feat: support pre-defined build args of multi-platform build arguments

integration/dockerfiles/Dockerfile_test_pre_defined_build_args

@@ -0,0 +1,46 @@
+# ingegration test for pre-defined build args; see pkg/dockerfile/buildargs.go
+FROM alpine:3 AS builder
+ARG BUILDPLATFORM
+ARG BUILDOS
+ARG BUILDARCH
+ARG BUILDVARIANT
+ARG TARGETPLATFORM
+ARG TARGETOS
+ARG TARGETARCH
+ARG TARGETVARIANT
+ARG TARGETSTAGE
+RUN echo "BUILDPLATFORM: ${BUILDPLATFORM}" && \
+    echo "BUILDOS: ${BUILDOS}" && \
+    echo "BUILDARCH: ${BUILDARCH}" && \
+    echo "BUILDVARIANT: ${BUILDVARIANT}" && \
+    echo "TARGETPLATFORM: ${TARGETPLATFORM}" && \
+    echo "TARGETOS: ${TARGETOS}" && \
+    echo "TARGETARCH: ${TARGETARCH}" && \
+    echo "TARGETVARIANT: ${TARGETVARIANT}" && \
+    echo "TARGETSTAGE: ${TARGETSTAGE}"
+RUN uname -a
+COPY foo /app/foo
+RUN echo 'add line' >> /app/foo
+
+FROM alpine:3
+COPY --from=builder /app/foo /app/foo
+ARG BUILDPLATFORM
+ARG BUILDOS
+ARG BUILDARCH
+ARG BUILDVARIANT
+ARG TARGETPLATFORM
+ARG TARGETOS
+ARG TARGETARCH
+ARG TARGETVARIANT
+ARG TARGETSTAGE
+RUN echo "BUILDPLATFORM: ${BUILDPLATFORM}" && \
+    echo "BUILDOS: ${BUILDOS}" && \
+    echo "BUILDARCH: ${BUILDARCH}" && \
+    echo "BUILDVARIANT: ${BUILDVARIANT}" && \
+    echo "TARGETPLATFORM: ${TARGETPLATFORM}" && \
+    echo "TARGETOS: ${TARGETOS}" && \
+    echo "TARGETARCH: ${TARGETARCH}" && \
+    echo "TARGETVARIANT: ${TARGETVARIANT}" && \
+    echo "TARGETSTAGE: ${TARGETSTAGE}"
+RUN uname -a
+RUN cat /app/foo

pkg/dockerfile/buildargs.go

@@ -17,12 +17,21 @@ limitations under the License.
 package dockerfile
 
 import (
+	"fmt"
 	"strings"
+	"sync"
 
+	"github.com/GoogleContainerTools/kaniko/pkg/config"
+	"github.com/containerd/platforms"
 	d "github.com/docker/docker/builder/dockerfile"
+	containerregistryV1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/moby/buildkit/frontend/dockerfile/instructions"
+	"github.com/sirupsen/logrus"
 )
 
+var defaultArgsOnce sync.Once
+var defaultArgs []string
+
 type BuildArgs struct {
 	d.BuildArgs
 }
@@ -68,3 +77,45 @@ func (b *BuildArgs) AddMetaArgs(metaArgs []instructions.ArgCommand) {
 		}
 	}
 }
+
+// DefaultArgs get default args.
+// include pre-defined build args: TARGETOS, TARGETARCH, BUILDPLATFORM, TARGETPLATFORM ...
+func DefaultArgs(opt config.KanikoOptions) []string {
+	defaultArgsOnce.Do(func() {
+		// build info
+		buildPlatform := platforms.Format(platforms.Normalize(platforms.DefaultSpec()))
+		buildPlatformSpec, err := containerregistryV1.ParsePlatform(buildPlatform)
+		if err != nil {
+			logrus.Fatalf("Parse build platform %q: %v", buildPlatform, err)
+		}
+
+		// target info
+		var targetPlatform string
+		if opt.CustomPlatform != "" {
+			targetPlatform = opt.CustomPlatform
+		} else {
+			targetPlatform = buildPlatform
+		}
+		targetPlatformSpec, err := containerregistryV1.ParsePlatform(opt.CustomPlatform)
+		if err != nil {
+			logrus.Fatalf("Invalid platform %q: %v", opt.CustomPlatform, err)
+		}
+
+		// pre-defined build args
+		defaultArgs = []string{
+			fmt.Sprintf("%s=%s", "BUILDPLATFORM", buildPlatform),
+			fmt.Sprintf("%s=%s", "BUILDOS", buildPlatformSpec.OS),
+			fmt.Sprintf("%s=%s", "BUILDOSVERSION", buildPlatformSpec.OSVersion),
+			fmt.Sprintf("%s=%s", "BUILDARCH", buildPlatformSpec.Architecture),
+			fmt.Sprintf("%s=%s", "BUILDVARIANT", buildPlatformSpec.Variant),
+			fmt.Sprintf("%s=%s", "TARGETPLATFORM", targetPlatform),
+			fmt.Sprintf("%s=%s", "TARGETOS", targetPlatformSpec.OS),
+			fmt.Sprintf("%s=%s", "TARGETOSVERSION", targetPlatformSpec.OSVersion),
+			fmt.Sprintf("%s=%s", "TARGETARCH", targetPlatformSpec.Architecture),
+			fmt.Sprintf("%s=%s", "TARGETVARIANT", targetPlatformSpec.Variant),
+			fmt.Sprintf("%s=%s", "TARGETSTAGE", opt.Target),
+		}
+		logrus.Infof("init default args: %s", defaultArgs)
+	})
+	return defaultArgs
+}

pkg/executor/build.go

@@ -146,7 +146,9 @@ func newStageBuilder(args *dockerfile.BuildArgs, opts *config.KanikoOptions, sta
 	if args != nil {
 		s.args = args.Clone()
 	} else {
-		s.args = dockerfile.NewBuildArgs(s.opts.BuildArgs)
+		defaultArgs := dockerfile.DefaultArgs(*opts)
+		mergedArgs := append(defaultArgs, s.opts.BuildArgs...)
+		s.args = dockerfile.NewBuildArgs(mergedArgs)
 	}
 	s.args.AddMetaArgs(s.stage.MetaArgs)
 	return s, nil