Write docker output to op writer

action/operation_configs.go

@@ -25,10 +25,13 @@ func (cfgs OperationConfigs) ApplyConfig(op *driver.Operation) error {
 		}
 	}
 
-	// If out wasn't configured, default it
+	// If outputs weren't configured, default them
 	if op.Out == nil {
 		op.Out = os.Stdout
 	}
+	if op.Err == nil {
+		op.Err = os.Stderr
+	}
 
 	return nil
 }

action/operation_configs_test.go

@@ -2,6 +2,7 @@ package action
 
 import (
 	"errors"
+	"io/ioutil"
 	"os"
 	"testing"
 
@@ -18,6 +19,7 @@ func TestOperationConfigs_ApplyConfig(t *testing.T) {
 		err := a.ApplyConfig(op)
 		assert.NoError(t, err, "ApplyConfig should not have returned an error")
 		assert.Equal(t, os.Stdout, op.Out, "write to stdout when output is undefined")
+		assert.Equal(t, os.Stderr, op.Err, "write to stderr when output is undefined")
 	})
 
 	t.Run("all config is persisted", func(t *testing.T) {
@@ -30,15 +32,16 @@ func TestOperationConfigs_ApplyConfig(t *testing.T) {
 				return nil
 			},
 			func(op *driver.Operation) error {
-				op.Out = os.Stdout
+				op.Out = ioutil.Discard
 				return nil
 			},
 		}
 		op := &driver.Operation{}
 		err := a.ApplyConfig(op)
 		require.NoError(t, err, "ApplyConfig should not have returned an error")
 		assert.Contains(t, op.Files, "a", "Changes from the first config function were not persisted")
-		assert.Equal(t, os.Stdout, op.Out, "Changes from the second config function were not persisted")
+		assert.Equal(t, ioutil.Discard, op.Out, "Changes from the second config function were not persisted")
+		assert.Equal(t, os.Stderr, op.Err, "Changes from the second config function were not persisted")
 	})
 
 	t.Run("error is returned immediately", func(t *testing.T) {
@@ -47,7 +50,7 @@ func TestOperationConfigs_ApplyConfig(t *testing.T) {
 				return errors.New("oops")
 			},
 			func(op *driver.Operation) error {
-				op.Out = os.Stdout
+				op.Out = ioutil.Discard
 				return nil
 			},
 		}

driver/command/command.go

@@ -109,7 +109,7 @@ func (d *Driver) exec(op *driver.Operation) (driver.OperationResult, error) {
 
 		// Errors not handled here as they only prevent output from the driver being shown, errors in the command execution are handled when command is executed
 
-		io.Copy(op.Out, stderr)
+		io.Copy(op.Err, stderr)
 	}()
 
 	if err = cmd.Start(); err != nil {

driver/docker/docker.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
-	"os"
 	unix_path "path"
 
 	"github.com/docker/cli/cli/command"
@@ -251,8 +250,8 @@ func (d *Driver) exec(op *driver.Operation) (driver.OperationResult, error) {
 		return driver.OperationResult{}, fmt.Errorf("unable to retrieve logs: %v", err)
 	}
 	var (
-		stdout io.Writer = os.Stdout
-		stderr io.Writer = os.Stderr
+		stdout = op.Out
+		stderr = op.Err
 	)
 	if d.containerOut != nil {
 		stdout = d.containerOut

driver/docker/docker_integration_test.go

@@ -70,6 +70,7 @@ func TestDriver_Run(t *testing.T) {
 
 	docker := &Driver{}
 	docker.SetContainerOut(op.Out) // Docker driver writes container stdout to driver.containerOut.
+	docker.SetContainerOut(op.Err)
 	opResult, err := docker.Run(op)
 
 	assert.NoError(t, err)
@@ -81,6 +82,38 @@ func TestDriver_Run(t *testing.T) {
 	}, opResult.Outputs)
 }
 
+func TestDriver_Run_CaptureOutput(t *testing.T) {
+	image := bundle.InvocationImage{
+		BaseImage: bundle.BaseImage{
+			Image:  "carolynvs/cnab-bad-invocation-image:v1",
+			Digest: "sha256:0705cbb5fdeec6752a0a0f707b8e1f7ad63070bf64713a4d23b69ca452fe3d37",
+		},
+	}
+
+	op := &driver.Operation{
+		Installation: "example",
+		Action:       "install",
+		Image:        image,
+		Bundle:       &bundle.Bundle{},
+	}
+
+	var stdout bytes.Buffer
+	var stderr bytes.Buffer
+	op.Out = &stdout
+	op.Err = &stderr
+	op.Environment = map[string]string{
+		"CNAB_ACTION":            op.Action,
+		"CNAB_INSTALLATION_NAME": op.Installation,
+	}
+
+	docker := &Driver{}
+	_, err := docker.Run(op)
+
+	assert.NoError(t, err)
+	assert.Equal(t, "installing bundle...\n", stdout.String())
+	assert.Equal(t, "cat: can't open 'missing-file.txt': No such file or directory\n", stderr.String())
+}
+
 func TestDriver_ValidateImageDigestFail(t *testing.T) {
 	imageFromEnv, ok := os.LookupEnv("DOCKER_INTEGRATION_TEST_IMAGE")
 	var image bundle.InvocationImage

driver/driver.go

@@ -37,6 +37,8 @@ type Operation struct {
 	Outputs map[string]string `json:"outputs"`
 	// Output stream for log messages from the driver
 	Out io.Writer `json:"-"`
+	// Output stream for error messages from the driver
+	Err io.Writer `json:"-"`
 	// Bundle represents the bundle information for use by the operation
 	Bundle *bundle.Bundle
 }