Merge pull request #2556 from tonistiigi/bake-call

bake: add call methods support and printing

bake/bake.go

@@ -177,7 +177,7 @@ func readWithProgress(r io.Reader, setStatus func(st *client.VertexStatus)) (dt
 }
 
 func ListTargets(files []File) ([]string, error) {
-	c, err := ParseFiles(files, nil)
+	c, _, err := ParseFiles(files, nil)
 	if err != nil {
 		return nil, err
 	}
@@ -192,7 +192,7 @@ func ListTargets(files []File) ([]string, error) {
 }
 
 func ReadTargets(ctx context.Context, files []File, targets, overrides []string, defaults map[string]string) (map[string]*Target, map[string]*Group, error) {
-	c, err := ParseFiles(files, defaults)
+	c, _, err := ParseFiles(files, defaults)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -298,7 +298,7 @@ func sliceToMap(env []string) (res map[string]string) {
 	return
 }
 
-func ParseFiles(files []File, defaults map[string]string) (_ *Config, err error) {
+func ParseFiles(files []File, defaults map[string]string) (_ *Config, _ *hclparser.ParseMeta, err error) {
 	defer func() {
 		err = formatHCLError(err, files)
 	}()
@@ -310,7 +310,7 @@ func ParseFiles(files []File, defaults map[string]string) (_ *Config, err error)
 		isCompose, composeErr := validateComposeFile(f.Data, f.Name)
 		if isCompose {
 			if composeErr != nil {
-				return nil, composeErr
+				return nil, nil, composeErr
 			}
 			composeFiles = append(composeFiles, f)
 		}
@@ -318,13 +318,13 @@ func ParseFiles(files []File, defaults map[string]string) (_ *Config, err error)
 			hf, isHCL, err := ParseHCLFile(f.Data, f.Name)
 			if isHCL {
 				if err != nil {
-					return nil, err
+					return nil, nil, err
 				}
 				hclFiles = append(hclFiles, hf)
 			} else if composeErr != nil {
-				return nil, errors.Wrapf(err, "failed to parse %s: parsing yaml: %v, parsing hcl", f.Name, composeErr)
+				return nil, nil, errors.Wrapf(err, "failed to parse %s: parsing yaml: %v, parsing hcl", f.Name, composeErr)
 			} else {
-				return nil, err
+				return nil, nil, err
 			}
 		}
 	}
@@ -332,23 +332,24 @@ func ParseFiles(files []File, defaults map[string]string) (_ *Config, err error)
 	if len(composeFiles) > 0 {
 		cfg, cmperr := ParseComposeFiles(composeFiles)
 		if cmperr != nil {
-			return nil, errors.Wrap(cmperr, "failed to parse compose file")
+			return nil, nil, errors.Wrap(cmperr, "failed to parse compose file")
 		}
 		c = mergeConfig(c, *cfg)
 		c = dedupeConfig(c)
 	}
 
+	var pm hclparser.ParseMeta
 	if len(hclFiles) > 0 {
-		renamed, err := hclparser.Parse(hclparser.MergeFiles(hclFiles), hclparser.Opt{
+		res, err := hclparser.Parse(hclparser.MergeFiles(hclFiles), hclparser.Opt{
 			LookupVar:     os.LookupEnv,
 			Vars:          defaults,
 			ValidateLabel: validateTargetName,
 		}, &c)
 		if err.HasErrors() {
-			return nil, err
+			return nil, nil, err
 		}
 
-		for _, renamed := range renamed {
+		for _, renamed := range res.Renamed {
 			for oldName, newNames := range renamed {
 				newNames = dedupSlice(newNames)
 				if len(newNames) == 1 && oldName == newNames[0] {
@@ -361,9 +362,10 @@ func ParseFiles(files []File, defaults map[string]string) (_ *Config, err error)
 			}
 		}
 		c = dedupeConfig(c)
+		pm = *res
 	}
 
-	return &c, nil
+	return &c, &pm, nil
 }
 
 func dedupeConfig(c Config) Config {
@@ -388,7 +390,8 @@ func dedupeConfig(c Config) Config {
 }
 
 func ParseFile(dt []byte, fn string) (*Config, error) {
-	return ParseFiles([]File{{Data: dt, Name: fn}}, nil)
+	c, _, err := ParseFiles([]File{{Data: dt, Name: fn}}, nil)
+	return c, err
 }
 
 type Config struct {
@@ -670,12 +673,14 @@ func (c Config) target(name string, visited map[string]*Target, overrides map[st
 
 type Group struct {
 	Name        string   `json:"-" hcl:"name,label" cty:"name"`
+	Description string   `json:"description,omitempty" hcl:"description,optional" cty:"description"`
 	Targets     []string `json:"targets" hcl:"targets" cty:"targets"`
 	// Target // TODO?
 }
 
 type Target struct {
 	Name        string `json:"-" hcl:"name,label" cty:"name"`
+	Description string `json:"description,omitempty" hcl:"description,optional" cty:"description"`
 
