
@@ -100,8 +99,6 @@ type buildOptions struct {
 	pull         bool
 	exportPush   bool
 	exportLoad   bool
-
-	invokeConfig *invokeConfig
 }
 
 func (o *buildOptions) toOptions() (*BuildOptions, error) {
@@ -276,7 +273,7 @@ func (o *buildOptionsHash) String() string {
 	return o.result
 }
 
-func runBuild(ctx context.Context, dockerCli command.Cli, options buildOptions) (err error) {
+func runBuild(ctx context.Context, dockerCli command.Cli, debugOpts debuggerOptions, options buildOptions) (err error) {
 	mp := dockerCli.MeterProvider()
 
 	ctx, end, err := tracing.TraceCurrentCommand(ctx, []string{"build", options.contextPath},
@@ -320,10 +317,6 @@ func runBuild(ctx context.Context, dockerCli command.Cli, options buildOptions)
 	}
 	driverType := b.Driver
 
-	var term bool
-	if _, err := console.ConsoleFromFile(os.Stderr); err == nil {
-		term = true
-	}
 	attributes := buildMetricAttributes(dockerCli, driverType, &options)
 
 	ctx2, cancel := context.WithCancelCause(context.TODO())
@@ -332,8 +325,38 @@ func runBuild(ctx context.Context, dockerCli command.Cli, options buildOptions)
 	if err != nil {
 		return err
 	}
+
+	var (
+		out io.Writer = os.Stderr
+		dbg debuggerInstance
+	)
+
+	if debugOpts != nil {
+		if options.dockerfileName == "-" || options.contextPath == "-" {
+			// stdin must be usable for debugger
+			return errors.Errorf("Dockerfile or context from stdin is not supported with debugger")
+		}
+
+		dbg, err = debugOpts.New(ioset.In{
+			Stdin:  io.NopCloser(dockerCli.In()),
+			Stdout: nopCloser{dockerCli.Out()},
+			Stderr: nopCloser{dockerCli.Err()},
+		})
+		if err != nil {
+			return err
+		}
+		out = dbg.Out()
+	}
+
+	var term bool
+	if c, ok := out.(console.File); ok {
+		if _, err := console.ConsoleFromFile(c); err == nil {
+			term = true
+		}
+	}
+
 	var printer *progress.Printer
-	printer, err = progress.NewPrinter(ctx2, os.Stderr, progressMode,
+	printer, err = progress.NewPrinter(ctx2, out, progressMode,
 		progress.WithDesc(
 			fmt.Sprintf("building with %q instance using %s driver", b.Name, b.Driver),
 			fmt.Sprintf("%s:%s", b.Driver, b.Name),
@@ -348,7 +371,7 @@ func runBuild(ctx context.Context, dockerCli command.Cli, options buildOptions)
 	}
 
 	done := timeBuildCommand(mp, attributes)
-	resp, inputs, retErr := runBuildWithOptions(ctx, dockerCli, opts, options, printer)
+	resp, inputs, retErr := runBuildWithOptions(ctx, dockerCli, opts, dbg, printer)
 
 	if err := printer.Wait(); retErr == nil {
 		retErr = err
@@ -406,26 +429,19 @@ func getImageID(resp map[string]string) string {
 	return dgst
 }
 
-func runBuildWithOptions(ctx context.Context, dockerCli command.Cli, opts *BuildOptions, options buildOptions, printer *progress.Printer) (_ *client.SolveResponse, _ *build.Inputs, retErr error) {
-	if options.invokeConfig != nil && (options.dockerfileName == "-" || options.contextPath == "-") {
-		// stdin must be usable for monitor
-		return nil, nil, errors.Errorf("Dockerfile or context from stdin is not supported with invoke")
+func runBuildWithOptions(ctx context.Context, dockerCli command.Cli, opts *BuildOptions, dbg debuggerInstance, printer *progress.Printer) (_ *client.SolveResponse, _ *build.Inputs, retErr error) {
+	var bh build.Handler
+	if dbg != nil {
+		if err := dbg.Start(printer, opts); err != nil {
+			return nil, nil, err
 		}
+		defer dbg.Stop()
 
-	var (
-		in io.ReadCloser
-		m  *monitor.Monitor
-		bh build.Handler
-	)
-	if options.invokeConfig == nil {
-		in = dockerCli.In()
-	} else {
-		m = monitor.New(&options.invokeConfig.InvokeConfig, dockerCli.In(), os.Stdout, os.Stderr, printer)
-		defer m.Close()
-
-		bh = m.Handler()
+		bh = dbg.Handler()
+		dockerCli.SetIn(nil)
 	}
 
+	in := dockerCli.In()
 	for {
 		resp, inputs, err := RunBuild(ctx, dockerCli, opts, in, printer, &bh)
 		if err != nil {
@@ -440,7 +456,7 @@ func runBuildWithOptions(ctx context.Context, dockerCli command.Cli, opts *Build
 	}
 }
 
-func buildCmd(dockerCli command.Cli, rootOpts *rootOptions, debugConfig *debugOptions) *cobra.Command {
+func buildCmd(dockerCli command.Cli, rootOpts *rootOptions, debugger debuggerOptions) *cobra.Command {
 	cFlags := &commonFlags{}
 	options := &buildOptions{}
 
@@ -453,7 +469,9 @@ func buildCmd(dockerCli command.Cli, rootOpts *rootOptions, debugConfig *debugOp
 			"aliases": "docker build, docker builder build, docker image build, docker buildx b",
 		},
 		RunE: func(cmd *cobra.Command, args []string) error {
+			if len(args) > 0 {
 				options.contextPath = args[0]
+			}
 			options.builder = rootOpts.builder
 			options.metadataFile = cFlags.metadataFile
 			options.noCache = false
@@ -467,15 +485,7 @@ func buildCmd(dockerCli command.Cli, rootOpts *rootOptions, debugConfig *debugOp
 			options.progress = cFlags.progress
 			cmd.Flags().VisitAll(checkWarnedFlags)
 
-			if debugConfig != nil && (debugConfig.InvokeFlag != "" || debugConfig.OnFlag != "") {
-				iConfig := new(invokeConfig)
-				if err := iConfig.parseInvokeConfig(debugConfig.InvokeFlag, debugConfig.OnFlag); err != nil {
-					return err
-				}
-				options.invokeConfig = iConfig
-			}
-
-			return runBuild(cmd.Context(), dockerCli, *options)
+			return runBuild(cmd.Context(), dockerCli, debugger, *options)
 		},
 		ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
 			return nil, cobra.ShellCompDirectiveFilterDirs
@@ -866,96 +876,6 @@ func printValue(w io.Writer, printer callFunc, version string, format string, re
 	return printer([]byte(res["result.json"]), w)
 }
 
-type invokeConfig struct {
-	build.InvokeConfig
-	invokeFlag string
-}
-
-func (cfg *invokeConfig) parseInvokeConfig(invoke, on string) error {
-	switch on {
-	case "always":
-		cfg.SuspendOn = build.SuspendAlways
-	case "error":
-		cfg.SuspendOn = build.SuspendError
-	default:
-		if invoke != "" {
-			cfg.SuspendOn = build.SuspendAlways
-		}
-	}
-
-	cfg.invokeFlag = invoke
-	cfg.Tty = true
-	cfg.NoCmd = true
-	switch invoke {
-	case "default", "":
-		return nil
-	case "on-error":
-		// NOTE: we overwrite the command to run because the original one should fail on the failed step.
-		// TODO: make this configurable via flags or restorable from LLB.
-		// Discussion: https://github.com/docker/buildx/pull/1640#discussion_r1113295900
-		cfg.Cmd = []string{"/bin/sh"}
-		cfg.NoCmd = false
-		return nil
-	}
-
-	csvParser := csvvalue.NewParser()
-	csvParser.LazyQuotes = true
-	fields, err := csvParser.Fields(invoke, nil)
-	if err != nil {
-		return err
-	}
-	if len(fields) == 1 && !strings.Contains(fields[0], "=") {
-		cfg.Cmd = []string{fields[0]}
-		cfg.NoCmd = false
-		return nil
-	}
-	cfg.NoUser = true
-	cfg.NoCwd = true
-	for _, field := range fields {
-		parts := strings.SplitN(field, "=", 2)
-		if len(parts) != 2 {
-			return errors.Errorf("invalid value %s", field)
-		}
-		key := strings.ToLower(parts[0])
-		value := parts[1]
-		switch key {
-		case "args":
-			cfg.Cmd = append(cfg.Cmd, maybeJSONArray(value)...)
-			cfg.NoCmd = false
-		case "entrypoint":
-			cfg.Entrypoint = append(cfg.Entrypoint, maybeJSONArray(value)...)
-			if cfg.Cmd == nil {
-				cfg.Cmd = []string{}
-				cfg.NoCmd = false
-			}
-		case "env":
-			cfg.Env = append(cfg.Env, maybeJSONArray(value)...)
-		case "user":
-			cfg.User = value
-			cfg.NoUser = false
-		case "cwd":
-			cfg.Cwd = value
-			cfg.NoCwd = false
-		case "tty":
-			cfg.Tty, err = strconv.ParseBool(value)
-			if err != nil {
-				return errors.Errorf("failed to parse tty: %v", err)
-			}
-		default:
-			return errors.Errorf("unknown key %q", key)
-		}
-	}
-	return nil
-}
-
-func maybeJSONArray(v string) []string {
-	var list []string
-	if err := json.Unmarshal([]byte(v), &list); err == nil {
-		return list
-	}
-	return []string{v}
-}
-
 func callAlias(target *string, value string) cobrautil.BoolFuncValue {
 	return func(s string) error {
 		v, err := strconv.ParseBool(s)
@@ -1210,3 +1130,11 @@ func RunBuild(ctx context.Context, dockerCli command.Cli, in *BuildOptions, inSt
 	}
 	return resp[defaultTargetName], inputs, nil
 }
+
+type nopCloser struct {
+	io.Writer
+}
+
+func (nopCloser) Close() error {
+	return nil
+}

