bake: allow overriding no-cache and pull per target via --set

README.md

@@ -566,8 +566,12 @@ docker buildx bake --set target.args.mybuildarg=value
 docker buildx bake --set target.platform=linux/arm64
 docker buildx bake --set foo*.args.mybuildarg=value	# overrides build arg for all targets starting with 'foo'
 docker buildx bake --set *.platform=linux/arm64		# overrides platform for all targets
+docker buildx bake --set foo*.no-cache                  # bypass caching only for targets starting with 'foo'
 ```
 
+Complete list of overridable fields:
+	args, cache-from, cache-to, context, dockerfile, labels, no-cache, output, platform, pull, secrets, ssh, tags, target
+
 #### File definition
 
 In addition to compose files, bake supports a JSON and an equivalent HCL file format for defining build groups and targets.
@@ -607,6 +611,8 @@ target "db" {
 }
 ```
 
+Complete list of valid target fields:
+	args, cache-from, cache-to, context, dockerfile, inherits, labels, no-cache, output, platform, pull, secrets, ssh, tags, target
 
 ### `buildx imagetools create [OPTIONS] [SOURCE] [SOURCE...]`
 

bake/bake.go

@@ -5,6 +5,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path"
+	"strconv"
 	"strings"
 
 	"github.com/docker/buildx/build"
@@ -194,6 +195,18 @@ func (c Config) newOverrides(v []string) (map[string]Target, error) {
 				t.Platforms = append(t.Platforms, parts[1])
 			case "output":
 				t.Outputs = append(t.Outputs, parts[1])
+			case "no-cache":
+				noCache, err := strconv.ParseBool(parts[1])
+				if err != nil {
+					return nil, errors.Errorf("invalid value %s for boolean key no-cache", parts[1])
+				}
+				t.NoCache = noCache
+			case "pull":
+				pull, err := strconv.ParseBool(parts[1])
+				if err != nil {
+					return nil, errors.Errorf("invalid value %s for boolean key pull", parts[1])
+				}
+				t.Pull = pull
 			default:
 				return nil, errors.Errorf("unknown key: %s", keys[1])
 			}
@@ -270,7 +283,9 @@ type Group struct {
 }
 
 type Target struct {
-	Inherits   []string          `json:"inherits,omitempty" hcl:"inherits,omitempty"`
+	// Inherits is the only field that cannot be overridden with --set
+	Inherits []string `json:"inherits,omitempty" hcl:"inherits,omitempty"`
+
 	Context    *string           `json:"context,omitempty" hcl:"context,omitempty"`
 	Dockerfile *string           `json:"dockerfile,omitempty" hcl:"dockerfile,omitempty"`
 	Args       map[string]string `json:"args,omitempty" hcl:"args,omitempty"`
@@ -283,6 +298,9 @@ type Target struct {
 	SSH        []string          `json:"ssh,omitempty" hcl:"ssh,omitempty"`
 	Platforms  []string          `json:"platforms,omitempty" hcl:"platforms,omitempty"`
 	Outputs    []string          `json:"output,omitempty" hcl:"output,omitempty"`
+	Pull       bool              `json:"pull,omitempty": hcl:"pull,omitempty"`
+	NoCache    bool              `json:"no-cache,omitempty": hcl:"no-cache,omitempty"`
+	// IMPORTANT: if you add more fields here, do not forget to update newOverrides and README.
 }
 
 func (t *Target) normalize() {
@@ -295,10 +313,10 @@ func (t *Target) normalize() {
 	t.Outputs = removeDupes(t.Outputs)
 }
 
-func TargetsToBuildOpt(m map[string]Target, noCache, pull bool) (map[string]build.Options, error) {
+func TargetsToBuildOpt(m map[string]Target) (map[string]build.Options, error) {
 	m2 := make(map[string]build.Options, len(m))
 	for k, v := range m {
-		bo, err := toBuildOpt(v, noCache, pull)
+		bo, err := toBuildOpt(v)
 		if err != nil {
 			return nil, err
 		}
@@ -307,7 +325,7 @@ func TargetsToBuildOpt(m map[string]Target, noCache, pull bool) (map[string]buil
 	return m2, nil
 }
 