 	// Inherits is the only field that cannot be overridden with --set
 	Inherits []string `json:"inherits,omitempty" hcl:"inherits,optional" cty:"inherits"`
@@ -702,7 +707,8 @@ type Target struct {
 	NoCacheFilter    []string           `json:"no-cache-filter,omitempty" hcl:"no-cache-filter,optional" cty:"no-cache-filter"`
 	ShmSize          *string            `json:"shm-size,omitempty" hcl:"shm-size,optional"`
 	Ulimits          []string           `json:"ulimits,omitempty" hcl:"ulimits,optional"`
-	// IMPORTANT: if you add more fields here, do not forget to update newOverrides and docs/bake-reference.md.
+	Call             *string            `json:"call,omitempty" hcl:"call,optional" cty:"call"`
+	// IMPORTANT: if you add more fields here, do not forget to update newOverrides/AddOverrides and docs/bake-reference.md.
 
 	// linked is a private field to mark a target used as a linked one
 	linked bool
@@ -776,6 +782,9 @@ func (t *Target) Merge(t2 *Target) {
 	if t2.Target != nil {
 		t.Target = t2.Target
 	}
+	if t2.Call != nil {
+		t.Call = t2.Call
+	}
 	if t2.Annotations != nil { // merge
 		t.Annotations = append(t.Annotations, t2.Annotations...)
 	}
@@ -819,6 +828,9 @@ func (t *Target) Merge(t2 *Target) {
 	if t2.Ulimits != nil { // merge
 		t.Ulimits = append(t.Ulimits, t2.Ulimits...)
 	}
+	if t2.Description != "" {
+		t.Description = t2.Description
+	}
 	t.Inherits = append(t.Inherits, t2.Inherits...)
 }
 
@@ -863,6 +875,8 @@ func (t *Target) AddOverrides(overrides map[string]Override) error {
 			t.CacheTo = o.ArrValue
 		case "target":
 			t.Target = &value
+		case "call":
+			t.Call = &value
 		case "secrets":
 			t.Secrets = o.ArrValue
 		case "ssh":
@@ -1298,6 +1312,12 @@ func toBuildOpt(t *Target, inp *Input) (*build.Options, error) {
 		bo.Target = *t.Target
 	}
 
+	if t.Call != nil {
+		bo.PrintFunc = &build.PrintFunc{
+			Name: *t.Call,
+		}
+	}
+
 	cacheImports, err := buildflags.ParseCacheEntry(t.CacheFrom)
 	if err != nil {
 		return nil, err

bake/bake_test.go

@@ -1528,7 +1528,7 @@ services:
         v2: "bar"
 `)
 
-	c, err := ParseFiles([]File{
+	c, _, err := ParseFiles([]File{
 		{Data: dt, Name: "c1.foo"},
 		{Data: dt2, Name: "c2.bar"},
 	}, nil)

bake/hcl_test.go

@@ -273,7 +273,7 @@ func TestHCLMultiFileSharedVariables(t *testing.T) {
 		}
 		`)
 
-	c, err := ParseFiles([]File{
+	c, _, err := ParseFiles([]File{
 		{Data: dt, Name: "c1.hcl"},
 		{Data: dt2, Name: "c2.hcl"},
 	}, nil)
@@ -285,7 +285,7 @@ func TestHCLMultiFileSharedVariables(t *testing.T) {
 
 	t.Setenv("FOO", "def")
 
-	c, err = ParseFiles([]File{
+	c, _, err = ParseFiles([]File{
 		{Data: dt, Name: "c1.hcl"},
 		{Data: dt2, Name: "c2.hcl"},
 	}, nil)
@@ -322,7 +322,7 @@ func TestHCLVarsWithVars(t *testing.T) {
 		}
 		`)
 
-	c, err := ParseFiles([]File{
+	c, _, err := ParseFiles([]File{
 		{Data: dt, Name: "c1.hcl"},
 		{Data: dt2, Name: "c2.hcl"},
 	}, nil)
@@ -334,7 +334,7 @@ func TestHCLVarsWithVars(t *testing.T) {
 
 	t.Setenv("BASE", "new")
 
-	c, err = ParseFiles([]File{
+	c, _, err = ParseFiles([]File{
 		{Data: dt, Name: "c1.hcl"},
 		{Data: dt2, Name: "c2.hcl"},
 	}, nil)
@@ -612,7 +612,7 @@ func TestHCLMultiFileAttrs(t *testing.T) {
 		FOO="def"
 		`)
 
-	c, err := ParseFiles([]File{
+	c, _, err := ParseFiles([]File{
 		{Data: dt, Name: "c1.hcl"},
 		{Data: dt2, Name: "c2.hcl"},
 	}, nil)
@@ -623,7 +623,7 @@ func TestHCLMultiFileAttrs(t *testing.T) {
 
 	t.Setenv("FOO", "ghi")
 
-	c, err = ParseFiles([]File{
+	c, _, err = ParseFiles([]File{
 		{Data: dt, Name: "c1.hcl"},
 		{Data: dt2, Name: "c2.hcl"},
 	}, nil)
@@ -647,7 +647,7 @@ func TestHCLMultiFileGlobalAttrs(t *testing.T) {
 		FOO = "def"
 		`)
 