commands/dap.go

@@ -0,0 +1,81 @@
+package commands
+
+import (
+	"context"
+
+	"github.com/docker/buildx/dap"
+	"github.com/docker/buildx/util/cobrautil"
+	"github.com/docker/buildx/util/ioset"
+	"github.com/docker/buildx/util/progress"
+	"github.com/docker/cli/cli/command"
+	"github.com/pkg/errors"
+	"github.com/spf13/cobra"
+)
+
+func dapCmd(dockerCli command.Cli, rootOpts *rootOptions) *cobra.Command {
+	var options dapOptions
+	cmd := &cobra.Command{
+		Use:   "dap",
+		Short: "Start debug adapter protocol compatible debugger",
+	}
+	cobrautil.MarkCommandExperimental(cmd)
+
+	flags := cmd.Flags()
+	flags.StringVar(&options.OnFlag, "on", "error", "When to pause the adapter ([always, error])")
+
+	cobrautil.MarkFlagsExperimental(flags, "on")
+
+	dapBuildCmd := buildCmd(dockerCli, rootOpts, &options)
+	dapBuildCmd.Args = cobra.RangeArgs(0, 1)
+	cmd.AddCommand(dapBuildCmd)
+	return cmd
+}
+
+type dapOptions struct {
+	// OnFlag is a flag to configure the timing of launching the debugger.
+	OnFlag string
+}
+
+func (d *dapOptions) New(in ioset.In) (debuggerInstance, error) {
+	invokeConfig, err := parseInvokeConfig("", d.OnFlag)
+	if err != nil {
+		return nil, err
+	}
+
+	conn := dap.NewConn(in.Stdin, in.Stdout)
+	return &adapterProtocolDebugger{
+		Adapter: dap.New[LaunchConfig](invokeConfig),
+		conn:    conn,
+	}, nil
+}
+
+type LaunchConfig struct {
+	Dockerfile  string `json:"dockerfile,omitempty"`
+	ContextPath string `json:"contextPath,omitempty"`
+	Target      string `json:"target,omitempty"`
+}
+
+type adapterProtocolDebugger struct {
+	*dap.Adapter[LaunchConfig]
+	conn dap.Conn
+}
+
+func (d *adapterProtocolDebugger) Start(printer *progress.Printer, opts *BuildOptions) error {
+	cfg, err := d.Adapter.Start(context.Background(), d.conn)
+	if err != nil {
+		return errors.Wrap(err, "debug adapter did not start")
+	}
+
+	if cfg.Dockerfile != "" {
+		opts.DockerfileName = cfg.Dockerfile
+	}
+	if cfg.ContextPath != "" {
+		opts.ContextPath = cfg.ContextPath
+	}
+	return nil
+}
+
+func (d *adapterProtocolDebugger) Stop() error {
+	defer d.conn.Close()
+	return d.Adapter.Stop()
+}

commands/debug.go

@@ -1,9 +1,21 @@
 package commands
 
 import (
+	"encoding/json"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/docker/buildx/build"
+	"github.com/docker/buildx/monitor"
 	"github.com/docker/buildx/util/cobrautil"
+	"github.com/docker/buildx/util/ioset"
+	"github.com/docker/buildx/util/progress"
 	"github.com/docker/cli/cli/command"
+	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
+	"github.com/tonistiigi/go-csvvalue"
 )
 
 type debugOptions struct {
@@ -14,9 +26,21 @@ type debugOptions struct {
 	OnFlag string
 }
 
+// debuggerOptions will start a debuggerOptions instance.
+type debuggerOptions interface {
+	New(in ioset.In) (debuggerInstance, error)
+}
+
+// debuggerInstance is an instance of a Debugger that has been started.
+type debuggerInstance interface {
+	Start(printer *progress.Printer, opts *BuildOptions) error
+	Handler() build.Handler
+	Stop() error
+	Out() io.Writer
+}
+
 func debugCmd(dockerCli command.Cli, rootOpts *rootOptions) *cobra.Command {
 	var options debugOptions
-
 	cmd := &cobra.Command{
 		Use:   "debug",
 		Short: "Start debugger",
@@ -32,3 +56,123 @@ func debugCmd(dockerCli command.Cli, rootOpts *rootOptions) *cobra.Command {
 	cmd.AddCommand(buildCmd(dockerCli, rootOpts, &options))
 	return cmd
 }
+
+func (d *debugOptions) New(in ioset.In) (debuggerInstance, error) {
+	cfg, err := parseInvokeConfig(d.InvokeFlag, d.OnFlag)
+	if err != nil {
+		return nil, err
+	}
+
+	return &monitorDebuggerInstance{
+		cfg: cfg,
+		in:  in.Stdin,
+	}, nil
+}
+
+type monitorDebuggerInstance struct {
+	cfg *build.InvokeConfig
+	in  io.ReadCloser
+	m   *monitor.Monitor
+}
+
+func (d *monitorDebuggerInstance) Start(printer *progress.Printer, opts *BuildOptions) error {
+	d.m = monitor.New(d.cfg, d.in, os.Stdout, os.Stderr, printer)
+	return nil
+}
+
+func (d *monitorDebuggerInstance) Handler() build.Handler {
+	return d.m.Handler()
+}
+
+func (d *monitorDebuggerInstance) Stop() error {
+	return d.m.Close()
+}
+
+func (d *monitorDebuggerInstance) Out() io.Writer {
+	return os.Stderr
+}
+
+func parseInvokeConfig(invoke, on string) (*build.InvokeConfig, error) {
+	cfg := &build.InvokeConfig{}
+	switch on {
+	case "always":
+		cfg.SuspendOn = build.SuspendAlways
+	case "error":
+		cfg.SuspendOn = build.SuspendError
+	default:
+		if invoke != "" {
+			cfg.SuspendOn = build.SuspendAlways
+		}
+	}
+
+	cfg.Tty = true
+	cfg.NoCmd = true
+	switch invoke {
+	case "default", "":
+		return cfg, nil
+	case "on-error":
+		// NOTE: we overwrite the command to run because the original one should fail on the failed step.
+		// TODO: make this configurable via flags or restorable from LLB.
+		// Discussion: https://github.com/docker/buildx/pull/1640#discussion_r1113295900
+		cfg.Cmd = []string{"/bin/sh"}
+		cfg.NoCmd = false
+		return cfg, nil
+	}
+
+	csvParser := csvvalue.NewParser()
+	csvParser.LazyQuotes = true
+	fields, err := csvParser.Fields(invoke, nil)
+	if err != nil {
+		return nil, err
+	}
+	if len(fields) == 1 && !strings.Contains(fields[0], "=") {
+		cfg.Cmd = []string{fields[0]}
+		cfg.NoCmd = false
+		return cfg, nil
+	}
+	cfg.NoUser = true
+	cfg.NoCwd = true
+	for _, field := range fields {
+		parts := strings.SplitN(field, "=", 2)
+		if len(parts) != 2 {
+			return nil, errors.Errorf("invalid value %s", field)
+		}
+		key := strings.ToLower(parts[0])
+		value := parts[1]
+		switch key {
+		case "args":
+			cfg.Cmd = append(cfg.Cmd, maybeJSONArray(value)...)
+			cfg.NoCmd = false
+		case "entrypoint":
+			cfg.Entrypoint = append(cfg.Entrypoint, maybeJSONArray(value)...)
+			if cfg.Cmd == nil {
+				cfg.Cmd = []string{}
+				cfg.NoCmd = false
+			}
+		case "env":
+			cfg.Env = append(cfg.Env, maybeJSONArray(value)...)
+		case "user":
+			cfg.User = value
+			cfg.NoUser = false
+		case "cwd":
+			cfg.Cwd = value
+			cfg.NoCwd = false
+		case "tty":
+			cfg.Tty, err = strconv.ParseBool(value)
+			if err != nil {
+				return nil, errors.Errorf("failed to parse tty: %v", err)
+			}
+		default:
+			return nil, errors.Errorf("unknown key %q", key)
+		}
+	}
+	return cfg, nil
+}
+
+func maybeJSONArray(v string) []string {
+	var list []string
+	if err := json.Unmarshal([]byte(v), &list); err == nil {
+		return list
+	}
+	return []string{v}
+}

commands/root.go

@@ -120,6 +120,7 @@ func addCommands(cmd *cobra.Command, opts *rootOptions, dockerCli command.Cli) {
 	)
 	if confutil.IsExperimental() {
 		cmd.AddCommand(debugCmd(dockerCli, opts))
+		cmd.AddCommand(dapCmd(dockerCli, opts))
 	}
 
