Defer API version negotiation

cli/command/cli.go

@@ -8,6 +8,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"strconv"
+	"sync"
 
 	"github.com/docker/cli/cli/config"
 	cliconfig "github.com/docker/cli/cli/config"
@@ -71,19 +72,20 @@ type Cli interface {
 // DockerCli is an instance the docker command line client.
 // Instances of the client can be returned from NewDockerCli.
 type DockerCli struct {
-	configFile            *configfile.ConfigFile
-	in                    *streams.In
-	out                   *streams.Out
-	err                   io.Writer
-	client                client.APIClient
-	serverInfo            ServerInfo
-	clientInfo            ClientInfo
-	contentTrust          bool
-	newContainerizeClient func(string) (clitypes.ContainerizedClient, error)
-	contextStore          store.Store
-	currentContext        string
-	dockerEndpoint        docker.Endpoint
-	contextStoreConfig    store.Config
+	configFile               *configfile.ConfigFile
+	in                       *streams.In
+	out                      *streams.Out
+	err                      io.Writer
+	client                   client.APIClient
+	serverInfo               ServerInfo
+	clientInfo               ClientInfo
+	contentTrust             bool
+	newContainerizeClient    func(string) (clitypes.ContainerizedClient, error)
+	contextStore             store.Store
+	currentContext           string
+	dockerEndpoint           docker.Endpoint
+	contextStoreConfig       store.Config
+	initializeFromClientOnce sync.Once
 }
 
 // DefaultVersion returns api.defaultVersion or DOCKER_API_VERSION if specified.
@@ -93,6 +95,7 @@ func (cli *DockerCli) DefaultVersion() string {
 
 // Client returns the APIClient
 func (cli *DockerCli) Client() client.APIClient {
+	cli.initializeFromClientOnce.Do(cli.initializeFromClient)
 	return cli.client
 }
 
@@ -133,6 +136,7 @@ func (cli *DockerCli) ConfigFile() *configfile.ConfigFile {
 // ServerInfo returns the server version details for the host this client is
 // connected to
 func (cli *DockerCli) ServerInfo() ServerInfo {
+	cli.initializeFromClientOnce.Do(cli.initializeFromClient)
 	return cli.serverInfo
 }
 
@@ -253,7 +257,6 @@ func (cli *DockerCli) Initialize(opts *cliflags.ClientOptions, ops ...Initialize
 		DefaultVersion:  cli.client.ClientVersion(),
 		HasExperimental: hasExperimental,
 	}
-	cli.initializeFromClient()
 	return nil
 }
 

cli/command/commands/lazychecks/lazychecks.go

@@ -0,0 +1,51 @@
+package lazychecks
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/docker/cli/cli/command"
+	"github.com/spf13/pflag"
+)
+
+var lazyChecks []LazyCheck
+
+const lazyCheckAnnotation = "lazy-checks"
+
+// LazyCheck is a callback that is called lazily to know if a command / flag should be enabled
+type LazyCheck func(clientInfo command.ClientInfo, serverInfo command.ServerInfo, clientVersion string) error
+
+// AddLazyFlagCheck adds a LazyCheck on a flag
+func AddLazyFlagCheck(flagset *pflag.FlagSet, name string, check LazyCheck) {
+	index := len(lazyChecks)
+	lazyChecks = append(lazyChecks, check)
+	f := flagset.Lookup(name)
+	if f == nil {
+		return
+	}
+	if f.Annotations == nil {
+		f.Annotations = map[string][]string{}
+	}
+	f.Annotations[lazyCheckAnnotation] = append(f.Annotations[lazyCheckAnnotation], fmt.Sprintf("%d", index))
+}
+
+// EvaluateFlagLazyChacks evaluates the lazy checks associated with a flag depending on client/server info
+func EvaluateFlagLazyChacks(flag *pflag.Flag, clientInfo command.ClientInfo, serverInfo command.ServerInfo, clientVersion string) error {
+	var errs []string
+	for _, indexStr := range flag.Annotations[lazyCheckAnnotation] {
+		index, err := strconv.ParseInt(indexStr, 10, 32)
+		if err != nil {
+			errs = append(errs, err.Error())
+			continue
+		}
+		if err := lazyChecks[int(index)](clientInfo, serverInfo, clientVersion); err != nil {
+			errs = append(errs, err.Error())
+		}
+	}
+	if len(errs) == 0 {
+		return nil
+	}
+	return errors.New(strings.Join(errs, "\n"))
+}

cli/command/context/cmd.go

@@ -13,10 +13,11 @@ import (
 // NewContextCommand returns the context cli subcommand
 func NewContextCommand(dockerCli command.Cli) *cobra.Command {
 	cmd := &cobra.Command{
-		Use:   "context",
-		Short: "Manage contexts",
-		Args:  cli.NoArgs,
-		RunE:  command.ShowHelp(dockerCli.Err()),
+		Use:         "context",
+		Short:       "Manage contexts",
+		Args:        cli.NoArgs,
+		RunE:        command.ShowHelp(dockerCli.Err()),
+		Annotations: map[string]string{"local-only": ""},
 	}
 	cmd.AddCommand(
 		newCreateCommand(dockerCli),

cli/command/image/build.go

@@ -18,12 +18,14 @@ import (
 
 	"github.com/docker/cli/cli"
 	"github.com/docker/cli/cli/command"
+	"github.com/docker/cli/cli/command/commands/lazychecks"
 	"github.com/docker/cli/cli/command/image/build"
 	"github.com/docker/cli/opts"
 	"github.com/docker/distribution/reference"
 	"github.com/docker/docker/api"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/container"
+	"github.com/docker/docker/api/types/versions"
 	"github.com/docker/docker/pkg/archive"
 	"github.com/docker/docker/pkg/idtools"
 	"github.com/docker/docker/pkg/jsonmessage"
@@ -151,13 +153,19 @@ func NewBuildCommand(dockerCli command.Cli) *cobra.Command {
 
 	flags.StringVar(&options.platform, "platform", os.Getenv("DOCKER_DEFAULT_PLATFORM"), "Set platform if server is multi-platform capable")
 	// Platform is not experimental when BuildKit is used
-	buildkitEnabled, err := command.BuildKitEnabled(dockerCli.ServerInfo())
-	if err == nil && buildkitEnabled {
-		flags.SetAnnotation("platform", "version", []string{"1.38"})
-	} else {
-		flags.SetAnnotation("platform", "version", []string{"1.32"})
-		flags.SetAnnotation("platform", "experimental", nil)
-	}
+	lazychecks.AddLazyFlagCheck(flags, "platform", func(ci command.ClientInfo, si command.ServerInfo, clientVersion string) error {
+		buildkitEnabled, err := command.BuildKitEnabled(si)
+		if err == nil && buildkitEnabled {
+			if versions.LessThan(clientVersion, "1.38") {
+				return fmt.Errorf("with buildkit enabled, --platform flag requires API version 1.38 or greater (current is %s)", clientVersion)
+			}
+		} else {
+			if versions.LessThan(clientVersion, "1.32") || !si.HasExperimental {
+				return fmt.Errorf("with buildkit disabled, --platform requires a daemon with API version 1.32 or greater and experimental enabled")
+			}
+		}
+		return nil
+	})
 
 	flags.BoolVar(&options.squash, "squash", false, "Squash newly built layers into a single new layer")
 	flags.SetAnnotation("squash", "experimental", nil)