-	c, err := ParseFiles([]File{
+	c, _, err := ParseFiles([]File{
 		{Data: dt, Name: "c1.hcl"},
 		{Data: dt2, Name: "c2.hcl"},
 	}, nil)
@@ -830,7 +830,7 @@ func TestHCLRenameMultiFile(t *testing.T) {
 		}
 		`)
 
-	c, err := ParseFiles([]File{
+	c, _, err := ParseFiles([]File{
 		{Data: dt, Name: "c1.hcl"},
 		{Data: dt2, Name: "c2.hcl"},
 		{Data: dt3, Name: "c3.hcl"},
@@ -1050,7 +1050,7 @@ func TestHCLMatrixArgsOverride(t *testing.T) {
 	}
 	`)
 
-	c, err := ParseFiles([]File{
+	c, _, err := ParseFiles([]File{
 		{Data: dt, Name: "docker-bake.hcl"},
 	}, map[string]string{"ABC": "11,22,33"})
 	require.NoError(t, err)
@@ -1236,7 +1236,7 @@ services:
         v2: "bar"
 `)
 
-	c, err := ParseFiles([]File{
+	c, _, err := ParseFiles([]File{
 		{Data: dt, Name: "c1.hcl"},
 		{Data: dt2, Name: "c2.yml"},
 	}, nil)
@@ -1258,7 +1258,7 @@ func TestHCLBuiltinVars(t *testing.T) {
 		}
 		`)
 
-	c, err := ParseFiles([]File{
+	c, _, err := ParseFiles([]File{
 		{Data: dt, Name: "c1.hcl"},
 	}, map[string]string{
 		"BAKE_CMD_CONTEXT": "foo",
@@ -1272,7 +1272,7 @@ func TestHCLBuiltinVars(t *testing.T) {
 }
 
 func TestCombineHCLAndJSONTargets(t *testing.T) {
-	c, err := ParseFiles([]File{
+	c, _, err := ParseFiles([]File{
 		{
 			Name: "docker-bake.hcl",
 			Data: []byte(`
@@ -1348,7 +1348,7 @@ target "b" {
 }
 
 func TestCombineHCLAndJSONVars(t *testing.T) {
-	c, err := ParseFiles([]File{
+	c, _, err := ParseFiles([]File{
 		{
 			Name: "docker-bake.hcl",
 			Data: []byte(`

bake/hclparser/hclparser.go

@@ -27,7 +27,9 @@ type Opt struct {
 type variable struct {
 	Name        string         `json:"-" hcl:"name,label"`
 	Default     *hcl.Attribute `json:"default,omitempty" hcl:"default,optional"`
+	Description string         `json:"description,omitempty" hcl:"description,optional"`
 	Body        hcl.Body       `json:"-" hcl:",body"`
+	Remain      hcl.Body       `json:"-" hcl:",remain"`
 }
 
 type functionDef struct {
@@ -534,7 +536,18 @@ func (p *parser) resolveBlockNames(block *hcl.Block) ([]string, error) {
 	return names, nil
 }
 
-func Parse(b hcl.Body, opt Opt, val interface{}) (map[string]map[string][]string, hcl.Diagnostics) {
+type Variable struct {
+	Name        string
+	Description string
+	Value       *string
+}
+
+type ParseMeta struct {
+	Renamed      map[string]map[string][]string
+	AllVariables []*Variable
+}
+
+func Parse(b hcl.Body, opt Opt, val interface{}) (*ParseMeta, hcl.Diagnostics) {
 	reserved := map[string]struct{}{}
 	schema, _ := gohcl.ImpliedBodySchema(val)
 
@@ -643,6 +656,7 @@ func Parse(b hcl.Body, opt Opt, val interface{}) (map[string]map[string][]string
 		}
 	}
 
+	vars := make([]*Variable, 0, len(p.vars))
 	for k := range p.vars {
 		if err := p.resolveValue(p.ectx, k); err != nil {
 			if diags, ok := err.(hcl.Diagnostics); ok {
@@ -651,6 +665,21 @@ func Parse(b hcl.Body, opt Opt, val interface{}) (map[string]map[string][]string
 			r := p.vars[k].Body.MissingItemRange()
 			return nil, wrapErrorDiagnostic("Invalid value", err, &r, &r)
 		}
+		v := &Variable{
+			Name:        p.vars[k].Name,
+			Description: p.vars[k].Description,
+		}
+		if vv := p.ectx.Variables[k]; !vv.IsNull() {
+			var s string
+			switch vv.Type() {
+			case cty.String:
+				s = vv.AsString()
+			case cty.Bool:
+				s = strconv.FormatBool(vv.True())
+			}
+			v.Value = &s
+		}
+		vars = append(vars, v)
 	}
 
 	for k := range p.funcs {
@@ -795,7 +824,10 @@ func Parse(b hcl.Body, opt Opt, val interface{}) (map[string]map[string][]string
 		}
 	}
 
-	return renamed, nil
+	return &ParseMeta{
+		Renamed:      renamed,
+		AllVariables: vars,
+	}, nil
 }
 