 	cmd.RegisterFlagCompletionFunc( //nolint:errcheck

dap/adapter.go

@@ -0,0 +1,456 @@
+package dap
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"sync"
+
+	"github.com/docker/buildx/build"
+	"github.com/google/go-dap"
+	gateway "github.com/moby/buildkit/frontend/gateway/client"
+	"github.com/pkg/errors"
+	"golang.org/x/sync/errgroup"
+)
+
+type Adapter[T any] struct {
+	srv *Server
+	eg  *errgroup.Group
+	cfg build.InvokeConfig
+
+	initialized   chan struct{}
+	started       chan launchResponse[T]
+	configuration chan struct{}
+
+	evaluateReqCh chan *evaluateRequest
+
+	threads      map[int]*thread
+	threadsMu    sync.RWMutex
+	nextThreadID int
+}
+
+func New[T any](cfg *build.InvokeConfig) *Adapter[T] {
+	d := &Adapter[T]{
+		initialized:   make(chan struct{}),
+		started:       make(chan launchResponse[T], 1),
+		configuration: make(chan struct{}),
+		evaluateReqCh: make(chan *evaluateRequest),
+		threads:       make(map[int]*thread),
+		nextThreadID:  1,
+	}
+	if cfg != nil {
+		d.cfg = *cfg
+	}
+	d.srv = NewServer(d.dapHandler())
+	return d
+}
+
+func (d *Adapter[T]) Start(ctx context.Context, conn Conn) (T, error) {
+	d.eg, _ = errgroup.WithContext(ctx)
+	d.eg.Go(func() error {
+		return d.srv.Serve(ctx, conn)
+	})
+
+	<-d.initialized
+
+	resp, ok := <-d.started
+	if !ok {
+		resp.Error = context.Canceled
+	}
+	return resp.Config, resp.Error
+}
+
+func (d *Adapter[T]) Stop() error {
+	if d.eg == nil {
+		return nil
+	}
+
+	d.srv.Go(func(c Context) {
+		c.C() <- &dap.TerminatedEvent{
+			Event: dap.Event{
+				Event: "terminated",
+			},
+		}
+		// TODO: detect exit code from threads
+		// c.C() <- &dap.ExitedEvent{
+		// 	Event: dap.Event{
+		// 		Event: "exited",
+		// 	},
+		// 	Body: dap.ExitedEventBody{
+		// 		ExitCode: exitCode,
+		// 	},
+		// }
+	})
+	d.srv.Stop()
+
+	err := d.eg.Wait()
+	d.eg = nil
+	return err
+}
+
+func (d *Adapter[T]) Initialize(c Context, req *dap.InitializeRequest, resp *dap.InitializeResponse) error {
+	close(d.initialized)
+
+	// Set capabilities.
+	resp.Body.SupportsConfigurationDoneRequest = true
+	return nil
+}
+
+type launchResponse[T any] struct {
+	Config T
+	Error  error
+}
+
+func (d *Adapter[T]) Launch(c Context, req *dap.LaunchRequest, resp *dap.LaunchResponse) error {
+	defer close(d.started)
+
+	var cfg T
+	if err := json.Unmarshal(req.Arguments, &cfg); err != nil {
+		d.started <- launchResponse[T]{Error: err}
+		return err
+	}
+
+	d.start(c)
+
+	d.started <- launchResponse[T]{Config: cfg}
+	return nil
+}
+
+func (d *Adapter[T]) Disconnect(c Context, req *dap.DisconnectRequest, resp *dap.DisconnectResponse) error {
+	close(d.evaluateReqCh)
+	return nil
+}
+
+func (d *Adapter[T]) start(c Context) {
+	c.Go(d.launch)
+}
+
+func (d *Adapter[T]) Continue(c Context, req *dap.ContinueRequest, resp *dap.ContinueResponse) error {
+	d.threadsMu.RLock()
+	t := d.threads[req.Arguments.ThreadId]
+	d.threadsMu.RUnlock()
+
+	t.Resume(c)
+	return nil
+}
+
+func (d *Adapter[T]) SetBreakpoints(c Context, req *dap.SetBreakpointsRequest, resp *dap.SetBreakpointsResponse) error {
+	// TODO: implement breakpoints
+	for range req.Arguments.Breakpoints {
+		// Fail to create all breakpoints that were requested.
+		resp.Body.Breakpoints = append(resp.Body.Breakpoints, dap.Breakpoint{
+			Verified: false,
+			Message:  "breakpoints unsupported",
+		})
+	}
+	return nil
+}
+
+func (d *Adapter[T]) ConfigurationDone(c Context, req *dap.ConfigurationDoneRequest, resp *dap.ConfigurationDoneResponse) error {
+	d.configuration <- struct{}{}
+	close(d.configuration)
+	return nil
+}
+
+func (d *Adapter[T]) launch(c Context) {
+	// Send initialized event.
+	c.C() <- &dap.InitializedEvent{
+		Event: dap.Event{
+			Event: "initialized",
+		},
+	}
+
+	// Wait for configuration.
+	select {
+	case <-c.Done():
+		return
+	case <-d.configuration:
+		// TODO: actual configuration
+	}
+
+	for {
+		select {
+		case <-c.Done():
+			return
+		case req, ok := <-d.evaluateReqCh:
+			if !ok {
+				return
+			}
+
+			t := d.newThread(c, req.name)
+			started := c.Go(func(c Context) {
+				defer d.deleteThread(c, t)
+				defer close(req.errCh)
+				req.errCh <- t.Evaluate(c, req.c, req.ref, req.meta, d.cfg)
+			})
+
+			if !started {
+				req.errCh <- context.Canceled
+				close(req.errCh)
+			}
+		}
+	}
+}
+
+func (d *Adapter[T]) newThread(ctx Context, name string) (t *thread) {
+	d.threadsMu.Lock()
+	id := d.nextThreadID
+	t = &thread{
+		id:   id,
+		name: name,
+	}
+	d.threads[t.id] = t
+	d.nextThreadID++
+	d.threadsMu.Unlock()
+
+	ctx.C() <- &dap.ThreadEvent{
+		Event: dap.Event{Event: "thread"},
+		Body: dap.ThreadEventBody{
+			Reason:   "started",
+			ThreadId: t.id,
+		},
+	}
+	return t
+}
+
+func (d *Adapter[T]) getThread(id int) (t *thread) {
+	d.threadsMu.Lock()
+	t = d.threads[id]
+	d.threadsMu.Unlock()
+	return t
+}
+
+func (d *Adapter[T]) deleteThread(ctx Context, t *thread) {
+	d.threadsMu.Lock()
+	delete(d.threads, t.id)
+	d.threadsMu.Unlock()
+
+	ctx.C() <- &dap.ThreadEvent{
+		Event: dap.Event{Event: "thread"},
+		Body: dap.ThreadEventBody{
+			Reason:   "exited",
+			ThreadId: t.id,
+		},
+	}
+}
+
+type evaluateRequest struct {
+	name  string
+	c     gateway.Client
+	ref   gateway.Reference
+	meta  map[string][]byte
+	errCh chan<- error
+}
+
+func (d *Adapter[T]) EvaluateResult(ctx context.Context, name string, c gateway.Client, res *gateway.Result) error {
+	eg, _ := errgroup.WithContext(ctx)
+	if res.Ref != nil {
+		eg.Go(func() error {
+			return d.evaluateRef(ctx, name, c, res.Ref, res.Metadata)
+		})
+	}
+
+	for k, ref := range res.Refs {
+		refName := fmt.Sprintf("%s (%s)", name, k)
+		eg.Go(func() error {
+			return d.evaluateRef(ctx, refName, c, ref, res.Metadata)
+		})
+	}
+	return eg.Wait()
+}
+
+func (d *Adapter[T]) evaluateRef(ctx context.Context, name string, c gateway.Client, ref gateway.Reference, meta map[string][]byte) error {
+	errCh := make(chan error, 1)
+
+	// Send a solve request to the launch routine
+	// which will perform the solve in the context of the server.
+	ereq := &evaluateRequest{
+		name:  name,
+		c:     c,
+		ref:   ref,
+		meta:  meta,
+		errCh: errCh,
+	}
+	select {
+	case d.evaluateReqCh <- ereq:
+	case <-ctx.Done():
+		return context.Cause(ctx)
+	}
+
+	// Wait for the response.
+	select {
+	case err := <-errCh:
+		return err
+	case <-ctx.Done():
+		return context.Cause(ctx)
+	}
+}
+
+func (d *Adapter[T]) Threads(c Context, req *dap.ThreadsRequest, resp *dap.ThreadsResponse) error {
+	d.threadsMu.RLock()
+	defer d.threadsMu.RUnlock()
+
+	resp.Body.Threads = []dap.Thread{}
+	for _, t := range d.threads {
+		resp.Body.Threads = append(resp.Body.Threads, dap.Thread{
+			Id:   t.id,
+			Name: t.name,
+		})
+	}
+	return nil
+}
+
+func (d *Adapter[T]) StackTrace(c Context, req *dap.StackTraceRequest, resp *dap.StackTraceResponse) error {
+	t := d.getThread(req.Arguments.ThreadId)
+	if t == nil {
+		return errors.Errorf("no such thread: %d", req.Arguments.ThreadId)
+	}
+
+	resp.Body.StackFrames = t.StackFrames()
+	return nil
+}
+
+func (d *Adapter[T]) evaluate(ctx context.Context, name string, c gateway.Client, res *gateway.Result) error {
+	errCh := make(chan error, 1)
+
+	started := d.srv.Go(func(ctx Context) {
+		defer close(errCh)
+		errCh <- d.EvaluateResult(ctx, name, c, res)
+	})
+	if !started {
+		return context.Canceled
+	}
+
+	select {
+	case err := <-errCh:
+		return err
+	case <-ctx.Done():
+		return context.Cause(ctx)
+	}
+}
+
+func (d *Adapter[T]) Handler() build.Handler {
+	return build.Handler{
+		Evaluate: d.evaluate,
+	}
+}
+
+func (d *Adapter[T]) dapHandler() Handler {
+	return Handler{
+		Initialize:        d.Initialize,
+		Launch:            d.Launch,
+		Continue:          d.Continue,
+		SetBreakpoints:    d.SetBreakpoints,
+		ConfigurationDone: d.ConfigurationDone,
+		Disconnect:        d.Disconnect,
+		Threads:           d.Threads,
+		StackTrace:        d.StackTrace,
+	}
+}
+
+type thread struct {
+	id   int
+	name string
+
+	paused chan struct{}
+	rCtx   *build.ResultHandle
+	mu     sync.Mutex
+}
+
+func (t *thread) Evaluate(ctx Context, c gateway.Client, ref gateway.Reference, meta map[string][]byte, cfg build.InvokeConfig) error {
+	err := ref.Evaluate(ctx)
+	if reason, desc := t.needsDebug(cfg, err); reason != "" {
+		rCtx := build.NewResultHandle(ctx, c, ref, meta, err)
+
+		select {
+		case <-t.pause(ctx, rCtx, reason, desc):
+		case <-ctx.Done():
+			t.Resume(ctx)
+			return context.Cause(ctx)
+		}
+	}
+	return err
+}
+
+func (t *thread) needsDebug(cfg build.InvokeConfig, err error) (reason, desc string) {
+	if !cfg.NeedsDebug(err) {
+		return
+	}
+
+	if err != nil {
+		reason = "exception"
+		desc = "Encountered an error during result evaluation"
+	} else {
+		reason = "pause"
+		desc = "Result evaluation completed"
+	}
+	return
+}
+
+func (t *thread) pause(c Context, rCtx *build.ResultHandle, reason, desc string) <-chan struct{} {
+	if t.paused == nil {
+		t.paused = make(chan struct{})
+	}
+	t.rCtx = rCtx
+
+	c.C() <- &dap.StoppedEvent{
+		Event: dap.Event{Event: "stopped"},
+		Body: dap.StoppedEventBody{
+			Reason:      reason,
+			Description: desc,
+			ThreadId:    t.id,
+		},
+	}
+	return t.paused
+}
+
+func (t *thread) Resume(c Context) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+
+	if t.paused == nil {
+		return
+	}
+
+	if t.rCtx != nil {
+		t.rCtx.Done()
+		t.rCtx = nil
+	}
+
+	close(t.paused)
+	t.paused = nil
+}
+
+// TODO: return a suitable stack frame for the thread.
+// For now, just returns nothing.
+func (t *thread) StackFrames() []dap.StackFrame {
+	return []dap.StackFrame{}
+}
+
+func (d *Adapter[T]) Out() io.Writer {
+	return &adapterWriter[T]{d}
+}
+
+type adapterWriter[T any] struct {
+	*Adapter[T]
+}
+
+func (d *adapterWriter[T]) Write(p []byte) (n int, err error) {
+	started := d.srv.Go(func(c Context) {
+		<-d.initialized
+
+		c.C() <- &dap.OutputEvent{
+			Event: dap.Event{Event: "output"},
+			Body: dap.OutputEventBody{
+				Category: "stdout",
+				Output:   string(p),
+			},
+		}
+	})
+
+	if !started {
+		return 0, io.ErrClosedPipe
+	}
+	return n, nil
+}

