Allow using key-value data

cmd/docker-buildx/config.go

@@ -159,11 +159,11 @@ func settingsFlags(settings *plugin.Settings) []cli.Flag {
 			Value:       true,
 			Destination: &settings.Build.LabelsAuto,
 		},
-		&cli.StringSliceFlag{
+		&cli.StringFlag{
 			Name:        "args",
 			EnvVars:     []string{"PLUGIN_BUILD_ARGS"},
-			Usage:       "sets custom build arguments for the build",
-			Destination: &settings.Build.Args,
+			Usage:       "sets custom build arguments for the build. Must be a JSON string",
+			Destination: &settings.Build.ArgsRaw,
 		},
 		&cli.StringSliceFlag{
 			Name:        "args-from-env",

cmd/docker-buildx/main.go

@@ -19,7 +19,7 @@ func main() {
 	if _, err := os.Stat("/run/drone/env"); err == nil {
 		godotenv.Overload("/run/drone/env")
 	}
-	
+
 	if envFile, set := os.LookupEnv("PLUGIN_ENV_FILE"); set {
 		godotenv.Overload(envFile)
 	}

plugin/impl.go

@@ -58,6 +58,7 @@ type Build struct {
 	LabelsAuto      bool            // Docker build auto labels
 	Labels          cli.StringSlice // Docker build labels
 	Platforms       cli.StringSlice // Docker build target platforms
+	ArgsRaw         string          // Docker build args (as JSON)
 	Args            cli.StringSlice // Docker build args
 	ArgsEnv         cli.StringSlice // Docker build args from env
 	Target          string          // Docker build target
@@ -87,6 +88,26 @@ func (l Login) anonymous() bool {
 	return l.Username == "" || l.Password == ""
 }
 
+// Parse the provided build args into b.Args
+func (b Build) BuildArgs() {
+	if len(b.ArgsRaw) > 0 {
+		buildArgsRaw := map[string]string{}
+		err := json.Unmarshal([]byte(b.ArgsRaw), &buildArgsRaw)
+		if err != nil {
+			fmt.Printf("Failed to parse build args: %s", err)
+		}
+
+		for key, value := range buildArgsRaw {
+			b.Args = *cli.NewStringSlice(
+				append(
+					b.Args.Value(),
+					fmt.Sprintf("%s=%s", key, value),
+				)...,
+			)
+		}
+	}
+}
+
 // Init initialise plugin settings
 func (p *Plugin) InitSettings() error {
 	if p.settings.LoginsRaw != "" {
@@ -227,6 +248,8 @@ func (p *Plugin) writeBuildkitConfig() error {
 
 // Execute provides the implementation of the plugin.
 func (p *Plugin) Execute() error {
+	p.settings.Build.BuildArgs()
+
 	// start the Docker daemon server
 	if !p.settings.Daemon.Disabled {
 		// If no custom DNS value set start internal DNS server