 // wrapErrorDiagnostic wraps an error into a hcl.Diagnostics object.

bake/hclparser/merged.go

@@ -111,7 +111,6 @@ func (mb mergedBodies) JustAttributes() (hcl.Attributes, hcl.Diagnostics) {
 			diags = append(diags, thisDiags...)
 		}
 
-		if thisAttrs != nil {
 		for name, attr := range thisAttrs {
 			if existing := attrs[name]; existing != nil {
 				diags = diags.Append(&hcl.Diagnostic{
@@ -127,7 +126,6 @@ func (mb mergedBodies) JustAttributes() (hcl.Attributes, hcl.Diagnostics) {
 			attrs[name] = attr
 		}
 	}
-	}
 
 	return attrs, diags
 }

commands/bake.go

@@ -1,20 +1,27 @@
 package commands
 
 import (
+	"bytes"
+	"cmp"
 	"context"
 	"encoding/json"
 	"fmt"
 	"io"
 	"os"
+	"slices"
 	"strings"
+	"text/tabwriter"
 
 	"github.com/containerd/console"
 	"github.com/containerd/platforms"
 	"github.com/docker/buildx/bake"
+	"github.com/docker/buildx/bake/hclparser"
 	"github.com/docker/buildx/build"
 	"github.com/docker/buildx/builder"
+	"github.com/docker/buildx/controller/pb"
 	"github.com/docker/buildx/localstate"
 	"github.com/docker/buildx/util/buildflags"
+	"github.com/docker/buildx/util/cobrautil"
 	"github.com/docker/buildx/util/cobrautil/completion"
 	"github.com/docker/buildx/util/confutil"
 	"github.com/docker/buildx/util/desktop"
@@ -33,6 +40,8 @@ type bakeOptions struct {
 	files       []string
 	overrides   []string
 	printOnly   bool
+	listTargets bool
+	listVars    bool
 	sbom        string
 	provenance  string
 
@@ -40,6 +49,7 @@ type bakeOptions struct {
 	metadataFile string
 	exportPush   bool
 	exportLoad   bool
+	callFunc     string
 }
 
 func runBake(ctx context.Context, dockerCli command.Cli, targets []string, in bakeOptions, cFlags commonFlags) (err error) {
@@ -71,6 +81,11 @@ func runBake(ctx context.Context, dockerCli command.Cli, targets []string, in ba
 		targets = []string{"default"}
 	}
 
+	callFunc, err := buildflags.ParsePrintFunc(in.callFunc)
+	if err != nil {
+		return err
+	}
+
 	overrides := in.overrides
 	if in.exportPush {
 		overrides = append(overrides, "*.push=true")
@@ -78,6 +93,9 @@ func runBake(ctx context.Context, dockerCli command.Cli, targets []string, in ba
 	if in.exportLoad {
 		overrides = append(overrides, "*.load=true")
 	}
+	if callFunc != nil {
+		overrides = append(overrides, fmt.Sprintf("*.call=%s", callFunc.Name))
+	}
 	if cFlags.noCache != nil {
 		overrides = append(overrides, fmt.Sprintf("*.no-cache=%t", *cFlags.noCache))
 	}
@@ -171,12 +189,32 @@ func runBake(ctx context.Context, dockerCli command.Cli, targets []string, in ba
 		return errors.New("couldn't find a bake definition")
 	}
 
-	tgts, grps, err := bake.ReadTargets(ctx, files, targets, overrides, map[string]string{
+	defaults := map[string]string{
 		// don't forget to update documentation if you add a new
 		// built-in variable: docs/bake-reference.md#built-in-variables
 		"BAKE_CMD_CONTEXT":    cmdContext,
 		"BAKE_LOCAL_PLATFORM": platforms.Format(platforms.DefaultSpec()),
-	})
+	}
+
+	if in.listTargets || in.listVars {
+		cfg, pm, err := bake.ParseFiles(files, defaults)
+		if err != nil {
+			return err
+		}
+
+		err = printer.Wait()
+		printer = nil
+		if err != nil {
+			return err
+		}
+		if in.listTargets {
+			return printTargetList(dockerCli.Out(), cfg)
+		} else if in.listVars {
+			return printVars(dockerCli.Out(), pm.AllVariables)
+		}
+	}
+
+	tgts, grps, err := bake.ReadTargets(ctx, files, targets, overrides, defaults)
 	if err != nil {
 		return err
 	}
@@ -222,6 +260,16 @@ func runBake(ctx context.Context, dockerCli command.Cli, targets []string, in ba
 		return nil
 	}
 
+	for _, opt := range bo {
+		if opt.PrintFunc != nil {
+			cf, err := buildflags.ParsePrintFunc(opt.PrintFunc.Name)
+			if err != nil {
+				return err
+			}
+			opt.PrintFunc.Name = cf.Name
+		}
+	}
+
 	prm := confutil.MetadataProvenance()
 	if len(in.metadataFile) == 0 {
 		prm = confutil.MetadataProvenanceModeDisabled
@@ -254,7 +302,117 @@ func runBake(ctx context.Context, dockerCli command.Cli, targets []string, in ba
 		return wrapBuildError(err, true)
 	}
 