dap/adapter_test.go

@@ -0,0 +1,129 @@
+package dap
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"testing"
+	"time"
+
+	"github.com/google/go-dap"
+	"github.com/stretchr/testify/assert"
+	"golang.org/x/sync/errgroup"
+)
+
+func TestLaunch(t *testing.T) {
+	adapter, conn, client := NewTestAdapter[any](t)
+
+	ctx, cancel := context.WithTimeoutCause(context.Background(), 10*time.Second, context.DeadlineExceeded)
+	defer cancel()
+
+	eg, _ := errgroup.WithContext(ctx)
+	eg.Go(func() error {
+		_, err := adapter.Start(ctx, conn)
+		assert.NoError(t, err)
+		return nil
+	})
+
+	var (
+		initialized       = make(chan struct{})
+		configurationDone <-chan *dap.ConfigurationDoneResponse
+	)
+
+	client.RegisterEvent("initialized", func(em dap.EventMessage) {
+		// Send configuration done since we don't do any configuration.
+		configurationDone = DoRequest[*dap.ConfigurationDoneResponse](t, client, &dap.ConfigurationDoneRequest{
+			Request: dap.Request{Command: "configurationDone"},
+		})
+		close(initialized)
+	})
+
+	eg.Go(func() error {
+		initializeResp := <-DoRequest[*dap.InitializeResponse](t, client, &dap.InitializeRequest{
+			Request: dap.Request{Command: "initialize"},
+		})
+		assert.True(t, initializeResp.Success)
+		assert.True(t, initializeResp.Body.SupportsConfigurationDoneRequest)
+
+		launchResp := <-DoRequest[*dap.LaunchResponse](t, client, &dap.LaunchRequest{
+			Request: dap.Request{Command: "launch"},
+		})
+		assert.True(t, launchResp.Success)
+
+		// We should have received the initialized event.
+		select {
+		case <-initialized:
+		default:
+			assert.Fail(t, "did not receive initialized event")
+		}
+
+		select {
+		case <-configurationDone:
+		case <-time.After(time.Second):
+			assert.Fail(t, "did not receive configurationDone response")
+		}
+		return nil
+	})
+
+	eg.Wait()
+}
+
+func NewTestAdapter[T any](t *testing.T) (*Adapter[T], Conn, *Client) {
+	t.Helper()
+
+	rd1, wr1 := io.Pipe()
+	rd2, wr2 := io.Pipe()
+
+	srvConn := logConn(t, "server", NewConn(rd1, wr2))
+	t.Cleanup(func() {
+		srvConn.Close()
+	})
+
+	clientConn := logConn(t, "client", NewConn(rd2, wr1))
+	t.Cleanup(func() {
+		clientConn.Close()
+	})
+
+	adapter := New[T](nil)
+	t.Cleanup(func() { adapter.Stop() })
+
+	client := NewClient(clientConn)
+	return adapter, srvConn, client
+}
+
+func logConn(t *testing.T, prefix string, conn Conn) Conn {
+	return &loggingConn{
+		Conn:   conn,
+		t:      t,
+		prefix: prefix,
+	}
+}
+
+type loggingConn struct {
+	Conn
+	t      *testing.T
+	prefix string
+}
+
+func (c *loggingConn) SendMsg(m dap.Message) error {
+	b, _ := json.Marshal(m)
+	c.t.Logf("[%s] send: %v", c.prefix, string(b))
+
+	err := c.Conn.SendMsg(m)
+	if err != nil {
+		c.t.Logf("[%s] send error: %v", c.prefix, err)
+	}
+	return err
+}
+
+func (c *loggingConn) RecvMsg(ctx context.Context) (dap.Message, error) {
+	m, err := c.Conn.RecvMsg(ctx)
+	if err != nil {
+		c.t.Logf("[%s] recv error: %v", c.prefix, err)
+		return nil, err
+	}
+
+	b, _ := json.Marshal(m)
+	c.t.Logf("[%s] recv: %v", c.prefix, string(b))
+	return m, nil
+}

