add services/volumes/hash flag for config command

README.md

@@ -1171,9 +1171,15 @@ Validate and view the Compose file
 
 Usage: `nerdctl compose config`
 
-Unimplemented `docker-compose config` (V1) flags: `--resolve-image-digests`, `--no-interpolate`, `--services`, `--volumes`, `--hash`
+Flags:
+- :whale: `-q, --quiet`: Pull without printing progress information
+- :whale: `--services`: Print the service names, one per line.
+- :whale: `--volumes`: Print the volume names, one per line.
+- :whale: `--hash="*"`: Print the service config hash, one per line.
+
+Unimplemented `docker-compose config` (V1) flags: `--resolve-image-digests`, `--no-interpolate`
 
-Unimplemented `docker compose config` (V2) flags: `--resolve-image-digests`, `--no-interpolate`, `--services`, `--volumes`, `--hash`, `--format`, `--output`, `--profiles`
+Unimplemented `docker compose config` (V2) flags: `--resolve-image-digests`, `--no-interpolate`, `--format`, `--output`, `--profiles`
 
 ### :whale: nerdctl compose kill
 Force stop service containers

cmd/nerdctl/compose_config.go

@@ -19,6 +19,7 @@ package main
 import (
 	"fmt"
 
+	"github.com/containerd/nerdctl/pkg/composer"
 	"github.com/spf13/cobra"
 )
 
@@ -31,6 +32,12 @@ func newComposeConfigCommand() *cobra.Command {
 		SilenceErrors: true,
 	}
 	composeConfigCommand.Flags().BoolP("quiet", "q", false, "Only validate the configuration, don't print anything.")
+	composeConfigCommand.Flags().Bool("services", false, "Print the service names, one per line.")
+	composeConfigCommand.Flags().Bool("volumes", false, "Print the volume names, one per line.")
+	composeConfigCommand.Flags().String("hash", "", "Print the service config hash, one per line.")
+	composeConfigCommand.RegisterFlagCompletionFunc("hash", func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+		return []string{"\"*\""}, cobra.ShellCompDirectiveNoFileComp
+	})
 	return composeConfigCommand
 }
 
@@ -43,6 +50,18 @@ func composeConfigAction(cmd *cobra.Command, args []string) error {
 	if err != nil {
 		return err
 	}
+	services, err := cmd.Flags().GetBool("services")
+	if err != nil {
+		return err
+	}
+	volumes, err := cmd.Flags().GetBool("volumes")
+	if err != nil {
+		return err
+	}
+	hash, err := cmd.Flags().GetString("hash")
+	if err != nil {
+		return err
+	}
 
 	client, ctx, cancel, err := newClient(cmd)
 	if err != nil {
@@ -54,8 +73,13 @@ func composeConfigAction(cmd *cobra.Command, args []string) error {
 	if err != nil {
 		return err
 	}
-	if !quiet {
-		return c.Config(ctx)
+	if quiet {
+		return nil
+	}
+	co := composer.ConfigOptions{
+		Services: services,
+		Volumes:  volumes,
+		Hash:     hash,
 	}
-	return nil
+	return c.Config(ctx, cmd.OutOrStdout(), co)
 }

cmd/nerdctl/compose_config_test.go

@@ -17,9 +17,11 @@
 package main
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/containerd/nerdctl/pkg/testutil"
+	"gotest.tools/v3/assert"
 )
 
 func TestComposeConfig(t *testing.T) {
@@ -36,3 +38,40 @@ services:
 
 	base.ComposeCmd("-f", comp.YAMLFullPath(), "config").AssertOutContains("hello:")
 }
+
+func TestComposeConfigWithPrintService(t *testing.T) {
+	base := testutil.NewBase(t)
+
+	var dockerComposeYAML = `
+services:
+  hello1:
+    image: alpine:3.13
+`
+
+	comp := testutil.NewComposeDir(t, dockerComposeYAML)
+	defer comp.CleanUp()
+
+	base.ComposeCmd("-f", comp.YAMLFullPath(), "config", "--services").AssertOutExactly("hello1\n")
+}
+
+func TestComposeConfigWithPrintServiceHash(t *testing.T) {
+	base := testutil.NewBase(t)
+
+	var dockerComposeYAML = `
+services:
+  hello1:
+    image: alpine:%s
+`
+
+	comp := testutil.NewComposeDir(t, fmt.Sprintf(dockerComposeYAML, "3.13"))
+	defer comp.CleanUp()
+
+	base.ComposeCmd("-f", comp.YAMLFullPath(), "config", "--hash=*").AssertOutContains("hello1")
+	hash := base.ComposeCmd("-f", comp.YAMLFullPath(), "config", "--hash=hello1").Out()
+
+	newComp := testutil.NewComposeDir(t, fmt.Sprintf(dockerComposeYAML, "3.14"))
+	defer newComp.CleanUp()
+
+	newHash := base.ComposeCmd("-f", newComp.YAMLFullPath(), "config", "--hash=hello1").Out()
+	assert.Assert(t, hash != newHash)
+}

pkg/composer/config.go

@@ -18,16 +18,69 @@ package composer
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
+	"io"
+	"strings"
 
+	"github.com/compose-spec/compose-go/types"
+	"github.com/opencontainers/go-digest"
 	"gopkg.in/yaml.v2"
 )
 
-func (c *Composer) Config(ctx context.Context) error {
+type ConfigOptions struct {
+	Services bool
+	Volumes  bool
+	Hash     string
+}
+
+func (c *Composer) Config(ctx context.Context, w io.Writer, co ConfigOptions) error {
+	if co.Services {
+		for _, service := range c.project.Services {
+			fmt.Fprintln(w, service.Name)
+		}
+		return nil
+	}
+	if co.Volumes {
+		for volume := range c.project.Volumes {
+			fmt.Fprintln(w, volume)
+		}
+		return nil
+	}
+	if co.Hash != "" {
+		var services []string
+		if co.Hash != "*" {
+			services = strings.Split(co.Hash, ",")
+		}
+		if err := c.project.WithServices(services, func(svc types.ServiceConfig) error {
+			hash, err := ServiceHash(svc)
+			if err != nil {
+				return err
+			}
+			fmt.Fprintf(w, "%s %s\n", svc.Name, hash)
+			return nil
+		}); err != nil {
+			return err
+		}
+		return nil
+	}
 	projectYAML, err := yaml.Marshal(c.project)
 	if err != nil {
 		return err
 	}
-	fmt.Printf("%s", projectYAML)
+	fmt.Fprintf(w, "%s", projectYAML)
 	return nil
 }
+
+// ServiceHash is from https://github.com/docker/compose/blob/v2.2.2/pkg/compose/hash.go#L28-L38
+func ServiceHash(o types.ServiceConfig) (string, error) {
+	// remove the Build config when generating the service hash
+	o.Build = nil
+	o.PullPolicy = ""
+	o.Scale = 1
+	bytes, err := json.Marshal(o)
+	if err != nil {
+		return "", err
+	}
+	return digest.SHA256.FromBytes(bytes).Encoded(), nil
+}