Add Solve API for performing a build on a build definition

This commit adds Solve API to the controller. This receives a build definition,
performs that build using ResultHandler held by that session. After Solve
completes, the client can debug the result using other APIs including Invoke.
Note that the ResultHandle provided by Solve overwrites the ResultHandle
previously stored in that session (possibly generated by the past Build or Solve
API call).

Using this API, user can perform build-and-debugging loop on the same session.

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>

build/result.go

@@ -8,6 +8,7 @@ import (
 	"sync"
 
 	controllerapi "github.com/docker/buildx/controller/pb"
+	"github.com/docker/buildx/util/progress"
 	"github.com/moby/buildkit/client"
 	"github.com/moby/buildkit/exporter/containerimage/exptypes"
 	gateway "github.com/moby/buildkit/frontend/gateway/client"
@@ -93,6 +94,8 @@ func NewResultHandle(ctx context.Context, cc *client.Client, opt client.SolveOpt
 			if res != nil && err == nil {
 				if noEval {
 					respHandle = &ResultHandle{
+						client:   cc,
+						solveOpt: opt,
 						done:     make(chan struct{}),
 						gwClient: c,
 						gwCtx:    ctx,
@@ -127,6 +130,8 @@ func NewResultHandle(ctx context.Context, cc *client.Client, opt client.SolveOpt
 				var se *errdefs.SolveError
 				if errors.As(err, &se) {
 					respHandle = &ResultHandle{
+						client:   cc,
+						solveOpt: opt,
 						done:     make(chan struct{}),
 						solveErr: se,
 						gwClient: c,
@@ -183,6 +188,8 @@ func NewResultHandle(ctx context.Context, cc *client.Client, opt client.SolveOpt
 				return nil, errors.Wrap(err, "inconsistent solve result")
 			}
 			respHandle = &ResultHandle{
+				client:   cc,
+				solveOpt: opt,
 				done:     make(chan struct{}),
 				res:      res,
 				gwClient: c,
@@ -265,8 +272,27 @@ func evalDefinition(ctx context.Context, c gateway.Client, defs *result.Result[*
 	return res, nil
 }
 
+func SolveWithResultHandler(ctx context.Context, product string, resultCtx *ResultHandle, target *pb.Definition, pw progress.Writer) (*ResultHandle, error) {
+	opt := resultCtx.solveOpt
+	opt.Ref = ""
+	opt.Exports = nil
+	opt.CacheExports = nil
+	ch, done := progress.NewChannel(pw)
+	defer func() { <-done }()
+	h, _, err := NewResultHandle(ctx, resultCtx.client, opt, product, func(ctx context.Context, c gateway.Client) (*gateway.Result, error) {
+		return c.Solve(ctx, gateway.SolveRequest{
+			Evaluate:   true,
+			Definition: target,
+		})
+	}, ch, false)
+	return h, err
+}
+
 // ResultHandle is a build result with the client that built it.
 type ResultHandle struct {
+	client   *client.Client
+	solveOpt client.SolveOpt
+
 	res      *gateway.Result
 	solveErr *errdefs.SolveError
 
@@ -295,6 +321,10 @@ func (r *ResultHandle) Done() {
 	})
 }
 
+func (r *ResultHandle) SolveError() *errdefs.SolveError {
+	return r.solveErr
+}
+
 func (r *ResultHandle) registerCleanup(f func()) {
 	r.cleanupsMu.Lock()
 	r.cleanups = append(r.cleanups, f)