dap/client_test.go

@@ -0,0 +1,135 @@
+package dap
+
+import (
+	"context"
+	"sync"
+	"sync/atomic"
+	"testing"
+
+	"github.com/google/go-dap"
+	"github.com/pkg/errors"
+	"github.com/stretchr/testify/assert"
+	"golang.org/x/sync/errgroup"
+)
+
+type Client struct {
+	conn Conn
+
+	requests   map[int]chan<- dap.ResponseMessage
+	requestsMu sync.Mutex
+
+	events   map[string]func(dap.EventMessage)
+	eventsMu sync.RWMutex
+
+	seq    atomic.Int64
+	eg     *errgroup.Group
+	cancel context.CancelCauseFunc
+}
+
+func NewClient(conn Conn) *Client {
+	c := &Client{
+		conn:     conn,
+		requests: make(map[int]chan<- dap.ResponseMessage),
+		events:   make(map[string]func(dap.EventMessage)),
+	}
+
+	var ctx context.Context
+	ctx, c.cancel = context.WithCancelCause(context.Background())
+
+	c.eg, _ = errgroup.WithContext(context.Background())
+	c.eg.Go(func() error {
+		for {
+			m, err := conn.RecvMsg(ctx)
+			if err != nil {
+				if errors.Is(err, context.Canceled) {
+					return nil
+				}
+				return err
+			}
+
+			switch m := m.(type) {
+			case dap.RequestMessage:
+				// TODO: no reverse requests are currently supported
+				conn.SendMsg(&dap.Response{
+					ProtocolMessage: dap.ProtocolMessage{
+						Seq:  c.nextSeq(),
+						Type: "response",
+					},
+					RequestSeq: m.GetRequest().GetSeq(),
+					Success:    false,
+					Command:    m.GetRequest().Command,
+					Message:    "not implemented",
+				})
+			case dap.ResponseMessage:
+				c.requestsMu.Lock()
+				req := m.GetResponse().GetResponse().RequestSeq
+				ch := c.requests[req]
+				delete(c.requests, req)
+				c.requestsMu.Unlock()
+
+				if ch != nil {
+					ch <- m
+				}
+			case dap.EventMessage:
+				c.invokeEventCallback(m)
+			}
+		}
+	})
+	return c
+}
+
+func (c *Client) Do(t *testing.T, req dap.RequestMessage) <-chan dap.ResponseMessage {
+	req.GetRequest().Type = "request"
+	req.GetRequest().Seq = c.nextSeq()
+
+	ch := make(chan dap.ResponseMessage, 1)
+	if err := c.conn.SendMsg(req); err != nil {
+		assert.NoError(t, err)
+		close(ch)
+		return ch
+	}
+
+	c.requestsMu.Lock()
+	c.requests[req.GetSeq()] = ch
+	c.requestsMu.Unlock()
+	return ch
+}
+
+func DoRequest[ResponseMessage dap.ResponseMessage, RequestMessage dap.RequestMessage](t *testing.T, c *Client, req RequestMessage) <-chan ResponseMessage {
+	ch := make(chan ResponseMessage, 1)
+	go func() {
+		defer close(ch)
+
+		if m := <-c.Do(t, req); m != nil {
+			ch <- m.(ResponseMessage)
+		}
+	}()
+	return ch
+}
+
+func (c *Client) RegisterEvent(event string, fn func(dap.EventMessage)) {
+	c.eventsMu.Lock()
+	defer c.eventsMu.Unlock()
+
+	c.events[event] = fn
+}
+
+func (c *Client) invokeEventCallback(event dap.EventMessage) {
+	c.eventsMu.RLock()
+	fn := c.events[event.GetEvent().Event]
+	c.eventsMu.RUnlock()
+
+	if fn != nil {
+		fn(event)
+	}
+}
+
+func (c *Client) Close() error {
+	c.cancel(context.Canceled)
+	return c.eg.Wait()
+}
+
+func (c *Client) nextSeq() int {
+	seq := c.seq.Add(1)
+	return int(seq)
+}

dap/conn.go

@@ -0,0 +1,109 @@
+package dap
+
+import (
+	"bufio"
+	"context"
+	"io"
+	"sync"
+
+	"github.com/google/go-dap"
+	"github.com/pkg/errors"
+	"golang.org/x/sync/errgroup"
+)
+
+type Conn interface {
+	SendMsg(m dap.Message) error
+	RecvMsg(ctx context.Context) (dap.Message, error)
+	io.Closer
+}
+
+type conn struct {
+	recvCh <-chan dap.Message
+	sendCh chan<- dap.Message
+
+	ctx    context.Context
+	cancel context.CancelCauseFunc
+
+	eg   *errgroup.Group
+	once sync.Once
+}
+
+func NewConn(rd io.Reader, wr io.Writer) Conn {
+	recvCh := make(chan dap.Message, 100)
+	sendCh := make(chan dap.Message, 100)
+	errCh := make(chan error, 1)
+
+	// Reader input may never close so this is an orphaned goroutine.
+	// It's ok if it does actually close but not necessary for the
+	// proper functioning of this connection.
+	//
+	// The reason this might not close is because stdin close is controlled
+	// by the OS and can't be closed from within the program.
+	go func() {
+		defer close(errCh)
+		defer close(recvCh)
+
+		rd := bufio.NewReader(rd)
+		for {
+			m, err := dap.ReadProtocolMessage(rd)
+			if err != nil {
+				if !errors.Is(err, io.EOF) {
+					// TODO: not actually using this yet
+					errCh <- err
+				}
+				return
+			}
+			recvCh <- m
+		}
+	}()
+
+	eg, _ := errgroup.WithContext(context.Background())
+	eg.Go(func() error {
+		for m := range sendCh {
+			if err := dap.WriteProtocolMessage(wr, m); err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+
+	ctx, cancel := context.WithCancelCause(context.Background())
+	return &conn{
+		recvCh: recvCh,
+		sendCh: sendCh,
+		ctx:    ctx,
+		cancel: cancel,
+		eg:     eg,
+	}
+}
+
+func (c *conn) SendMsg(m dap.Message) error {
+	select {
+	case c.sendCh <- m:
+		return nil
+	default:
+		return errors.New("send channel full")
+	}
+}
+
+func (c *conn) RecvMsg(ctx context.Context) (dap.Message, error) {
+	select {
+	case m, ok := <-c.recvCh:
+		if !ok {
+			return nil, io.EOF
+		}
+		return m, nil
+	case <-ctx.Done():
+		return nil, context.Cause(ctx)
+	case <-c.ctx.Done():
+		return nil, c.ctx.Err()
+	}
+}
+
+func (c *conn) Close() error {
+	c.cancel(context.Canceled)
+	c.once.Do(func() {
+		close(c.sendCh)
+	})
+	return c.eg.Wait()
+}

dap/handler.go

@@ -0,0 +1,58 @@
+package dap
+
+import (
+	"context"
+	"reflect"
+
+	"github.com/google/go-dap"
+	"github.com/pkg/errors"
+)
+
+type Context interface {
+	context.Context
+	C() chan<- dap.Message
+	Go(f func(c Context)) bool
+}
+
+type dispatchContext struct {
+	context.Context
+	srv *Server
+	ch  chan<- dap.Message
+}
+
+func (c *dispatchContext) C() chan<- dap.Message {
+	return c.ch
+}
+
+func (c *dispatchContext) Go(f func(c Context)) bool {
+	return c.srv.Go(f)
+}
+
+type HandlerFunc[Req dap.RequestMessage, Resp dap.ResponseMessage] func(c Context, req Req, resp Resp) error
+
+func (h HandlerFunc[Req, Resp]) Do(c Context, req Req) (resp Resp, err error) {
+	if h == nil {
+		return resp, errors.New("not implemented")
+	}
+
+	respT := reflect.TypeFor[Resp]()
+	rv := reflect.New(respT.Elem())
+	resp = rv.Interface().(Resp)
+	err = h(c, req, resp)
+	return resp, err
+}
+
+type Handler struct {
+	Initialize        HandlerFunc[*dap.InitializeRequest, *dap.InitializeResponse]
+	Launch            HandlerFunc[*dap.LaunchRequest, *dap.LaunchResponse]
+	Attach            HandlerFunc[*dap.AttachRequest, *dap.AttachResponse]
+	SetBreakpoints    HandlerFunc[*dap.SetBreakpointsRequest, *dap.SetBreakpointsResponse]
+	ConfigurationDone HandlerFunc[*dap.ConfigurationDoneRequest, *dap.ConfigurationDoneResponse]
+	Disconnect        HandlerFunc[*dap.DisconnectRequest, *dap.DisconnectResponse]
+	Terminate         HandlerFunc[*dap.TerminateRequest, *dap.TerminateResponse]
+	Continue          HandlerFunc[*dap.ContinueRequest, *dap.ContinueResponse]
+	Restart           HandlerFunc[*dap.RestartRequest, *dap.RestartResponse]
+	Threads           HandlerFunc[*dap.ThreadsRequest, *dap.ThreadsResponse]
+	StackTrace        HandlerFunc[*dap.StackTraceRequest, *dap.StackTraceResponse]
+	Evaluate          HandlerFunc[*dap.EvaluateRequest, *dap.EvaluateResponse]
+}

