feat(experiments): add experimental feature state (docker#11633)

Use environment variable for global opt-out and Docker Desktop (if
available) to determine specific experiment states.

In the future, we'll allow per-feature opt-in/opt-out via env vars
as well, but currently there is a single `COMPOSE_EXPERIMENTAL` env
var that can be used to opt-out of all experimental features
independently of Docker Desktop configuration.

Author: milas

cmd/compose/compose.go

@@ -38,6 +38,7 @@ import (
 	"github.com/docker/cli/cli/command"
 	"github.com/docker/compose/v2/cmd/formatter"
 	"github.com/docker/compose/v2/internal/desktop"
+	"github.com/docker/compose/v2/internal/experimental"
 	"github.com/docker/compose/v2/internal/tracing"
 	"github.com/docker/compose/v2/pkg/api"
 	"github.com/docker/compose/v2/pkg/compose"
@@ -66,6 +67,14 @@ const (
 	ComposeEnvFiles = "COMPOSE_ENV_FILES"
 )
 
+type Backend interface {
+	api.Service
+
+	SetDesktopClient(cli *desktop.Client)
+
+	SetExperiments(experiments *experimental.State)
+}
+
 // Command defines a compose CLI command as a func with args
 type Command func(context.Context, []string) error
 
@@ -326,7 +335,7 @@ func RunningAsStandalone() bool {
 }
 
 // RootCommand returns the compose command with its child commands
-func RootCommand(dockerCli command.Cli, backend api.Service) *cobra.Command { //nolint:gocyclo
+func RootCommand(dockerCli command.Cli, backend Backend) *cobra.Command { //nolint:gocyclo
 	// filter out useless commandConn.CloseWrite warning message that can occur
 	// when using a remote context that is unreachable: "commandConn.CloseWrite: commandconn: failed to wait: signal: killed"
 	// https://github.com/docker/cli/blob/e1f24d3c93df6752d3c27c8d61d18260f141310c/cli/connhelper/commandconn/commandconn.go#L203-L215
@@ -337,6 +346,7 @@ func RootCommand(dockerCli command.Cli, backend api.Service) *cobra.Command { //
 		"commandConn.CloseRead:",
 	))
 
+	experiments := experimental.NewState()
 	opts := ProjectOptions{}
 	var (
 		ansi     string
@@ -486,20 +496,32 @@ func RootCommand(dockerCli command.Cli, backend api.Service) *cobra.Command { //
 			cmd.SetContext(ctx)
 
 			// (6) Desktop integration
-			if db, ok := backend.(desktop.IntegrationService); ok {
-				if err := db.MaybeEnableDesktopIntegration(ctx); err != nil {
+			var desktopCli *desktop.Client
+			if !dryRun {
+				if desktopCli, err = desktop.NewFromDockerClient(ctx, dockerCli); desktopCli != nil {
+					logrus.Debugf("Enabled Docker Desktop integration (experimental) @ %s", desktopCli.Endpoint())
+					backend.SetDesktopClient(desktopCli)
+				} else if err != nil {
 					// not fatal, Compose will still work but behave as though
 					// it's not running as part of Docker Desktop
 					logrus.Debugf("failed to enable Docker Desktop integration: %v", err)
+				} else {
+					logrus.Trace("Docker Desktop integration not enabled")
 				}
 			}
 
+			// (7) experimental features
+			if err := experiments.Load(ctx, desktopCli); err != nil {
+				logrus.Debugf("Failed to query feature flags from Desktop: %v", err)
+			}
+			backend.SetExperiments(experiments)
+
 			return nil
 		},
 	}
 
 	c.AddCommand(
-		upCommand(&opts, dockerCli, backend),
+		upCommand(&opts, dockerCli, backend, experiments),
 		downCommand(&opts, dockerCli, backend),
 		startCommand(&opts, dockerCli, backend),
 		restartCommand(&opts, dockerCli, backend),

cmd/compose/up.go

@@ -27,6 +27,7 @@ import (
 	"github.com/compose-spec/compose-go/v2/types"
 	"github.com/docker/cli/cli/command"
 	"github.com/docker/compose/v2/cmd/formatter"
+	"github.com/docker/compose/v2/internal/experimental"
 	xprogress "github.com/moby/buildkit/util/progress/progressui"
 	"github.com/spf13/cobra"
 