-	return
+	err = printer.Wait()
+	if err != nil {
+		return err
+	}
+
+	var callFormatJSON bool
+	var jsonResults = map[string]map[string]any{}
+	if callFunc != nil {
+		callFormatJSON = callFunc.Format == "json"
+	}
+	var sep bool
+	var exitCode int
+
+	names := make([]string, 0, len(bo))
+	for name := range bo {
+		names = append(names, name)
+	}
+	slices.Sort(names)
+
+	for _, name := range names {
+		req := bo[name]
+		if req.PrintFunc == nil {
+			continue
+		}
+
+		pf := &pb.PrintFunc{
+			Name:         req.PrintFunc.Name,
+			Format:       req.PrintFunc.Format,
+			IgnoreStatus: req.PrintFunc.IgnoreStatus,
+		}
+
+		if callFunc != nil {
+			pf.Format = callFunc.Format
+			pf.IgnoreStatus = callFunc.IgnoreStatus
+		}
+
+		var res map[string]string
+		if sp, ok := resp[name]; ok {
+			res = sp.ExporterResponse
+		}
+
+		if callFormatJSON {
+			jsonResults[name] = map[string]any{}
+			buf := &bytes.Buffer{}
+			if code, err := printResult(buf, pf, res); err != nil {
+				jsonResults[name]["error"] = err.Error()
+				exitCode = 1
+			} else if code != 0 && exitCode == 0 {
+				exitCode = code
+			}
+			m := map[string]*json.RawMessage{}
+			if err := json.Unmarshal(buf.Bytes(), &m); err == nil {
+				for k, v := range m {
+					jsonResults[name][k] = v
+				}
+			} else {
+				jsonResults[name][pf.Name] = json.RawMessage(buf.Bytes())
+			}
+		} else {
+			if sep {
+				fmt.Fprintln(dockerCli.Out())
+			} else {
+				sep = true
+			}
+			fmt.Fprintf(dockerCli.Out(), "%s\n", name)
+			if descr := tgts[name].Description; descr != "" {
+				fmt.Fprintf(dockerCli.Out(), "%s\n", descr)
+			}
+
+			fmt.Fprintln(dockerCli.Out())
+			if code, err := printResult(dockerCli.Out(), pf, res); err != nil {
+				fmt.Fprintf(dockerCli.Out(), "error: %v\n", err)
+				exitCode = 1
+			} else if code != 0 && exitCode == 0 {
+				exitCode = code
+			}
+		}
+	}
+	if callFormatJSON {
+		out := struct {
+			Group  map[string]*bake.Group    `json:"group,omitempty"`
+			Target map[string]map[string]any `json:"target"`
+		}{
+			Group:  grps,
+			Target: map[string]map[string]any{},
+		}
+
+		for name, def := range tgts {
+			out.Target[name] = map[string]any{
+				"build": def,
+			}
+			if res, ok := jsonResults[name]; ok {
+				printName := bo[name].PrintFunc.Name
+				if printName == "lint" {
+					printName = "check"
+				}
+				out.Target[name][printName] = res
+			}
+		}
+		dt, err := json.MarshalIndent(out, "", "  ")
+		if err != nil {
+			return err
+		}
+		fmt.Fprintln(dockerCli.Out(), string(dt))
+	}
+
+	if exitCode != 0 {
+		os.Exit(exitCode)
+	}
+
+	return nil
 }
 
 func bakeCmd(dockerCli command.Cli, rootOpts *rootOptions) *cobra.Command {
@@ -290,6 +448,18 @@ func bakeCmd(dockerCli command.Cli, rootOpts *rootOptions) *cobra.Command {
 	flags.StringVar(&options.sbom, "sbom", "", `Shorthand for "--set=*.attest=type=sbom"`)
 	flags.StringVar(&options.provenance, "provenance", "", `Shorthand for "--set=*.attest=type=provenance"`)
 	flags.StringArrayVar(&options.overrides, "set", nil, `Override target value (e.g., "targetpattern.key=value")`)
+	flags.StringVar(&options.callFunc, "call", "build", `Set method for evaluating build ("check", "outline", "targets")`)
+
+	flags.VarPF(callAlias(&options.callFunc, "check"), "check", "", `Shorthand for "--call=check"`)
+	flags.Lookup("check").NoOptDefVal = "true"
+
+	flags.BoolVar(&options.listTargets, "list-targets", false, "List available targets")
+	cobrautil.MarkFlagsExperimental(flags, "list-targets")
+	flags.MarkHidden("list-targets")
+
+	flags.BoolVar(&options.listVars, "list-variables", false, "List defined variables")
+	cobrautil.MarkFlagsExperimental(flags, "list-variables")
+	flags.MarkHidden("list-variables")
 
 	commonBuildFlags(&cFlags, flags)
 