dap/server.go

@@ -0,0 +1,205 @@
+package dap
+
+import (
+	"context"
+	"sync"
+
+	"github.com/google/go-dap"
+	"github.com/pkg/errors"
+	"golang.org/x/sync/errgroup"
+)
+
+var ErrServerStopped = errors.New("dap: server stopped")
+
+type Server struct {
+	h Handler
+
+	mu sync.RWMutex
+	ch chan dap.Message
+
+	eg     *errgroup.Group
+	ctx    context.Context
+	cancel context.CancelCauseFunc
+
+	initialized bool
+}
+
+func NewServer(h Handler) *Server {
+	return &Server{h: h}
+}
+
+func (s *Server) Serve(ctx context.Context, conn Conn) error {
+	writeCh := make(chan dap.Message)
+	s.ch = writeCh
+
+	s.ctx, s.cancel = context.WithCancelCause(ctx)
+
+	// Start an error group to handle server-initiated tasks.
+	s.eg, _ = errgroup.WithContext(s.ctx)
+	s.eg.Go(func() error {
+		<-s.ctx.Done()
+		return s.ctx.Err()
+	})
+
+	eg, _ := errgroup.WithContext(s.ctx)
+	eg.Go(func() error {
+		return s.readLoop(conn)
+	})
+
+	eg.Go(func() error {
+		return s.writeLoop(conn, writeCh)
+	})
+
+	eg.Go(func() error {
+		// TODO: reevaluate this logic for shutting down
+		defer close(writeCh)
+		err := s.eg.Wait()
+
+		s.mu.Lock()
+		s.ch = nil
+		s.mu.Unlock()
+		return err
+	})
+
+	return eg.Wait()
+}
+
+func (s *Server) readLoop(conn Conn) error {
+	for {
+		m, err := conn.RecvMsg(s.ctx)
+		if err != nil {
+			return nil
+		}
+
+		switch m := m.(type) {
+		case dap.RequestMessage:
+			if ok := s.dispatch(m); !ok {
+				return nil
+			}
+		}
+	}
+}
+
+func (s *Server) dispatch(m dap.RequestMessage) bool {
+	fn := func(c Context) {
+		rmsg, err := s.handleMessage(c, m)
+		if err != nil {
+			rmsg = &dap.Response{}
+			rmsg.GetResponse().Message = err.Error()
+		}
+		rmsg.GetResponse().RequestSeq = m.GetSeq()
+		rmsg.GetResponse().Command = m.GetRequest().Command
+		rmsg.GetResponse().Success = err == nil
+		c.C() <- rmsg
+	}
+	return s.Go(fn)
+}
+
+func (s *Server) handleMessage(c Context, m dap.Message) (dap.ResponseMessage, error) {
+	switch req := m.(type) {
+	case *dap.InitializeRequest:
+		resp, err := s.handleInitialize(c, req)
+		if err != nil {
+			return nil, err
+		}
+		return resp, nil
+	case *dap.LaunchRequest:
+		return s.h.Launch.Do(c, req)
+	case *dap.AttachRequest:
+		return s.h.Attach.Do(c, req)
+	case *dap.SetBreakpointsRequest:
+		return s.h.SetBreakpoints.Do(c, req)
+	case *dap.ConfigurationDoneRequest:
+		return s.h.ConfigurationDone.Do(c, req)
+	case *dap.DisconnectRequest:
+		return s.h.Disconnect.Do(c, req)
+	case *dap.TerminateRequest:
+		return s.h.Terminate.Do(c, req)
+	case *dap.ContinueRequest:
+		return s.h.Continue.Do(c, req)
+	case *dap.RestartRequest:
+		return s.h.Restart.Do(c, req)
+	case *dap.ThreadsRequest:
+		return s.h.Threads.Do(c, req)
+	case *dap.StackTraceRequest:
+		return s.h.StackTrace.Do(c, req)
+	case *dap.EvaluateRequest:
+		return s.h.Evaluate.Do(c, req)
+	default:
+		return nil, errors.New("not implemented")
+	}
+}
+
+func (s *Server) handleInitialize(c Context, req *dap.InitializeRequest) (*dap.InitializeResponse, error) {
+	if s.initialized {
+		return nil, errors.New("already initialized")
+	}
+
+	resp, err := s.h.Initialize.Do(c, req)
+	if err != nil {
+		return nil, err
+	}
+	s.initialized = true
+	return resp, nil
+}
+
+func (s *Server) writeLoop(conn Conn, respCh <-chan dap.Message) error {
+	var seq int
+	for m := range respCh {
+		switch m := m.(type) {
+		case dap.RequestMessage:
+			m.GetRequest().Seq = seq
+			m.GetRequest().Type = "request"
+		case dap.EventMessage:
+			m.GetEvent().Seq = seq
+			m.GetEvent().Type = "event"
+		case dap.ResponseMessage:
+			m.GetResponse().Seq = seq
+			m.GetResponse().Type = "response"
+		}
+		seq++
+
+		if err := conn.SendMsg(m); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (s *Server) Go(fn func(c Context)) bool {
+	acquireChannel := func() (chan<- dap.Message, bool) {
+		s.mu.RLock()
+		defer s.mu.RUnlock()
+
+		return s.ch, s.ch != nil
+	}
+
+	ctx, cancel := context.WithCancelCause(s.ctx)
+	c := &dispatchContext{
+		Context: ctx,
+		srv:     s,
+	}
+
+	started := make(chan bool, 1)
+	s.eg.Go(func() error {
+		var ok bool
+		c.ch, ok = acquireChannel()
+		started <- ok
+
+		if c.ch == nil {
+			return nil
+		}
+
+		defer cancel(context.Canceled)
+		fn(c)
+		return nil
+	})
+	return <-started
+}
+
+func (s *Server) Stop() {
+	s.mu.Lock()
+	s.ch = nil
+	s.mu.Unlock()
+	s.cancel(ErrServerStopped)
+}

docs/reference/buildx.md

@@ -10,10 +10,11 @@ Extended build capabilities with BuildKit
 ### Subcommands
 
 | Name                                 | Description                                                     |
-|:-------------------------------------|:------------------------------------------------|
+|:-------------------------------------|:----------------------------------------------------------------|
 | [`bake`](buildx_bake.md)             | Build from a file                                               |
 | [`build`](buildx_build.md)           | Start a build                                                   |
 | [`create`](buildx_create.md)         | Create a new builder instance                                   |
+| [`dap`](buildx_dap.md)               | Start debug adapter protocol compatible debugger (EXPERIMENTAL) |
 | [`debug`](buildx_debug.md)           | Start debugger (EXPERIMENTAL)                                   |
 | [`dial-stdio`](buildx_dial-stdio.md) | Proxy current stdio streams to builder instance                 |
 | [`du`](buildx_du.md)                 | Disk usage                                                      |

docs/reference/buildx_dap.md

@@ -0,0 +1,23 @@
+# docker buildx dap
+
+<!---MARKER_GEN_START-->
+Start debug adapter protocol compatible debugger (EXPERIMENTAL)
+
+### Subcommands
+
+| Name                           | Description   |
+|:-------------------------------|:--------------|
+| [`build`](buildx_dap_build.md) | Start a build |
+
+
+### Options
+
+| Name            | Type     | Default | Description                                                |
+|:----------------|:---------|:--------|:-----------------------------------------------------------|
+| `--builder`     | `string` |         | Override the configured builder instance                   |
+| `-D`, `--debug` | `bool`   |         | Enable debug logging                                       |
+| `--on`          | `string` | `error` | When to pause the adapter ([always, error]) (EXPERIMENTAL) |
+
+
+<!---MARKER_GEN_END-->
+

docs/reference/buildx_dap_build.md

@@ -0,0 +1,52 @@
+# docker buildx dap build
+
+<!---MARKER_GEN_START-->
+Start a build
+
+### Aliases
+
+`docker build`, `docker builder build`, `docker image build`, `docker buildx b`
+
+### Options
+
+| Name                | Type          | Default   | Description                                                                                                  |
+|:--------------------|:--------------|:----------|:-------------------------------------------------------------------------------------------------------------|
+| `--add-host`        | `stringSlice` |           | Add a custom host-to-IP mapping (format: `host:ip`)                                                          |
+| `--allow`           | `stringArray` |           | Allow extra privileged entitlement (e.g., `network.host`, `security.insecure`)                               |
+| `--annotation`      | `stringArray` |           | Add annotation to the image                                                                                  |
+| `--attest`          | `stringArray` |           | Attestation parameters (format: `type=sbom,generator=image`)                                                 |
+| `--build-arg`       | `stringArray` |           | Set build-time variables                                                                                     |
+| `--build-context`   | `stringArray` |           | Additional build contexts (e.g., name=path)                                                                  |
+| `--builder`         | `string`      |           | Override the configured builder instance                                                                     |
+| `--cache-from`      | `stringArray` |           | External cache sources (e.g., `user/app:cache`, `type=local,src=path/to/dir`)                                |
+| `--cache-to`        | `stringArray` |           | Cache export destinations (e.g., `user/app:cache`, `type=local,dest=path/to/dir`)                            |
+| `--call`            | `string`      | `build`   | Set method for evaluating build (`check`, `outline`, `targets`)                                              |
+| `--cgroup-parent`   | `string`      |           | Set the parent cgroup for the `RUN` instructions during build                                                |
+| `--check`           | `bool`        |           | Shorthand for `--call=check`                                                                                 |
+| `-D`, `--debug`     | `bool`        |           | Enable debug logging                                                                                         |
+| `-f`, `--file`      | `string`      |           | Name of the Dockerfile (default: `PATH/Dockerfile`)                                                          |
+| `--iidfile`         | `string`      |           | Write the image ID to a file                                                                                 |
+| `--label`           | `stringArray` |           | Set metadata for an image                                                                                    |
+| `--load`            | `bool`        |           | Shorthand for `--output=type=docker`                                                                         |
+| `--metadata-file`   | `string`      |           | Write build result metadata to a file                                                                        |
+| `--network`         | `string`      | `default` | Set the networking mode for the `RUN` instructions during build                                              |
+| `--no-cache`        | `bool`        |           | Do not use cache when building the image                                                                     |
+| `--no-cache-filter` | `stringArray` |           | Do not cache specified stages                                                                                |
+| `-o`, `--output`    | `stringArray` |           | Output destination (format: `type=local,dest=path`)                                                          |
+| `--platform`        | `stringArray` |           | Set target platform for build                                                                                |
+| `--progress`        | `string`      | `auto`    | Set type of progress output (`auto`, `quiet`, `plain`, `tty`, `rawjson`). Use plain to show container output |
+| `--provenance`      | `string`      |           | Shorthand for `--attest=type=provenance`                                                                     |
+| `--pull`            | `bool`        |           | Always attempt to pull all referenced images                                                                 |
+| `--push`            | `bool`        |           | Shorthand for `--output=type=registry`                                                                       |
+| `-q`, `--quiet`     | `bool`        |           | Suppress the build output and print image ID on success                                                      |
+| `--sbom`            | `string`      |           | Shorthand for `--attest=type=sbom`                                                                           |
+| `--secret`          | `stringArray` |           | Secret to expose to the build (format: `id=mysecret[,src=/local/secret]`)                                    |
+| `--shm-size`        | `bytes`       | `0`       | Shared memory size for build containers                                                                      |
+| `--ssh`             | `stringArray` |           | SSH agent socket or keys to expose to the build (format: `default\|<id>[=<socket>\|<key>[,<key>]]`)          |
+| `-t`, `--tag`       | `stringArray` |           | Name and optionally a tag (format: `name:tag`)                                                               |
+| `--target`          | `string`      |           | Set the target build stage to build                                                                          |
+| `--ulimit`          | `ulimit`      |           | Ulimit options                                                                                               |
+
+
+<!---MARKER_GEN_END-->
+

