dap: add debug adapter implementation

Adds a simple implementation of the debug adapter that supports the very
basics of a debug adapter.

It supports the launch request, the configuration done request, the
creation of threads, stopping, resuming, and disconnecting from server.

It does not support custom breakpoints, stack traces, or variable
inspection yet. These are planned to be added in the future. It also
does not support sending output through the debug adapter yet.

Signed-off-by: Jonathan A. Sternberg <[email protected]>

Author: jsternberg

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

@@ -16,17 +16,18 @@ 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
 // context as the build occurred, which can allow easy debugging of build
 // 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{}