introduce generate command as alpha command

Signed-off-by: Guillaume Lours <705411+glours@users.noreply.github.com>

cmd/compose/alpha.go

@@ -33,6 +33,7 @@ func alphaCommand(p *ProjectOptions, dockerCli command.Cli, backend api.Service)
 	cmd.AddCommand(
 		vizCommand(p, dockerCli, backend),
 		publishCommand(p, dockerCli, backend),
+		generateCommand(p, backend),
 	)
 	return cmd
 }

cmd/compose/generate.go

@@ -0,0 +1,82 @@
+/*
+   Copyright 2023 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 compose
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/docker/compose/v2/pkg/api"
+	"github.com/spf13/cobra"
+)
+
+type generateOptions struct {
+	*ProjectOptions
+	Format string
+}
+
+func generateCommand(p *ProjectOptions, backend api.Service) *cobra.Command {
+	opts := generateOptions{
+		ProjectOptions: p,
+	}
+
+	cmd := &cobra.Command{
+		Use:   "generate [OPTIONS] [CONTAINERS...]",
+		Short: "EXPERIMENTAL - Generate a Compose file from existing containers",
+		PreRunE: Adapt(func(ctx context.Context, args []string) error {
+			return nil
+		}),
+		RunE: Adapt(func(ctx context.Context, args []string) error {
+			return runGenerate(ctx, backend, opts, args)
+		}),
+	}
+
+	cmd.Flags().StringVar(&opts.ProjectName, "name", "", "Project name to set in the Compose file")
+	cmd.Flags().StringVar(&opts.ProjectDir, "project-dir", "", "Directory to use for the project")
+	cmd.Flags().StringVar(&opts.Format, "format", "yaml", "Format the output. Values: [yaml | json]")
+	return cmd
+}
+
+func runGenerate(ctx context.Context, backend api.Service, opts generateOptions, containers []string) error {
+	_, _ = fmt.Fprintln(os.Stderr, "generate command is EXPERIMENTAL")
+	if len(containers) == 0 {
+		return fmt.Errorf("at least one container must be specified")
+	}
+	project, err := backend.Generate(ctx, api.GenerateOptions{
+		Containers:  containers,
+		ProjectName: opts.ProjectName,
+	})
+	if err != nil {
+		return err
+	}
+	var content []byte
+	switch opts.Format {
+	case "json":
+		content, err = project.MarshalJSON()
+	case "yaml":
+		content, err = project.MarshalYAML()
+	default:
+		return fmt.Errorf("unsupported format %q", opts.Format)
+	}
+	if err != nil {
+		return err
+	}
+	fmt.Println(string(content))
+
+	return nil
+}

docs/reference/compose_alpha_generate.md

@@ -0,0 +1,17 @@
+# docker compose alpha generate
+
+<!---MARKER_GEN_START-->
+EXPERIMENTAL - Generate a Compose file from existing containers
+
+### Options
+
+| Name            | Type     | Default | Description                               |
+|:----------------|:---------|:--------|:------------------------------------------|
+| `--dry-run`     | `bool`   |         | Execute command in dry run mode           |
+| `--format`      | `string` | `yaml`  | Format the output. Values: [yaml \| json] |
+| `--name`        | `string` |         | Project name to set in the Compose file   |
+| `--project-dir` | `string` |         | Directory to use for the project          |
+
+
+<!---MARKER_GEN_END-->
+

docs/reference/docker_compose_alpha.yaml

@@ -4,9 +4,11 @@ long: Experimental commands
 pname: docker compose
 plink: docker_compose.yaml
 cname:
+    - docker compose alpha generate
     - docker compose alpha publish
     - docker compose alpha viz
 clink:
+    - docker_compose_alpha_generate.yaml
     - docker_compose_alpha_publish.yaml
     - docker_compose_alpha_viz.yaml
 inherited_options:

docs/reference/docker_compose_alpha_generate.yaml

@@ -0,0 +1,53 @@
+command: docker compose alpha generate
+short: EXPERIMENTAL - Generate a Compose file from existing containers
+long: EXPERIMENTAL - Generate a Compose file from existing containers
+usage: docker compose alpha generate [OPTIONS] [CONTAINERS...]
+pname: docker compose alpha
+plink: docker_compose_alpha.yaml
+options:
+    - option: format
+      value_type: string
+      default_value: yaml
+      description: 'Format the output. Values: [yaml | json]'
+      deprecated: false
+      hidden: false
+      experimental: false
+      experimentalcli: false
+      kubernetes: false
+      swarm: false
+    - option: name
+      value_type: string
+      description: Project name to set in the Compose file
+      deprecated: false
+      hidden: false
+      experimental: false
+      experimentalcli: false
+      kubernetes: false
+      swarm: false
+    - option: project-dir
+      value_type: string
+      description: Directory to use for the project
+      deprecated: false
+      hidden: false
+      experimental: false
+      experimentalcli: false
+      kubernetes: false
+      swarm: false
+inherited_options:
+    - option: dry-run
+      value_type: bool
+      default_value: "false"
+      description: Execute command in dry run mode
+      deprecated: false
+      hidden: false
+      experimental: false
+      experimentalcli: false
+      kubernetes: false
+      swarm: false
+deprecated: false
+hidden: false
+experimental: false
+experimentalcli: true
+kubernetes: false
+swarm: false
+

pkg/api/api.go

@@ -92,6 +92,8 @@ type Service interface {
 	Scale(ctx context.Context, project *types.Project, options ScaleOptions) error
 	// Export a service container's filesystem as a tar archive
 	Export(ctx context.Context, projectName string, options ExportOptions) error
+	// Generate generates a Compose Project from existing containers
+	Generate(ctx context.Context, options GenerateOptions) (*types.Project, error)
 }
 
 type ScaleOptions struct {
@@ -562,6 +564,13 @@ type ExportOptions struct {
 	Output  string
 }
 
+type GenerateOptions struct {
+	// ProjectName to set in the Compose file
+	ProjectName string
+	// Containers passed in the command line to be used as reference for service definition
+	Containers []string
+}
+
 const (
 	// STARTING indicates that stack is being deployed
 	STARTING string = "Starting"

pkg/compose/compose.go

@@ -176,7 +176,10 @@ func (s *composeService) projectFromName(containers Containers, projectName stri
 	}
 	set := types.Services{}
 	for _, c := range containers {
-		serviceLabel := c.Labels[api.ServiceLabel]
+		serviceLabel, ok := c.Labels[api.ServiceLabel]
+		if !ok {
+			serviceLabel = getCanonicalContainerName(c)
+		}
 		service, ok := set[serviceLabel]
 		if !ok {
 			service = types.ServiceConfig{