go.mod

@@ -21,6 +21,7 @@ require (
 	github.com/docker/docker v28.3.0+incompatible
 	github.com/docker/go-units v0.5.0
 	github.com/gofrs/flock v0.12.1
+	github.com/google/go-dap v0.12.0
 	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510
 	github.com/google/uuid v1.6.0
 	github.com/hashicorp/go-cty-funcs v0.0.0-20250210171435-dda779884a9f

go.sum

@@ -179,6 +179,8 @@ github.com/google/gnostic-models v0.6.8/go.mod h1:5n7qKqH0f5wFt+aWF8CW6pZLLNOfYu
 github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
+github.com/google/go-dap v0.12.0 h1:rVcjv3SyMIrpaOoTAdFDyHs99CwVOItIJGKLQFQhNeM=
+github.com/google/go-dap v0.12.0/go.mod h1:tNjCASCm5cqePi/RVXXWEVqtnNLV1KTWtYOqu6rZNzc=
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
 github.com/google/gofuzz v1.2.0 h1:xRy4A+RhZaiKjJ1bPfwQ8sedCA+YS2YcCHW6ec7JMi0=
 github.com/google/gofuzz v1.2.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=

monitor/monitor.go

@@ -19,6 +19,7 @@ import (
 	"github.com/docker/buildx/util/ioset"
 	"github.com/docker/buildx/util/progress"
 	"github.com/google/shlex"
+	"github.com/moby/buildkit/exporter/containerimage/exptypes"
 	gateway "github.com/moby/buildkit/frontend/gateway/client"
 	"github.com/moby/buildkit/identity"
 	"github.com/moby/buildkit/solver/errdefs"
@@ -56,7 +57,7 @@ func (m *Monitor) Handler() build.Handler {
 	}
 }
 
-func (m *Monitor) Evaluate(ctx context.Context, c gateway.Client, res *gateway.Result) error {
+func (m *Monitor) Evaluate(ctx context.Context, _ string, c gateway.Client, res *gateway.Result) error {
 	buildErr := res.EachRef(func(ref gateway.Reference) error {
 		return ref.Evaluate(ctx)
 	})
@@ -70,7 +71,17 @@ func (m *Monitor) Evaluate(ctx context.Context, c gateway.Client, res *gateway.R
 			logrus.Warnf("failed to print error information: %v", err)
 		}
 
-		rCtx := build.NewResultHandle(ctx, c, res, buildErr)
+		ps, err := exptypes.ParsePlatforms(res.Metadata)
+		if err != nil {
+			return err
+		}
+
+		ref, ok := res.FindRef(ps.Platforms[0].ID)
+		if !ok {
+			return errors.Errorf("no reference found for %s", ps.Platforms[0].ID)
+		}
+
+		rCtx := build.NewResultHandle(ctx, c, ref, res.Metadata, buildErr)
 		if monitorErr := m.Run(ctx, rCtx); monitorErr != nil {
 			if errors.Is(monitorErr, build.ErrRestart) {
 				return build.ErrRestart

util/progress/printer.go

@@ -2,10 +2,10 @@ package progress
 
 import (
 	"context"
+	"io"
 	"os"
 	"sync"
 
-	"github.com/containerd/console"
 	"github.com/docker/buildx/util/logutil"
 	"github.com/mitchellh/hashstructure/v2"
 	"github.com/moby/buildkit/client"
@@ -25,7 +25,7 @@ const (
 )
 
 type Printer struct {
-	out  console.File
+	out  io.Writer
 	mode progressui.DisplayMode
 	opt  *printerOpts
 
@@ -121,7 +121,7 @@ func (p *Printer) ClearLogSource(v any) {
 	}
 }
 
-func NewPrinter(ctx context.Context, out console.File, mode progressui.DisplayMode, opts ...PrinterOpt) (*Printer, error) {
+func NewPrinter(ctx context.Context, out io.Writer, mode progressui.DisplayMode, opts ...PrinterOpt) (*Printer, error) {
 	opt := &printerOpts{}
 	for _, o := range opts {
 		o(opt)

vendor/github.com/google/go-dap/LICENSE

@@ -0,0 +1,202 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
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+      "You" (or "Your") shall mean an individual or Legal Entity
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+      including but not limited to software source code, documentation
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+
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+      form, that is based on (or derived from) the Work and for which the
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+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
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+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
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+
+   7. Disclaimer of Warranty. Unless required by applicable law or
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+
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+
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+   Copyright [yyyy] [name of copyright owner]
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+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
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+   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.

vendor/github.com/google/go-dap/README.md

@@ -0,0 +1,20 @@
+# go-dap: Go implementation of the Debug Adapter Protocol
+
+[![PkgGoDev](https://pkg.go.dev/badge/github.com/google/go-dap)](https://pkg.go.dev/github.com/google/go-dap)
+[![Build Status](https://github.com/google/go-dap/actions/workflows/go.yml/badge.svg?branch=master)](https://github.com/google/go-dap/actions)
+[![Go Report Card](https://goreportcard.com/badge/github.com/google/go-dap)](https://goreportcard.com/report/github.com/google/go-dap)
+
+For an overview of DAP, see
+https://microsoft.github.io/debug-adapter-protocol/overview
+
+## Contributing
+
+We'd love to accept your patches and contributions to this project. See
+[docs/contributing](https://github.com/google/go-dap/blob/master/docs/contributing.md)
+for more details.
+
+## License
+
+This project is licensed under the Apache License 2.0
+
+This is not an officially supported Google product.