@@ -76,7 +77,7 @@ func (opts upOptions) apply(project *types.Project, services []string) (*types.P
 	return project, nil
 }
 
-func upCommand(p *ProjectOptions, dockerCli command.Cli, backend api.Service) *cobra.Command {
+func upCommand(p *ProjectOptions, dockerCli command.Cli, backend api.Service, experiments *experimental.State) *cobra.Command {
 	up := upOptions{}
 	create := createOptions{}
 	build := buildOptions{ProjectOptions: p}
@@ -96,7 +97,7 @@ func upCommand(p *ProjectOptions, dockerCli command.Cli, backend api.Service) *c
 			if len(up.attach) != 0 && up.attachDependencies {
 				return errors.New("cannot combine --attach and --attach-dependencies")
 			}
-			return runUp(ctx, dockerCli, backend, create, up, build, project, services)
+			return runUp(ctx, dockerCli, backend, experiments, create, up, build, project, services)
 		}),
 		ValidArgsFunction: completeServiceNames(dockerCli, p),
 	}
@@ -160,6 +161,7 @@ func runUp(
 	ctx context.Context,
 	dockerCli command.Cli,
 	backend api.Service,
+	_ *experimental.State,
 	createOptions createOptions,
 	upOptions upOptions,
 	buildOptions buildOptions,

cmd/main.go

@@ -36,7 +36,10 @@ import (
 
 func pluginMain() {
 	plugin.Run(func(dockerCli command.Cli) *cobra.Command {
-		backend := compose.NewComposeService(dockerCli)
+		// TODO(milas): this cast is safe but we should not need to do this,
+		// 	we should expose the concrete service type so that we do not need
+		// 	to rely on the `api.Service` interface internally
+		backend := compose.NewComposeService(dockerCli).(commands.Backend)
 		cmd := commands.RootCommand(dockerCli, backend)
 		originalPreRunE := cmd.PersistentPreRunE
 		cmd.PersistentPreRunE = func(cmd *cobra.Command, args []string) error {

internal/desktop/client.go

@@ -30,7 +30,8 @@ import (
 
 // Client for integration with Docker Desktop features.
 type Client struct {
-	client *http.Client
+	apiEndpoint string
+	client      *http.Client
 }
 
 // NewClient creates a Desktop integration client for the provided in-memory
@@ -45,11 +46,16 @@ func NewClient(apiEndpoint string) *Client {
 	transport = otelhttp.NewTransport(transport)
 
 	c := &Client{
-		client: &http.Client{Transport: transport},
+		apiEndpoint: apiEndpoint,
+		client:      &http.Client{Transport: transport},
 	}
 	return c
 }
 
+func (c *Client) Endpoint() string {
+	return c.apiEndpoint
+}
+
 // Close releases any open connections.
 func (c *Client) Close() error {
 	c.client.CloseIdleConnections()
@@ -84,6 +90,35 @@ func (c *Client) Ping(ctx context.Context) (*PingResponse, error) {
 	return &ret, nil
 }
 
+type FeatureFlagResponse map[string]FeatureFlagValue
+
+type FeatureFlagValue struct {
+	Enabled bool `json:"enabled"`
+}
+
+func (c *Client) FeatureFlags(ctx context.Context) (FeatureFlagResponse, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, backendURL("/features"), http.NoBody)
+	if err != nil {
+		return nil, err
+	}
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		_ = resp.Body.Close()
+	}()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("unexpected status code: %d", resp.StatusCode)
+	}
+
+	var ret FeatureFlagResponse
+	if err := json.NewDecoder(resp.Body).Decode(&ret); err != nil {
+		return nil, err
+	}
+	return ret, nil
+}
+
 // backendURL generates a URL for the given API path.
 //
 // NOTE: Custom transport handles communication. The host is to create a valid

