dap: pass exit code through exited event

Pass the exit code through the exited event back to the client and
ensure that the printed text is printed completely.

Previously, the exited event just had a big todo and the printer would
sometimes fail to send messages to the connected client. This moves the
printer wait to before the debug adapter is closed to ensure that all
messages get sent through the connection to the editor. While there, I
also plumbed in the exit code to exited. It's not necessarily the real
exit code but it will produce a zero on build success and a non-zero
code on build failure so that should be good enough.

Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>

commands/build.go

@@ -398,10 +398,6 @@ func runBuild(ctx context.Context, dockerCli command.Cli, debugOpts debuggerOpti
 	done := timeBuildCommand(mp, attributes)
 	resp, inputs, retErr := runBuildWithOptions(ctx, dockerCli, opts, dbg, printer)
 
-	if err := printer.Wait(); retErr == nil {
-		retErr = err
-	}
-
 	done(retErr)
 	if retErr != nil {
 		return retErr
@@ -462,12 +458,21 @@ func runBuildWithOptions(ctx context.Context, dockerCli command.Cli, opts *Build
 		if err := dbg.Start(printer, opts); err != nil {
 			return nil, nil, err
 		}
-		defer dbg.Stop()
+		defer func() { dbg.Stop(retErr) }()
 
 		bh = dbg.Handler()
 		dockerCli.SetIn(nil)
 	}
 
+	// Ensure messages sent to the printer are flushed before the debugger completes.
+	// This prevents late messages from not being sent because the connection was
+	// terminated before completion of the debugger.
+	defer func() {
+		if err := printer.Wait(); retErr == nil {
+			retErr = err
+		}
+	}()
+
 	in := dockerCli.In()
 	for {
 		resp, inputs, err := RunBuild(ctx, dockerCli, opts, in, printer, &bh)

commands/dap.go

@@ -91,9 +91,9 @@ func (d *adapterProtocolDebugger) Start(printer *progress.Printer, opts *BuildOp
 	return nil
 }
 
-func (d *adapterProtocolDebugger) Stop() error {
+func (d *adapterProtocolDebugger) Stop(retErr error) error {
 	defer d.conn.Close()
-	return d.Adapter.Stop()
+	return d.Adapter.Stop(retErr)
 }
 
 func dapAttachCmd() *cobra.Command {

commands/debug.go

@@ -41,7 +41,7 @@ type debuggerOptions interface {
 type debuggerInstance interface {
 	Start(printer *progress.Printer, opts *BuildOptions) error
 	Handler() build.Handler
-	Stop() error
+	Stop(retErr error) error
 	Out() io.Writer
 }
 
@@ -98,7 +98,7 @@ func (d *monitorDebuggerInstance) Handler() build.Handler {
 	return d.m.Handler()
 }
 
-func (d *monitorDebuggerInstance) Stop() error {
+func (d *monitorDebuggerInstance) Stop(_ error) error {
 	return d.m.Close()
 }
 

dap/adapter.go

@@ -83,7 +83,7 @@ func (d *Adapter[C]) Start(conn Conn) (C, error) {
 	return resp.Config, resp.Error
 }
 
-func (d *Adapter[C]) Stop() error {
+func (d *Adapter[C]) Stop(retErr error) error {
 	if d.eg == nil {
 		return nil
 	}
@@ -94,15 +94,27 @@ func (d *Adapter[C]) Stop() error {
 				Event: "terminated",
 			},
 		}
-		// TODO: detect exit code from threads
+
-		// c.C() <- &dap.ExitedEvent{
+		// Send an exit code based on the returned error.
-		// 	Event: dap.Event{
+		// Any error results in sending an exit code of 1 while
-		// 		Event: "exited",
+		// no error sends zero for success.
-		// 	},
+		//
-		// 	Body: dap.ExitedEventBody{
+		// The exited event is sent after the terminated event.
-		// 		ExitCode: exitCode,
+		// See the specification overview diagram on the bottom of the page
-		// 	},
+		// for a detailed flowchart.
-		// }
+		// https://microsoft.github.io/debug-adapter-protocol/overview
+		exitCode := 0
+		if retErr != nil {
+			exitCode = 1
+		}
+		c.C() <- &dap.ExitedEvent{
+			Event: dap.Event{
+				Event: "exited",
+			},
+			Body: dap.ExitedEventBody{
+				ExitCode: exitCode,
+			},
+		}
 	})
 	d.srv.Stop()
 

dap/adapter_test.go

@@ -253,7 +253,7 @@ func NewTestAdapter[C LaunchConfig](t *testing.T) (*Adapter[C], Conn, *daptest.C
 	client := daptest.NewClient(clientConn)
 	t.Cleanup(func() { client.Close() })
 