vendor/github.com/google/go-dap/codec.go

@@ -0,0 +1,188 @@
+// Copyright 2020 Google LLC
+//
+// 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
+//
+//     https://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.
+
+// This file contains utilities for decoding JSON-encoded bytes into DAP message.
+
+package dap
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// DecodeProtocolMessageFieldError describes which JSON attribute
+// has an unsupported value that the decoding cannot handle.
+type DecodeProtocolMessageFieldError struct {
+	Seq        int
+	SubType    string
+	FieldName  string
+	FieldValue string
+	Message    json.RawMessage
+}
+
+func (e *DecodeProtocolMessageFieldError) Error() string {
+	return fmt.Sprintf("%s %s '%s' is not supported (seq: %d)", e.SubType, e.FieldName, e.FieldValue, e.Seq)
+}
+
+// defaultCodec is used to decode vanilla DAP messages.
+var defaultCodec = NewCodec()
+
+// Codec is responsible for turning byte blobs into DAP messages.
+type Codec struct {
+	eventCtor    map[string]messageCtor
+	requestCtor  map[string]messageCtor
+	responseCtor map[string]messageCtor
+}
+
+// NewCodec constructs a new codec that extends the vanilla DAP protocol.
+// Unless you need to register custom DAP messages, use
+// DecodeProtocolMessage instead.
+func NewCodec() *Codec {
+	ret := &Codec{
+		eventCtor:    make(map[string]messageCtor),
+		requestCtor:  make(map[string]messageCtor),
+		responseCtor: make(map[string]messageCtor),
+	}
+	for k, v := range eventCtor {
+		ret.eventCtor[k] = v
+	}
+	for k, v := range requestCtor {
+		ret.requestCtor[k] = v
+	}
+	for k, v := range responseCtor {
+		ret.responseCtor[k] = v
+	}
+	return ret
+}
+
+// RegisterRequest registers a new custom DAP command, so that it can be
+// unmarshalled by DecodeMessage. Returns an error when the command already
+// exists.
+//
+// The ctor functions need to return a new instance of the underlying DAP
+// message type. A typical usage looks like this:
+//
+//	reqCtor := func() Message { return &LaunchRequest{} }
+//	respCtor := func() Message { return &LaunchResponse{} }
+//      codec.RegisterRequest("launch", reqCtor, respCtor)
+func (c *Codec) RegisterRequest(command string, requestCtor, responseCtor func() Message) error {
+	_, hasReqCtor := c.requestCtor[command]
+	_, hasRespCtor := c.responseCtor[command]
+	if hasReqCtor || hasRespCtor {
+		return fmt.Errorf("command %q is already registered", command)
+	}
+	c.requestCtor[command] = requestCtor
+	c.responseCtor[command] = responseCtor
+	return nil
+}
+
+// RegisterEvent registers a new custom DAP event, so that it can be
+// unmarshalled by DecodeMessage. Returns an error when the event already
+// exists.
+//
+// The ctor function needs to return a new instance of the underlying DAP
+// message type. A typical usage looks like this:
+//
+//	ctor := func() Message { return &StoppedEvent{} }
+//      codec.RegisterEvent("stopped", ctor)
+func (c *Codec) RegisterEvent(event string, ctor func() Message) error {
+	if _, hasEventCtor := c.eventCtor[event]; hasEventCtor {
+		return fmt.Errorf("event %q is already registered", event)
+	}
+	c.eventCtor[event] = ctor
+	return nil
+}
+
+// DecodeMessage parses the JSON-encoded data and returns the result of
+// the appropriate type within the ProtocolMessage hierarchy. If message type,
+// command, etc cannot be cast, returns DecodeProtocolMessageFieldError.
+// See also godoc for json.Unmarshal, which is used for underlying decoding.
+func (c *Codec) DecodeMessage(data []byte) (Message, error) {
+	// This struct is the union of the ResponseMessage, RequestMessage, and
+	// EventMessage types. It is an optimization that saves an additional
+	// json.Unmarshal call.
+	var m struct {
+		ProtocolMessage
+		Command string `json:"command"`
+		Event   string `json:"event"`
+		Success bool   `json:"success"`
+	}
+	if err := json.Unmarshal(data, &m); err != nil {
+		return nil, err
+	}
+	switch m.Type {
+	case "request":
+		return c.decodeRequest(m.Command, m.Seq, data)
+	case "response":
+		return c.decodeResponse(m.Command, m.Seq, m.Success, data)
+	case "event":
+		return c.decodeEvent(m.Event, m.Seq, data)
+	default:
+		return nil, &DecodeProtocolMessageFieldError{m.Seq, "ProtocolMessage", "type", m.Type, json.RawMessage(data)}
+	}
+}
+
+// decodeRequest determines what request type in the ProtocolMessage hierarchy
+// data corresponds to and uses json.Unmarshal to populate the corresponding
+// struct to be returned.
+func (c *Codec) decodeRequest(command string, seq int, data []byte) (Message, error) {
+	ctor, ok := c.requestCtor[command]
+	if !ok {
+		return nil, &DecodeProtocolMessageFieldError{seq, "Request", "command", command, json.RawMessage(data)}
+	}
+	requestPtr := ctor()
+	err := json.Unmarshal(data, requestPtr)
+	return requestPtr, err
+}
+
+// decodeResponse determines what response type in the ProtocolMessage hierarchy
+// data corresponds to and uses json.Unmarshal to populate the corresponding
+// struct to be returned.
+func (c *Codec) decodeResponse(command string, seq int, success bool, data []byte) (Message, error) {
+	if !success {
+		var er ErrorResponse
+		err := json.Unmarshal(data, &er)
+		return &er, err
+	}
+	ctor, ok := c.responseCtor[command]
+	if !ok {
+		return nil, &DecodeProtocolMessageFieldError{seq, "Response", "command", command, json.RawMessage(data)}
+	}
+	responsePtr := ctor()
+	err := json.Unmarshal(data, responsePtr)
+	return responsePtr, err
+}
+
+// decodeEvent determines what event type in the ProtocolMessage hierarchy
+// data corresponds to and uses json.Unmarshal to populate the corresponding
+// struct to be returned.
+func (c *Codec) decodeEvent(event string, seq int, data []byte) (Message, error) {
+	ctor, ok := c.eventCtor[event]
+	if !ok {
+		return nil, &DecodeProtocolMessageFieldError{seq, "Event", "event", event, json.RawMessage(data)}
+	}
+	eventPtr := ctor()
+	err := json.Unmarshal(data, eventPtr)
+	return eventPtr, err
+}
+
+// DecodeProtocolMessage parses the JSON-encoded ProtocolMessage and returns
+// the message embedded in it. If message type, command, etc cannot be cast,
+// returns DecodeProtocolMessageFieldError. See also godoc for json.Unmarshal,
+// which is used for underlying decoding.
+func DecodeProtocolMessage(data []byte) (Message, error) {
+	return defaultCodec.DecodeMessage(data)
+}
+
+type messageCtor func() Message

vendor/github.com/google/go-dap/doc.go

@@ -0,0 +1,20 @@
+// Copyright 2021 Google LLC
+//
+// 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
+//
+//     https://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 dap contains data types and code for Debug Adapter Protocol (DAP) specification.
+// https://github.com/microsoft/vscode-debugadapter-node/blob/main/debugProtocol.json
+package dap
+
+//go:generate go run ./cmd/gentypes/gentypes.go -o schematypes.go -u cmd/gentypes/debugProtocol.json
+

vendor/github.com/google/go-dap/io.go

@@ -0,0 +1,137 @@
+// Copyright 2020 Google LLC
+//
+// 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
+//
+//     https://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.
+
+// This file contains utilities for DAP Base protocol I/O.
+// For additional information, see "Base protocol" section in
+// https://microsoft.github.io/debug-adapter-protocol/overview.
+
+package dap
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"io"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// BaseProtocolError represents base protocol error, which occurs when the raw
+// message does not conform to the header+content format of the base protocol.
+type BaseProtocolError struct {
+	Err string
+}
+
+func (bpe *BaseProtocolError) Error() string { return bpe.Err }
+
+var (
+	// ErrHeaderDelimiterNotCrLfCrLf is returned when only partial header
+	// delimiter \r\n\r\n is encountered.
+	ErrHeaderDelimiterNotCrLfCrLf = &BaseProtocolError{fmt.Sprintf("header delimiter is not %q", crLfcrLf)}
+
+	// ErrHeaderNotContentLength is returned when the parsed header is
+	// not of valid Content-Length format.
+	ErrHeaderNotContentLength = &BaseProtocolError{fmt.Sprintf("header format is not %q", contentLengthHeaderRegex)}
+
+	// ErrHeaderContentTooLong is returned when the content length specified in
+	// the header is above contentMaxLength.
+	ErrHeaderContentTooLong = &BaseProtocolError{fmt.Sprintf("content length over %v bytes", contentMaxLength)}
+)
+
+const (
+	crLfcrLf               = "\r\n\r\n"
+	contentLengthHeaderFmt = "Content-Length: %d\r\n\r\n"
+	contentMaxLength       = 4 * 1024 * 1024
+)
+
+var (
+	contentLengthHeaderRegex = regexp.MustCompile("^Content-Length: ([0-9]+)$")
+)
+
+// WriteBaseMessage formats content with Content-Length header and delimiters
+// as per the base protocol and writes the resulting message to w.
+func WriteBaseMessage(w io.Writer, content []byte) error {
+	header := fmt.Sprintf(contentLengthHeaderFmt, len(content))
+	if _, err := w.Write([]byte(header)); err != nil {
+		return err
+	}
+	_, err := w.Write(content)
+	return err
+}
+
+// ReadBaseMessage reads one message from r consisting of a Content-Length
+// header and a content part. It parses the header to determine the size of
+// the content part and extracts and returns the actual content of the message.
+// Returns nil bytes on error, which can be one of the standard IO errors or
+// a BaseProtocolError defined in this package.
+func ReadBaseMessage(r *bufio.Reader) ([]byte, error) {
+	contentLength, err := readContentLengthHeader(r)
+	if err != nil {
+		return nil, err
+	}
+	if contentLength > contentMaxLength {
+		return nil, ErrHeaderContentTooLong
+	}
+	content := make([]byte, contentLength)
+	if _, err = io.ReadFull(r, content); err != nil {
+		return nil, err
+	}
+	return content, nil
+}
+
+// readContentLengthHeader looks for the only header field that is supported
+// and required:
+// 		Content-Length: [0-9]+\r\n\r\n
+// Extracts and returns the content length.
+func readContentLengthHeader(r *bufio.Reader) (contentLength int64, err error) {
+	// Look for <some header>\r\n\r\n
+	headerWithCr, err := r.ReadString('\r')
+	if err != nil {
+		return 0, err
+	}
+	nextThree := make([]byte, 3)
+	if _, err = io.ReadFull(r, nextThree); err != nil {
+		return 0, err
+	}
+	if string(nextThree) != "\n\r\n" {
+		return 0, ErrHeaderDelimiterNotCrLfCrLf
+	}
+
+	// If header is in the right format, get the length
+	header := strings.TrimSuffix(headerWithCr, "\r")
+	headerAndLength := contentLengthHeaderRegex.FindStringSubmatch(header)
+	if len(headerAndLength) < 2 {
+		return 0, ErrHeaderNotContentLength
+	}
+	return strconv.ParseInt(headerAndLength[1], 10, 64)
+}
+
+// WriteProtocolMessage encodes message and writes it to w.
+func WriteProtocolMessage(w io.Writer, message Message) error {
+	b, err := json.Marshal(message)
+	if err != nil {
+		return err
+	}
+	return WriteBaseMessage(w, b)
+}
+
+// ReadProtocolMessage reads a message from r, decodes and returns it.
+func ReadProtocolMessage(r *bufio.Reader) (Message, error) {
+	content, err := ReadBaseMessage(r)
+	if err != nil {
+		return nil, err
+	}
+	return DecodeProtocolMessage(content)
+}

vendor/modules.txt

@@ -361,6 +361,9 @@ github.com/google/go-cmp/cmp/internal/diff
 github.com/google/go-cmp/cmp/internal/flags
 github.com/google/go-cmp/cmp/internal/function
 github.com/google/go-cmp/cmp/internal/value
+# github.com/google/go-dap v0.12.0
+## explicit; go 1.18
+github.com/google/go-dap
 # github.com/google/gofuzz v1.2.0
 ## explicit; go 1.12
 github.com/google/gofuzz