From e38e6c51ffb55405321038dfcf3a477faeddbf77 Mon Sep 17 00:00:00 2001
From: CrazyMax <crazy-max@users.noreply.github.com>
Date: Thu, 24 Feb 2022 17:57:47 +0100
Subject: [PATCH 1/2] bring back and expose BuildKitEnabled func

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>
---
 cli/command/cli.go   | 22 ++++++++++++++++++++++
 internal/test/cli.go |  5 +++++
 2 files changed, 27 insertions(+)

diff --git a/cli/command/cli.go b/cli/command/cli.go
index c01a66d886e3..1b162a832665 100644
--- a/cli/command/cli.go
+++ b/cli/command/cli.go
@@ -7,6 +7,7 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
+	"strconv"
 	"strings"
 	"time"
 
@@ -58,6 +59,7 @@ type Cli interface {
 	ManifestStore() manifeststore.Store
 	RegistryClient(bool) registryclient.RegistryClient
 	ContentTrustEnabled() bool
+	BuildKitEnabled() (bool, error)
 	ContextStore() store.Store
 	CurrentContext() string
 	DockerEndpoint() docker.Endpoint
@@ -167,6 +169,26 @@ func (cli *DockerCli) ContentTrustEnabled() bool {
 	return cli.contentTrust
 }
 
+// BuildKitEnabled returns buildkit is enabled or not.
+func (cli *DockerCli) BuildKitEnabled() (bool, error) {
+	// use DOCKER_BUILDKIT env var value if set
+	if v, ok := os.LookupEnv("DOCKER_BUILDKIT"); ok {
+		enabled, err := strconv.ParseBool(v)
+		if err != nil {
+			return false, errors.Wrap(err, "DOCKER_BUILDKIT environment variable expects boolean value")
+		}
+		return enabled, nil
+	}
+	// if a builder alias is defined, we are using BuildKit
+	aliasMap := cli.ConfigFile().Aliases
+	if _, ok := aliasMap["builder"]; ok {
+		return true, nil
+	}
+	// otherwise, assume BuildKit is enabled but
+	// not if wcow reported from server side
+	return cli.ServerInfo().OSType != "windows", nil
+}
+
 // ManifestStore returns a store for local manifests
 func (cli *DockerCli) ManifestStore() manifeststore.Store {
 	// TODO: support override default location from config file
diff --git a/internal/test/cli.go b/internal/test/cli.go
index fb1397f397a7..93ed3abe2173 100644
--- a/internal/test/cli.go
+++ b/internal/test/cli.go
@@ -215,3 +215,8 @@ func (c *FakeCli) ContentTrustEnabled() bool {
 func EnableContentTrust(c *FakeCli) {
 	c.contentTrust = true
 }
+
+// BuildKitEnabled on the fake cli
+func (c *FakeCli) BuildKitEnabled() (bool, error) {
+	return true, nil
+}

From e7a8748b939fbf7798352cff1e0b87ef26bf0002 Mon Sep 17 00:00:00 2001
From: CrazyMax <crazy-max@users.noreply.github.com>
Date: Wed, 23 Feb 2022 16:20:45 +0100
Subject: [PATCH 2/2] build: use legacy builder for wcow if not opt-in with a
 builder component

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>
---
 cmd/docker/builder.go | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/cmd/docker/builder.go b/cmd/docker/builder.go
index 03d6055b8e57..31c6076046c0 100644
--- a/cmd/docker/builder.go
+++ b/cmd/docker/builder.go
@@ -41,8 +41,7 @@ func newBuilderError(warn bool, err error) error {
 }
 
 func processBuilder(dockerCli command.Cli, cmd *cobra.Command, args, osargs []string) ([]string, []string, error) {
-	var useLegacy bool
-	var useBuilder bool
+	var useLegacy, useBuilder bool
 
 	// check DOCKER_BUILDKIT env var is present and
 	// if not assume we want to use the builder component
@@ -73,6 +72,12 @@ func processBuilder(dockerCli command.Cli, cmd *cobra.Command, args, osargs []st
 		return args, osargs, nil
 	}
 
+	// wcow build command must use the legacy builder
+	// if not opt-in through a builder component
+	if !useBuilder && dockerCli.ServerInfo().OSType == "windows" {
+		return args, osargs, nil
+	}
+
 	if useLegacy {
 		// display warning if not wcow and continue
 		if dockerCli.ServerInfo().OSType != "windows" {