@@ -346,3 +516,75 @@ func readBakeFiles(ctx context.Context, nodes []builder.Node, url string, names
 
 	return
 }
+
+func printVars(w io.Writer, vars []*hclparser.Variable) error {
+	slices.SortFunc(vars, func(a, b *hclparser.Variable) int {
+		return cmp.Compare(a.Name, b.Name)
+	})
+	tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0)
+	defer tw.Flush()
+
+	tw.Write([]byte("VARIABLE\tVALUE\tDESCRIPTION\n"))
+
+	for _, v := range vars {
+		var value string
+		if v.Value != nil {
+			value = *v.Value
+		} else {
+			value = "<null>"
+		}
+		fmt.Fprintf(tw, "%s\t%s\t%s\n", v.Name, value, v.Description)
+	}
+	return nil
+}
+
+func printTargetList(w io.Writer, cfg *bake.Config) error {
+	tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0)
+	defer tw.Flush()
+
+	tw.Write([]byte("TARGET\tDESCRIPTION\n"))
+
+	type targetOrGroup struct {
+		name   string
+		target *bake.Target
+		group  *bake.Group
+	}
+
+	list := make([]targetOrGroup, 0, len(cfg.Targets)+len(cfg.Groups))
+	for _, tgt := range cfg.Targets {
+		list = append(list, targetOrGroup{name: tgt.Name, target: tgt})
+	}
+	for _, grp := range cfg.Groups {
+		list = append(list, targetOrGroup{name: grp.Name, group: grp})
+	}
+
+	slices.SortFunc(list, func(a, b targetOrGroup) int {
+		return cmp.Compare(a.name, b.name)
+	})
+
+	for _, tgt := range list {
+		if strings.HasPrefix(tgt.name, "_") {
+			// convention for a private target
+			continue
+		}
+		var descr string
+		if tgt.target != nil {
+			descr = tgt.target.Description
+		} else if tgt.group != nil {
+			descr = tgt.group.Description
+
+			if len(tgt.group.Targets) > 0 {
+				slices.Sort(tgt.group.Targets)
+				names := strings.Join(tgt.group.Targets, ", ")
+				if descr != "" {
+					descr += " (" + names + ")"
+				} else {
+					descr = names
+				}
+			}
+		}
+		fmt.Fprintf(tw, "%s\t%s\n", tgt.name, descr)
+	}
+
+	return nil
+}

commands/build.go

@@ -9,7 +9,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"log"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -369,8 +368,10 @@ func runBuild(ctx context.Context, dockerCli command.Cli, options buildOptions)
 		}
 	}
 	if opts.PrintFunc != nil {
-		if err := printResult(opts.PrintFunc, resp.ExporterResponse); err != nil {
+		if exitcode, err := printResult(dockerCli.Out(), opts.PrintFunc, resp.ExporterResponse); err != nil {
 			return err
+		} else if exitcode != 0 {
+			os.Exit(exitcode)
 		}
 	} else if options.metadataFile != "" {
 		dt := decodeExporterResponse(resp.ExporterResponse)
@@ -634,7 +635,7 @@ func buildCmd(dockerCli command.Cli, rootOpts *rootOptions, debugConfig *debug.D
 	}
 
 	flags.StringVar(&options.printFunc, "call", "build", `Set method for evaluating build ("check", "outline", "targets")`)
-	flags.VarPF(callAlias(options, "check"), "check", "", `Shorthand for "--call=check"`)
+	flags.VarPF(callAlias(&options.printFunc, "check"), "check", "", `Shorthand for "--call=check"`)
 	flags.Lookup("check").NoOptDefVal = "true"
 
 	// hidden flags
@@ -862,24 +863,24 @@ func printWarnings(w io.Writer, warnings []client.VertexWarning, mode progressui
 	}
 }
 
-func printResult(f *controllerapi.PrintFunc, res map[string]string) error {
+func printResult(w io.Writer, f *controllerapi.PrintFunc, res map[string]string) (int, error) {
 	switch f.Name {
 	case "outline":
-		return printValue(outline.PrintOutline, outline.SubrequestsOutlineDefinition.Version, f.Format, res)
+		return 0, printValue(w, outline.PrintOutline, outline.SubrequestsOutlineDefinition.Version, f.Format, res)
 	case "targets":
-		return printValue(targets.PrintTargets, targets.SubrequestsTargetsDefinition.Version, f.Format, res)
+		return 0, printValue(w, targets.PrintTargets, targets.SubrequestsTargetsDefinition.Version, f.Format, res)
 	case "subrequests.describe":
-		return printValue(subrequests.PrintDescribe, subrequests.SubrequestsDescribeDefinition.Version, f.Format, res)
+		return 0, printValue(w, subrequests.PrintDescribe, subrequests.SubrequestsDescribeDefinition.Version, f.Format, res)
 	case "lint":
-		err := printValue(lint.PrintLintViolations, lint.SubrequestLintDefinition.Version, f.Format, res)
+		err := printValue(w, lint.PrintLintViolations, lint.SubrequestLintDefinition.Version, f.Format, res)
 		if err != nil {
-			return err
+			return 0, err
 		}
 