internal/desktop/discovery.go

@@ -0,0 +1,62 @@
+/*
+   Copyright 2024 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 desktop
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/docker/cli/cli/command"
+)
+
+// engineLabelDesktopAddress is used to detect that Compose is running with a
+// Docker Desktop context. When this label is present, the value is an endpoint
+// address for an in-memory socket (AF_UNIX or named pipe).
+const engineLabelDesktopAddress = "com.docker.desktop.address"
+
+// NewFromDockerClient creates a Desktop Client using the Docker CLI client to
+// auto-discover the Desktop CLI socket endpoint (if available).
+//
+// An error is returned if there is a failure communicating with Docker Desktop,
+// but even on success, a nil Client can be returned if the active Docker Engine
+// is not a Desktop instance.
+func NewFromDockerClient(ctx context.Context, dockerCli command.Cli) (*Client, error) {
+	// safeguard to make sure this doesn't get stuck indefinitely
+	ctx, cancel := context.WithTimeout(ctx, time.Second)
+	defer cancel()
+
+	info, err := dockerCli.Client().Info(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("querying server info: %w", err)
+	}
+	for _, l := range info.Labels {
+		k, v, ok := strings.Cut(l, "=")
+		if !ok || k != engineLabelDesktopAddress {
+			continue
+		}
+
+		desktopCli := NewClient(v)
+		_, err := desktopCli.Ping(ctx)
+		if err != nil {
+			return nil, fmt.Errorf("pinging Desktop API: %w", err)
+		}
+		return desktopCli, nil
+	}
+	return nil, nil
+}

internal/desktop/integration.go

@@ -0,0 +1,85 @@
+/*
+   Copyright 2024 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 experimental
+
+import (
+	"context"
+	"os"
+	"strconv"
+
+	"github.com/docker/compose/v2/internal/desktop"
+)
+
+// envComposeExperimentalGlobal can be set to a falsy value (e.g. 0, false) to
+// globally opt-out of any experimental features in Compose.
+const envComposeExperimentalGlobal = "COMPOSE_EXPERIMENTAL"
+
+// State of experiments (enabled/disabled) based on environment and local config.
+type State struct {
+	// active is false if experiments have been opted-out of globally.
+	active        bool
+	desktopValues desktop.FeatureFlagResponse
+}
+
+func NewState() *State {
+	// experimental features have individual controls, but users can opt out
+	// of ALL experiments easily if desired
+	experimentsActive := true
+	if v := os.Getenv(envComposeExperimentalGlobal); v != "" {
+		experimentsActive, _ = strconv.ParseBool(v)
+	}
+	return &State{
+		active: experimentsActive,
+	}
+}
+
+func (s *State) Load(ctx context.Context, client *desktop.Client) error {
+	if !s.active {
+		// user opted out of experiments globally, no need to load state from
+		// Desktop
+		return nil
+	}
+
+	if client == nil {
+		// not running under Docker Desktop
+		return nil
+	}
+
+	desktopValues, err := client.FeatureFlags(ctx)
+	if err != nil {
+		return err
+	}
+	s.desktopValues = desktopValues
+	return nil
+}
+
+func (s *State) NavBar() bool {
+	return s.determineFeatureState("ComposeNav")
+}
+
+func (s *State) AutoFileShares() bool {
+	return s.determineFeatureState("ComposeAutoFileShares")
+}
+
+func (s *State) determineFeatureState(name string) bool {
+	if !s.active || s.desktopValues == nil {
+		return false
+	}
+	// TODO(milas): we should add individual environment variable overrides
+	// 	per-experiment in a generic way here
+	return s.desktopValues[name].Enabled
+}

internal/experimental/experimental.go

@@ -19,9 +19,10 @@
 package locker
 
 import (
+	"os"
+
 	"github.com/docker/docker/pkg/pidfile"
 	"github.com/mitchellh/go-ps"
-	"os"
 )
 
 func (f *Pidfile) Lock() error {

internal/locker/pidfile_windows.go

@@ -27,6 +27,7 @@ import (
 	"sync"
 
 	"github.com/docker/compose/v2/internal/desktop"
+	"github.com/docker/compose/v2/internal/experimental"
 	"github.com/docker/docker/api/types/volume"
 	"github.com/jonboulle/clockwork"
 
@@ -62,8 +63,9 @@ func NewComposeService(dockerCli command.Cli) api.Service {
 }
 
 type composeService struct {
-	dockerCli  command.Cli
-	desktopCli *desktop.Client
+	dockerCli   command.Cli
+	desktopCli  *desktop.Client
+	experiments *experimental.State
 
 	clock          clockwork.Clock
 	maxConcurrency int