-	t.Cleanup(func() { adapter.Stop() })
+	t.Cleanup(func() { adapter.Stop(nil) })
 	return adapter, srvConn, client
 }
 

tests/dap_build.go

@@ -5,6 +5,7 @@ import (
 	"os"
 	"os/exec"
 	"path"
+	"path/filepath"
 	"runtime"
 	"slices"
 	"strings"
@@ -87,6 +88,7 @@ var dapBuildTests = []func(t *testing.T, sb integration.Sandbox){
 	testDapBuildStepOut,
 	testDapBuildVariables,
 	testDapBuildDeferredEval,
+	testDapBuildExitedEvent,
 }
 
 func testDapBuild(t *testing.T, sb integration.Sandbox) {
@@ -914,6 +916,73 @@ func testDapBuildDeferredEval(t *testing.T, sb integration.Sandbox) {
 	require.ErrorAs(t, done(true), &exitErr)
 }
 
+func testDapBuildExitedEvent(t *testing.T, sb integration.Sandbox) {
+	t.Run("success", func(t *testing.T) {
+		dir := createTestProject(t)
+		client, done, err := dapBuildCmd(t, sb)
+		require.NoError(t, err)
+
+		ch := make(chan *dap.ExitedEvent, 1)
+		client.RegisterEvent("exited", func(em dap.EventMessage) {
+			ch <- em.(*dap.ExitedEvent)
+			close(ch)
+		})
+
+		// Project should just build normally.
+		doLaunch(t, client, commands.LaunchConfig{
+			Dockerfile:  path.Join(dir, "Dockerfile"),
+			ContextPath: dir,
+		})
+
+		select {
+		case exited := <-ch:
+			require.Equal(t, 0, exited.Body.ExitCode)
+		case <-time.After(5 * time.Second):
+			require.Fail(t, "timeout reached")
+		}
+
+		require.NoError(t, done(true))
+	})
+
+	t.Run("failure", func(t *testing.T) {
+		dir := createTestProject(t)
+		client, done, err := dapBuildCmd(t, sb)
+		require.NoError(t, err)
+
+		ch := make(chan *dap.ExitedEvent, 1)
+		client.RegisterEvent("exited", func(em dap.EventMessage) {
+			ch <- em.(*dap.ExitedEvent)
+			close(ch)
+		})
+
+		// Delete foo from the test project so this will fail.
+		err = os.Remove(filepath.Join(dir, "foo"))
+		require.NoError(t, err)
+
+		interruptCh := pollInterruptEvents(client)
+		doLaunch(t, client, commands.LaunchConfig{
+			Dockerfile:  path.Join(dir, "Dockerfile"),
+			ContextPath: dir,
+		})
+
+		// We will hit an interrupt because of the failure.
+		stopped := waitForInterrupt[*dap.StoppedEvent](t, interruptCh)
+		require.Equal(t, "exception", stopped.Body.Reason)
+
+		// Continue execution which should trigger the exited event.
+		doNext(t, client, stopped.Body.ThreadId)
+		select {
+		case exited := <-ch:
+			require.NotEqual(t, 0, exited.Body.ExitCode)
+		case <-time.After(time.Second):
+			require.Fail(t, "timeout reached")
+		}
+
+		var exitErr *exec.ExitError
+		require.ErrorAs(t, done(false), &exitErr)
+	})
+}
+
 func doLaunch(t *testing.T, client *daptest.Client, config commands.LaunchConfig, bps ...dap.SourceBreakpoint) {
 	t.Helper()