 		lintResults := lint.LintResults{}
 		if result, ok := res["result.json"]; ok {
 			if err := json.Unmarshal([]byte(result), &lintResults); err != nil {
-				return err
+				return 0, err
 			}
 		}
 		if lintResults.Error != nil {
@@ -889,52 +890,51 @@ func printResult(f *controllerapi.PrintFunc, res map[string]string) error {
 			// but here we want to print the error in a way that's consistent with how
 			// the lint warnings are printed via the `lint.PrintLintViolations` function,
 			// which differs from the default error printing.
-			fmt.Println()
+			if f.Format != "json" && len(lintResults.Warnings) > 0 {
-			lintBuf := bytes.NewBuffer([]byte(lintResults.Error.Message))
+				fmt.Fprintln(w)
-			if f.Format != "json" {
-				fmt.Fprintln(lintBuf)
 			}
+			lintBuf := bytes.NewBuffer([]byte(lintResults.Error.Message + "\n"))
 			sourceInfo := lintResults.Sources[lintResults.Error.Location.SourceIndex]
 			source := errdefs.Source{
 				Info:   sourceInfo,
 				Ranges: lintResults.Error.Location.Ranges,
 			}
 			source.Print(lintBuf)
-			return errors.New(lintBuf.String())
+			return 0, errors.New(lintBuf.String())
 		} else if len(lintResults.Warnings) == 0 && f.Format != "json" {
-			fmt.Println("Check complete, no warnings found.")
+			fmt.Fprintln(w, "Check complete, no warnings found.")
 		}
 	default:
 		if dt, ok := res["result.json"]; ok && f.Format == "json" {
-			fmt.Println(dt)
+			fmt.Fprintln(w, dt)
 		} else if dt, ok := res["result.txt"]; ok {
-			fmt.Print(dt)
+			fmt.Fprint(w, dt)
 		} else {
-			log.Printf("%s %+v", f, res)
+			fmt.Fprintf(w, "%s %+v\n", f, res)
 		}
 	}
 	if v, ok := res["result.statuscode"]; !f.IgnoreStatus && ok {
 		if n, err := strconv.Atoi(v); err == nil && n != 0 {
-			os.Exit(n)
+			return n, nil
 		}
 	}
-	return nil
+	return 0, nil
 }
 
 type printFunc func([]byte, io.Writer) error
 
-func printValue(printer printFunc, version string, format string, res map[string]string) error {
+func printValue(w io.Writer, printer printFunc, version string, format string, res map[string]string) error {
 	if format == "json" {
-		fmt.Fprintln(os.Stdout, res["result.json"])
+		fmt.Fprintln(w, res["result.json"])
 		return nil
 	}
 
 	if res["version"] != "" && versions.LessThan(version, res["version"]) && res["result.txt"] != "" {
 		// structure is too new and we don't know how to print it
-		fmt.Fprint(os.Stdout, res["result.txt"])
+		fmt.Fprint(w, res["result.txt"])
 		return nil
 	}
-	return printer([]byte(res["result.json"]), os.Stdout)
+	return printer([]byte(res["result.json"]), w)
 }
 
 type invokeConfig struct {
@@ -1042,7 +1042,7 @@ func maybeJSONArray(v string) []string {
 	return []string{v}
 }
 
-func callAlias(options *buildOptions, value string) cobrautil.BoolFuncValue {
+func callAlias(target *string, value string) cobrautil.BoolFuncValue {
 	return func(s string) error {
 		v, err := strconv.ParseBool(s)
 		if err != nil {
@@ -1050,7 +1050,7 @@ func callAlias(options *buildOptions, value string) cobrautil.BoolFuncValue {
 		}
 
 		if v {
-			options.printFunc = value
+			*target = value
 		}
 		return nil
 	}

docs/reference/buildx_bake.md

@@ -16,6 +16,8 @@ Build from a file
 | Name                                | Type          | Default | Description                                                                                         |
 |:------------------------------------|:--------------|:--------|:----------------------------------------------------------------------------------------------------|
 | [`--builder`](#builder)             | `string`      |         | Override the configured builder instance                                                            |
+| `--call`                            | `string`      | `build` | Set method for evaluating build (`check`, `outline`, `targets`)                                     |
+| `--check`                           | `bool`        |         | Shorthand for `--call=check`                                                                        |
 | [`-f`](#file), [`--file`](#file)    | `stringArray` |         | Build definition file                                                                               |
 | `--load`                            | `bool`        |         | Shorthand for `--set=*.output=type=docker`                                                          |
 | [`--metadata-file`](#metadata-file) | `string`      |         | Write build result metadata to a file                                                               |

tests/bake.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/containerd/continuity/fs/fstest"
@@ -48,6 +49,10 @@ var bakeTests = []func(t *testing.T, sb integration.Sandbox){
 	testBakeMetadataWarningsDedup,
 	testBakeMultiExporters,
 	testBakeLoadPush,
+	testListTargets,
+	testListVariables,
+	testBakeCallCheck,
+	testBakeCallCheckFlag,
 }
 
 func testBakeLocal(t *testing.T, sb integration.Sandbox) {
@@ -951,3 +956,163 @@ target "default" {
 
