Add automatic platform args in the global scope

Signed-off-by: Daniel Black <[email protected]>

dispatchers.go

@@ -21,12 +21,34 @@ import (
 
 	"github.com/openshift/imagebuilder/signal"
 	"github.com/openshift/imagebuilder/strslice"
+	"github.com/containerd/containerd/platforms"
 )
 
 var (
 	obRgex = regexp.MustCompile(`(?i)^\s*ONBUILD\s*`)
 )
 
+var localspec = platforms.DefaultSpec()
+
+// https://docs.docker.com/engine/reference/builder/#automatic-platform-args-in-the-global-scope
+var builtinBuildArgs = map[string]string{
+	"TARGETPLATFORM": localspec.OS + "/" + localspec.Architecture,
+	"TARGETOS":       localspec.OS,
+	"TARGETARCH":     localspec.Architecture,
+	"TARGETVARIANT":  localspec.Variant,
+	"BUILDPLATFORM":  localspec.OS + "/" + localspec.Architecture,
+	"BUILDOS":        localspec.OS,
+	"BUILDARCH":      localspec.Architecture,
+	"BUILDVARIANT":   localspec.Variant,
+}
+
+func init() {
+	if localspec.Variant != "" {
+		builtinBuildArgs["TARGETPLATFORM"] = builtinBuildArgs["TARGETPLATFORM"] + "/" + localspec.Variant
+		builtinBuildArgs["BUILDPLATFORM"] = builtinBuildArgs["BUILDPLATFORM"] + "/" + localspec.Variant
+	}
+}
+
 // ENV foo bar
 //
 // Sets the environment variable foo to bar, also makes interpolation
@@ -516,6 +538,9 @@ func healthcheck(b *Builder, args []string, attributes map[string]bool, flagArgs
 	return nil
 }
 
+
+var targetArgs = []string {"TARGETOS", "TARGETARCH", "TARGETVARIANT"}
+
 // ARG name[=value]
 //
 // Adds the variable foo to the trusted list of variables that can be passed
@@ -543,6 +568,26 @@ func arg(b *Builder, args []string, attributes map[string]bool, flagArgs []strin
 		name = parts[0]
 		value = parts[1]
 		hasDefault = true
+		if name == "TARGETPLATFORM" {
+			p, err := platforms.Parse(value)
+			if err != nil {
+				return fmt.Errorf("error parsing TARGETPLATFORM argument")
+			}
+			for _, val := range targetArgs {
+				b.AllowedArgs[val] = true
+			}
+			b.Args["TARGETPLATFORM"] = p.OS + "/" + p.Architecture
+			b.Args["TARGETOS"] = p.OS
+			b.Args["TARGETARCH"] = p.Architecture
+			b.Args["TARGETVARIANT"] = p.Variant
+			if p.Variant != "" {
+				b.Args["TARGETPLATFORM"] = b.Args["TARGETPLATFORM"] + "/" + p.Variant
+			}
+		}
+	} else if val, ok := builtinBuildArgs[arg]; ok {
+		name = arg
+		value = val
+		hasDefault = true
 	} else {
 		name = arg
 		hasDefault = false

dispatchers_test.go

@@ -3,10 +3,64 @@ package imagebuilder
 import (
 	"reflect"
 	"testing"
+	"sort"
+	"errors"
+	"github.com/containerd/containerd/platforms"
 
 	docker "github.com/fsouza/go-dockerclient"
 )
 
+func TestDispatchArgDefaultBuiltins(t *testing.T) {
+	mybuilder := *NewBuilder(make(map[string]string))
+	args := []string{"TARGETPLATFORM"}
+	if err := arg(&mybuilder, args, nil, nil, ""); err != nil {
+		t.Errorf("arg error: %v", err)
+	}
+	args = []string{"BUILDARCH"}
+	if err := arg(&mybuilder, args, nil, nil, ""); err != nil {
+		t.Errorf("arg(2) error: %v", err)
+	}
+	localspec := platforms.DefaultSpec()
+	expectedArgs := []string {
+		"BUILDARCH=" + localspec.Architecture,
+		"TARGETPLATFORM=" + localspec.OS + "/" + localspec.Architecture,
+	}
+	got := mybuilder.Arguments()
+	sort.Strings(got)
+	if !reflect.DeepEqual(got, expectedArgs) {
+		t.Errorf("Expected %v, got %v\n", expectedArgs, got)
+	}
+}
+
+func TestDispatchArgTargetPlatform(t *testing.T) {
+	mybuilder := *NewBuilder(make(map[string]string))
+	args := []string{"TARGETPLATFORM=linux/arm/v7"}
+	if err := arg(&mybuilder, args, nil, nil, ""); err != nil {
+		t.Errorf("arg error: %v", err)
+	}
+	expectedArgs := []string {
+		"TARGETARCH=arm",
+		"TARGETOS=linux",
+		"TARGETPLATFORM=linux/arm/v7",
+		"TARGETVARIANT=v7",
+	}
+	got := mybuilder.Arguments()
+	sort.Strings(got)
+	if !reflect.DeepEqual(got, expectedArgs) {
+		t.Errorf("Expected %v, got %v\n", expectedArgs, got)
+	}
+}
+
+func TestDispatchArgTargetPlatformBad(t *testing.T) {
+	mybuilder := *NewBuilder(make(map[string]string))
+	args := []string{"TARGETPLATFORM=bozo"}
+	err := arg(&mybuilder, args, nil, nil, "")
+	expectedErr := errors.New("error parsing TARGETPLATFORM argument")
+	if !reflect.DeepEqual(err, expectedErr) {
+		t.Errorf("Expected %v, got %v\n", expectedErr, err)
+	}
+}
+
 func TestDispatchCopy(t *testing.T) {
 	mybuilder := Builder{
 		RunConfig: docker.Config{