fix: do not prepend garbage in the container.Exec response

container.go

@@ -12,6 +12,7 @@ import (
 	"github.com/docker/docker/pkg/archive"
 	"github.com/docker/go-connections/nat"
 
+	tcexec "github.com/testcontainers/testcontainers-go/exec"
 	"github.com/testcontainers/testcontainers-go/wait"
 )
 
@@ -54,7 +55,7 @@ type Container interface {
 	State(context.Context) (*types.ContainerState, error)        // returns container's running state
 	Networks(context.Context) ([]string, error)                  // get container networks
 	NetworkAliases(context.Context) (map[string][]string, error) // get container network aliases for a network
-	Exec(ctx context.Context, cmd []string) (int, io.Reader, error)
+	Exec(ctx context.Context, cmd []string, options ...tcexec.ProcessOption) (int, io.Reader, error)
 	ContainerIP(context.Context) (string, error)    // get container ip
 	ContainerIPs(context.Context) ([]string, error) // get all container IPs
 	CopyToContainer(ctx context.Context, fileContent []byte, containerFilePath string, fileMode int64) error

docker.go

@@ -33,6 +33,7 @@ import (
 	"github.com/moby/term"
 	specs "github.com/opencontainers/image-spec/specs-go/v1"
 
+	tcexec "github.com/testcontainers/testcontainers-go/exec"
 	"github.com/testcontainers/testcontainers-go/wait"
 )
 
@@ -433,7 +434,7 @@ func (c *DockerContainer) NetworkAliases(ctx context.Context) (map[string][]stri
 	return a, nil
 }
 
-func (c *DockerContainer) Exec(ctx context.Context, cmd []string) (int, io.Reader, error) {
+func (c *DockerContainer) Exec(ctx context.Context, cmd []string, options ...tcexec.ProcessOption) (int, io.Reader, error) {
 	cli := c.provider.client
 	response, err := cli.ContainerExecCreate(ctx, c.ID, types.ExecConfig{
 		Cmd:          cmd,
@@ -450,6 +451,14 @@ func (c *DockerContainer) Exec(ctx context.Context, cmd []string) (int, io.Reade
 		return 0, nil, err
 	}
 
+	opt := &tcexec.ProcessOptions{
+		Reader: hijack.Reader,
+	}
+
+	for _, o := range options {
+		o.Apply(opt)
+	}
+
 	var exitCode int
 	for {
 		execResp, err := cli.ContainerExecInspect(ctx, response.ID)
@@ -465,7 +474,7 @@ func (c *DockerContainer) Exec(ctx context.Context, cmd []string) (int, io.Reade
 		time.Sleep(100 * time.Millisecond)
 	}
 
-	return exitCode, hijack.Reader, nil
+	return exitCode, opt.Reader, nil
 }
 
 type FileFromContainer struct {

docker_exec_test.go

@@ -0,0 +1,67 @@
+package testcontainers
+
+import (
+	"context"
+	"io"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	tcexec "github.com/testcontainers/testcontainers-go/exec"
+)
+
+func TestExecWithMultiplexedResponse(t *testing.T) {
+	ctx := context.Background()
+	req := ContainerRequest{
+		Image: nginxAlpineImage,
+	}
+
+	container, err := GenericContainer(ctx, GenericContainerRequest{
+		ProviderType:     providerType,
+		ContainerRequest: req,
+		Started:          true,
+	})
+
+	require.NoError(t, err)
+	terminateContainerOnEnd(t, ctx, container)
+
+	code, reader, err := container.Exec(ctx, []string{"ls", "/usr/share/nginx"}, tcexec.Multiplexed())
+	require.NoError(t, err)
+	require.Zero(t, code)
+	require.NotNil(t, reader)
+
+	b, err := io.ReadAll(reader)
+	require.NoError(t, err)
+	require.NotNil(t, b)
+
+	str := string(b)
+	require.Equal(t, "html\n", str)
+}
+
+func TestExecWithNonMultiplexedResponse(t *testing.T) {
+	ctx := context.Background()
+	req := ContainerRequest{
+		Image: nginxAlpineImage,
+	}
+
+	container, err := GenericContainer(ctx, GenericContainerRequest{
+		ProviderType:     providerType,
+		ContainerRequest: req,
+		Started:          true,
+	})
+
+	require.NoError(t, err)
+	terminateContainerOnEnd(t, ctx, container)
+
+	code, reader, err := container.Exec(ctx, []string{"ls", "/usr/share/nginx"})
+	require.NoError(t, err)
+	require.Zero(t, code)
+	require.NotNil(t, reader)
+
+	b, err := io.ReadAll(reader)
+	require.NoError(t, err)
+	require.NotNil(t, b)
+
+	str := string(b)
+	require.True(t, strings.HasSuffix(str, "html\n"))
+}

