feat(ps): add ENGINE column gated on label presence

Show an ENGINE column in `compose ps` default table output when the
com.docker.compose.engine label is present. Expose {{.Engine}} for custom
--format templates.

Rename api.EngineLabel to api.ContainerEngineLabel to avoid the
name collision with desktop.EngineLabel (com.docker.desktop.address).

Signed-off-by: Nick Sieger <nick@nicksieger.com>

Author: nicksieger

cmd/compose/ps.go

@@ -156,9 +156,13 @@ func runPs(ctx context.Context, dockerCli command.Cli, backendOptions *BackendOp
 		opts.Format = dockerCli.ConfigFile().PsFormat
 	}
 
+	showEngine := slices.ContainsFunc(containers, func(c api.ContainerSummary) bool {
+		return c.Labels[api.ContainerEngineLabel] != ""
+	})
+
 	containerCtx := cliformatter.Context{
 		Output: dockerCli.Out(),
-		Format: formatter.NewContainerFormat(opts.Format, opts.Quiet, false),
+		Format: formatter.NewContainerFormat(opts.Format, opts.Quiet, false, showEngine),
 		Trunc:  !opts.noTrunc,
 	}
 	return formatter.ContainerWrite(containerCtx, containers)

cmd/formatter/container.go

@@ -42,16 +42,20 @@ const (
 	mountsHeader     = "MOUNTS"
 	localVolumes     = "LOCAL VOLUMES"
 	networksHeader   = "NETWORKS"
+	engineHeader     = "ENGINE"
 )
 
 // NewContainerFormat returns a Format for rendering using a Context
-func NewContainerFormat(source string, quiet bool, size bool) formatter.Format {
+func NewContainerFormat(source string, quiet bool, size bool, engine bool) formatter.Format {
 	switch source {
 	case formatter.TableFormatKey, "": // table formatting is the default if none is set.
 		if quiet {
 			return formatter.DefaultQuietFormat
 		}
 		format := defaultContainerTableFormat
+		if engine {
+			format += `\t{{.Engine}}`
+		}
 		if size {
 			format += `\t{{.Size}}`
 		}
@@ -126,6 +130,7 @@ func NewContainerContext() *ContainerContext {
 		"Status":     formatter.StatusHeader,
 		"Size":       formatter.SizeHeader,
 		"Labels":     formatter.LabelsHeader,
+		"Engine":     engineHeader,
 	}
 	return &containerCtx
 }
@@ -245,6 +250,15 @@ func (c *ContainerContext) Labels() string {
 	return strings.Join(joinLabels, ",")
 }
 
+// Engine returns the name of the engine that runs the container, as stored in
+// the com.docker.compose.engine label, or an empty string if unset.
+func (c *ContainerContext) Engine() string {
+	if c.c.Labels == nil {
+		return ""
+	}
+	return c.c.Labels[api.ContainerEngineLabel]
+}
+
 // Label returns the value of the label with the given name or an empty string
 // if the given label does not exist.
 func (c *ContainerContext) Label(name string) string {

cmd/formatter/container_test.go

@@ -0,0 +1,78 @@
+/*
+   Copyright 2020 Docker Compose CLI authors
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package formatter
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+
+	"github.com/docker/cli/cli/command/formatter"
+	"gotest.tools/v3/assert"
+
+	"github.com/docker/compose/v5/pkg/api"
+)
+
+func TestContainerContextEngine(t *testing.T) {
+	withLabel := ContainerContext{c: api.ContainerSummary{
+		Labels: map[string]string{api.ContainerEngineLabel: "moby"},
+	}}
+	assert.Equal(t, withLabel.Engine(), "moby")
+
+	noLabels := ContainerContext{c: api.ContainerSummary{}}
+	assert.Equal(t, noLabels.Engine(), "")
+
+	otherLabel := ContainerContext{c: api.ContainerSummary{
+		Labels: map[string]string{api.ProjectLabel: "test"},
+	}}
+	assert.Equal(t, otherLabel.Engine(), "")
+}
+
+func TestContainerWriteEngineColumn(t *testing.T) {
+	containers := []api.ContainerSummary{
+		{
+			Name:    "with-engine",
+			Service: "svc1",
+			Labels:  map[string]string{api.ContainerEngineLabel: "moby"},
+		},
+		{
+			Name:    "without-engine",
+			Service: "svc2",
+		},
+	}
+
+	t.Run("engine column shown when label present", func(t *testing.T) {
+		var out bytes.Buffer
+		ctx := formatter.Context{
+			Output: &out,
+			Format: NewContainerFormat("table", false, false, true),
+		}
+		assert.NilError(t, ContainerWrite(ctx, containers))
+		assert.Assert(t, strings.Contains(out.String(), engineHeader), out.String())
+		assert.Assert(t, strings.Contains(out.String(), "moby"), out.String())
+	})
+
+	t.Run("engine column hidden when not requested", func(t *testing.T) {
+		var out bytes.Buffer
+		ctx := formatter.Context{
+			Output: &out,
+			Format: NewContainerFormat("table", false, false, false),
+		}
+		assert.NilError(t, ContainerWrite(ctx, containers))
+		assert.Assert(t, !strings.Contains(out.String(), engineHeader), out.String())
+	})
+}

pkg/api/labels.go

@@ -60,6 +60,8 @@ const (
 	ImageBuilderLabel = "com.docker.compose.image.builder"
 	// ContainerReplaceLabel is set when container is created to replace another container (recreated)
 	ContainerReplaceLabel = "com.docker.compose.replace"
+	// ContainerEngineLabel stores the name of the engine that runs the container
+	ContainerEngineLabel = "com.docker.compose.engine"
 )
 
 // ComposeVersion is the compose tool version as declared by label VersionLabel