Handle empty DOCKER_BUILDKIT like unset

vvoland · vvoland · commit ff7f76af7a09 · 2023-04-19T14:17:01.000+02:00
This fixes the cli erroring out if the variable is set to an empty
value.

```
$ export DOCKER_BUILDKIT=
$ docker version
DOCKER_BUILDKIT environment variable expects boolean value: strconv.ParseBool: parsing "": invalid syntax
```

Signed-off-by: Paweł Gronowski &lt;pawel.gronowski@docker.com&gt;
diff --git a/cli/command/cli.go b/cli/command/cli.go
@@ -162,8 +162,8 @@ func (cli *DockerCli) ContentTrustEnabled() bool {
 
 // 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 {
+	// use DOCKER_BUILDKIT env var value if set and not empty
+	if v := os.Getenv("DOCKER_BUILDKIT"); v != "" {
 		enabled, err := strconv.ParseBool(v)
 		if err != nil {
 			return false, errors.Wrap(err, "DOCKER_BUILDKIT environment variable expects boolean value")
diff --git a/cmd/docker/builder.go b/cmd/docker/builder.go
@@ -44,9 +44,9 @@ func processBuilder(dockerCli command.Cli, cmd *cobra.Command, args, osargs []st
 	var buildKitDisabled, useBuilder, useAlias bool
 	var envs []string
 
-	// check DOCKER_BUILDKIT env var is present and
-	// if not assume we want to use the builder component
-	if v, ok := os.LookupEnv("DOCKER_BUILDKIT"); ok {
+	// check DOCKER_BUILDKIT env var is not empty
+	// if it is assume we want to use the builder component
+	if v := os.Getenv("DOCKER_BUILDKIT"); v != "" {
 		enabled, err := strconv.ParseBool(v)
 		if err != nil {
 			return args, osargs, nil, errors.Wrap(err, "DOCKER_BUILDKIT environment variable expects boolean value")