exec/processor.go

@@ -0,0 +1,44 @@
+package exec
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/docker/docker/pkg/stdcopy"
+)
+
+// ProcessOptions defines options applicable to the reader processor
+type ProcessOptions struct {
+	Reader io.Reader
+}
+
+// ProcessOption defines a common interface to modify the reader processor
+// These options can be passed to the Exec function in a variadic way to customize the returned Reader instance
+type ProcessOption interface {
+	Apply(opts *ProcessOptions)
+}
+
+type ProcessOptionFunc func(opts *ProcessOptions)
+
+func (fn ProcessOptionFunc) Apply(opts *ProcessOptions) {
+	fn(opts)
+}
+
+func Multiplexed() ProcessOption {
+	return ProcessOptionFunc(func(opts *ProcessOptions) {
+		done := make(chan struct{})
+
+		var outBuff bytes.Buffer
+		var errBuff bytes.Buffer
+		go func() {
+			if _, err := stdcopy.StdCopy(&outBuff, &errBuff, opts.Reader); err != nil {
+				return
+			}
+			close(done)
+		}()
+
+		<-done
+
+		opts.Reader = &outBuff
+	})
+}

wait/exec_test.go

@@ -12,6 +12,7 @@ import (
 	"github.com/docker/go-connections/nat"
 
 	"github.com/testcontainers/testcontainers-go"
+	tcexec "github.com/testcontainers/testcontainers-go/exec"
 	"github.com/testcontainers/testcontainers-go/wait"
 )
 
@@ -62,7 +63,7 @@ func (st mockExecTarget) Logs(_ context.Context) (io.ReadCloser, error) {
 	return nil, errors.New("not implemented")
 }
 
-func (st mockExecTarget) Exec(ctx context.Context, _ []string) (int, io.Reader, error) {
+func (st mockExecTarget) Exec(ctx context.Context, _ []string, options ...tcexec.ProcessOption) (int, io.Reader, error) {
 	time.Sleep(st.waitDuration)
 
 	if err := ctx.Err(); err != nil {

wait/exit_test.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/docker/docker/api/types"
 	"github.com/docker/go-connections/nat"
+	tcexec "github.com/testcontainers/testcontainers-go/exec"
 )
 
 type exitStrategyTarget struct {
@@ -30,7 +31,7 @@ func (st exitStrategyTarget) Logs(ctx context.Context) (io.ReadCloser, error) {
 	return nil, nil
 }
 
-func (st exitStrategyTarget) Exec(ctx context.Context, cmd []string) (int, io.Reader, error) {
+func (st exitStrategyTarget) Exec(ctx context.Context, cmd []string, options ...tcexec.ProcessOption) (int, io.Reader, error) {
 	return 0, nil, nil
 }
 

wait/log_test.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/docker/docker/api/types"
 	"github.com/docker/go-connections/nat"
+	tcexec "github.com/testcontainers/testcontainers-go/exec"
 )
 
 type noopStrategyTarget struct {
@@ -31,7 +32,7 @@ func (st noopStrategyTarget) Logs(ctx context.Context) (io.ReadCloser, error) {
 	return st.ioReaderCloser, nil
 }
 
-func (st noopStrategyTarget) Exec(ctx context.Context, cmd []string) (int, io.Reader, error) {
+func (st noopStrategyTarget) Exec(ctx context.Context, cmd []string, options ...tcexec.ProcessOption) (int, io.Reader, error) {
 	return 0, nil, nil
 }
 func (st noopStrategyTarget) State(ctx context.Context) (*types.ContainerState, error) {

wait/wait.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/docker/docker/api/types"
 	"github.com/docker/go-connections/nat"
+	tcexec "github.com/testcontainers/testcontainers-go/exec"
 )
 
 type Strategy interface {
@@ -18,7 +19,7 @@ type StrategyTarget interface {
 	Ports(ctx context.Context) (nat.PortMap, error)
 	MappedPort(context.Context, nat.Port) (nat.Port, error)
 	Logs(context.Context) (io.ReadCloser, error)
-	Exec(ctx context.Context, cmd []string) (int, io.Reader, error)
+	Exec(ctx context.Context, cmd []string, options ...tcexec.ProcessOption) (int, io.Reader, error)
 	State(context.Context) (*types.ContainerState, error)
 }