 	// TODO: test metadata file when supported by multi exporters https://github.com/docker/buildx/issues/2181
 }
+
+func testListTargets(t *testing.T, sb integration.Sandbox) {
+	bakefile := []byte(`
+target "foo" {
+	description = "This builds foo"
+}
+target "abc" {
+}
+`)
+	dir := tmpdir(
+		t,
+		fstest.CreateFile("docker-bake.hcl", bakefile, 0600),
+	)
+
+	out, err := bakeCmd(
+		sb,
+		withDir(dir),
+		withArgs("--list-targets"),
+	)
+	require.NoError(t, err, out)
+
+	require.Equal(t, "TARGET\tDESCRIPTION\nabc\t\nfoo\tThis builds foo", strings.TrimSpace(out))
+}
+
+func testListVariables(t *testing.T, sb integration.Sandbox) {
+	bakefile := []byte(`
+variable "foo" {
+	default = "bar"
+	description = "This is foo"
+}
+variable "abc" {
+	default = null
+}
+variable "def" {
+}
+target "default" {
+}
+`)
+	dir := tmpdir(
+		t,
+		fstest.CreateFile("docker-bake.hcl", bakefile, 0600),
+	)
+
+	out, err := bakeCmd(
+		sb,
+		withDir(dir),
+		withArgs("--list-variables"),
+	)
+	require.NoError(t, err, out)
+
+	require.Equal(t, "VARIABLE\tVALUE\tDESCRIPTION\nabc\t\t<null>\t\ndef\t\t\t\nfoo\t\tbar\tThis is foo", strings.TrimSpace(out))
+}
+
+func testBakeCallCheck(t *testing.T, sb integration.Sandbox) {
+	dockerfile := []byte(`
+FROM scratch
+COPy foo /foo
+	`)
+	bakefile := []byte(`
+target "validate" {
+	call = "check"
+}
+`)
+	dir := tmpdir(
+		t,
+		fstest.CreateFile("docker-bake.hcl", bakefile, 0600),
+		fstest.CreateFile("Dockerfile", dockerfile, 0600),
+	)
+
+	out, err := bakeCmd(
+		sb,
+		withDir(dir),
+		withArgs("validate"),
+	)
+	require.Error(t, err, out)
+
+	require.Contains(t, out, "validate")
+	require.Contains(t, out, "ConsistentInstructionCasing")
+}
+
+func testBakeCallCheckFlag(t *testing.T, sb integration.Sandbox) {
+	dockerfile := []byte(`
+FROM scratch
+COPy foo /foo
+	`)
+	dockerfile2 := []byte(`
+FROM scratch
+COPY foo$BAR /foo
+		`)
+	bakefile := []byte(`
+target "build" {
+	dockerfile = "a.Dockerfile"
+}
+
+target "another" {
+	dockerfile = "b.Dockerfile"
+}
+`)
+	dir := tmpdir(
+		t,
+		fstest.CreateFile("docker-bake.hcl", bakefile, 0600),
+		fstest.CreateFile("a.Dockerfile", dockerfile, 0600),
+		fstest.CreateFile("b.Dockerfile", dockerfile2, 0600),
+	)
+
+	out, err := bakeCmd(
+		sb,
+		withDir(dir),
+		withArgs("build", "another", "--check"),
+	)
+	require.Error(t, err, out)
+
+	require.Contains(t, out, "build")
+	require.Contains(t, out, "ConsistentInstructionCasing")
+
+	require.Contains(t, out, "another")
+	require.Contains(t, out, "UndefinedVar")
+
+	out, err = bakeCmd(
+		sb,
+		withDir(dir),
+		withArgs("build", "another", "--call", "check,format=json"),
+	)
+	require.Error(t, err, out)
+
+	var res map[string]any
+	err = json.Unmarshal([]byte(out), &res)
+	require.NoError(t, err, out)
+
+	targets, ok := res["target"].(map[string]any)
+	require.True(t, ok)
+
+	build, ok := targets["build"].(map[string]any)
+	require.True(t, ok)
+
+	_, ok = build["build"]
+	require.True(t, ok)
+
+	check, ok := build["check"].(map[string]any)
+	require.True(t, ok)
+
+	warnings, ok := check["warnings"].([]any)
+	require.True(t, ok)
+
+	require.Len(t, warnings, 1)
+
+	another, ok := targets["another"].(map[string]any)
+	require.True(t, ok)
+
+	_, ok = another["build"]
+	require.True(t, ok)
+
+	check, ok = another["check"].(map[string]any)
+	require.True(t, ok)
+
+	warnings, ok = check["warnings"].([]any)
+	require.True(t, ok)
+
+	require.Len(t, warnings, 1)
+}

util/progress/printer.go

@@ -22,6 +22,7 @@ type Printer struct {
 	ready     chan struct{}
 	done      chan struct{}
 	paused    chan struct{}
+	closeOnce sync.Once
 
 	err          error
 	warnings     []client.VertexWarning
@@ -36,8 +37,10 @@ type Printer struct {
 }
 
 func (p *Printer) Wait() error {
+	p.closeOnce.Do(func() {
 		close(p.status)
 		<-p.done
+	})
 	return p.err
 }