-func toBuildOpt(t Target, noCache, pull bool) (*build.Options, error) {
+func toBuildOpt(t Target) (*build.Options, error) {
 	if v := t.Context; v != nil && *v == "-" {
 		return nil, errors.Errorf("context from stdin not allowed in bake")
 	}
@@ -336,8 +354,8 @@ func toBuildOpt(t Target, noCache, pull bool) (*build.Options, error) {
 		Tags:      t.Tags,
 		BuildArgs: t.Args,
 		Labels:    t.Labels,
-		NoCache:   noCache,
-		Pull:      pull,
+		NoCache:   t.NoCache,
+		Pull:      t.Pull,
 	}
 
 	platforms, err := platformutil.Parse(t.Platforms)

commands/bake.go

@@ -46,6 +46,12 @@ func runBake(dockerCli command.Cli, targets []string, in bakeOptions) error {
 	} else if in.exportLoad {
 		overrides = append(overrides, "*.output=type=docker")
 	}
+	if in.noCache != nil {
+		overrides = append(overrides, fmt.Sprintf("*.no-cache=%t", *in.noCache))
+	}
+	if in.pull != nil {
+		overrides = append(overrides, fmt.Sprintf("*.pull=%t", *in.pull))
+	}
 
 	m, err := bake.ReadTargets(ctx, in.files, targets, overrides)
 	if err != nil {
@@ -61,7 +67,7 @@ func runBake(dockerCli command.Cli, targets []string, in bakeOptions) error {
 		return nil
 	}
 
-	bo, err := bake.TargetsToBuildOpt(m, in.noCache, in.pull)
+	bo, err := bake.TargetsToBuildOpt(m)
 	if err != nil {
 		return err
 	}

commands/build.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	"github.com/docker/buildx/build"
+	"github.com/docker/buildx/util/flagutil"
 	"github.com/docker/buildx/util/platformutil"
 	"github.com/docker/buildx/util/progress"
 	"github.com/docker/cli/cli"
@@ -62,9 +63,9 @@ type buildOptions struct {
 }
 
 type commonOptions struct {
-	noCache    bool
+	noCache    *bool
 	progress   string
-	pull       bool
+	pull       *bool
 	exportPush bool
 	exportLoad bool
 }
@@ -79,6 +80,15 @@ func runBuild(dockerCli command.Cli, in buildOptions) error {
 
 	ctx := appcontext.Context()
 
+	noCache := false
+	if in.noCache != nil {
+		noCache = *in.noCache
+	}
+	pull := false
+	if in.pull != nil {
+		pull = *in.pull
+	}
+
 	opts := build.Options{
 		Inputs: build.Inputs{
 			ContextPath:    in.contextPath,
@@ -88,8 +98,8 @@ func runBuild(dockerCli command.Cli, in buildOptions) error {
 		Tags:        in.tags,
 		Labels:      listToMap(in.labels, false),
 		BuildArgs:   listToMap(in.buildArgs, true),
-		Pull:        in.pull,
-		NoCache:     in.noCache,
+		Pull:        pull,
+		NoCache:     noCache,
 		Target:      in.target,
 		ImageIDFile: in.imageIDFile,
 		ExtraHosts:  in.extraHosts,
@@ -293,9 +303,9 @@ func buildCmd(dockerCli command.Cli) *cobra.Command {
 }
 
 func commonFlags(options *commonOptions, flags *pflag.FlagSet) {
-	flags.BoolVar(&options.noCache, "no-cache", false, "Do not use cache when building the image")
+	flags.Var(flagutil.Tristate(options.noCache), "no-cache", "Do not use cache when building the image")
 	flags.StringVar(&options.progress, "progress", "auto", "Set type of progress output (auto, plain, tty). Use plain to show container output")
-	flags.BoolVar(&options.pull, "pull", false, "Always attempt to pull a newer version of the image")
+	flags.Var(flagutil.Tristate(options.pull), "pull", "Always attempt to pull a newer version of the image")
 }
 
 func listToMap(values []string, defaultEnv bool) map[string]string {

util/flagutil/flagutil.go

@@ -0,0 +1,36 @@
+package flagutil
+
+import "strconv"
+
+type tristate struct {
+	opt *bool
+}
+
+// Tristate is a tri-state boolean flag type.
+// It can be set, but not unset.
+func Tristate(opt *bool) tristate {
+	return tristate{opt}
+}
+
+func (t tristate) Type() string {
+	return "tristate"
+}
+
+func (t tristate) String() string {
+	if t.opt == nil {
+		return "(unset)"
+	}
+	if *t.opt {
+		return "true"
+	}
+	return "false"
+}
+
+func (t tristate) Set(s string) error {
+	b, err := strconv.ParseBool(s)
+	if err != nil {
+		return err
+	}
+	t.opt = &b
+	return nil
+}