Set empty TARGETVARIANT and BUILDVARIANT

Docker does not set these values for ARM64.
This fixes the TestConformance/multistage-builtin-args and TestConformance/builtins tests on ARM64.

Signed-off-by: Jan Rodák <[email protected]>

Author: Honny1

imagebuildah/build.go

@@ -427,12 +427,9 @@ func buildDockerfilesOnce(ctx context.Context, store storage.Store, logger *logr
 		// fill them in using values for the default platform
 		defaultPlatform := platforms.DefaultSpec()
 		builtinArgDefaults["TARGETOS"] = defaultPlatform.OS
-		builtinArgDefaults["TARGETVARIANT"] = defaultPlatform.Variant
+		builtinArgDefaults["TARGETVARIANT"] = ""
 		builtinArgDefaults["TARGETARCH"] = defaultPlatform.Architecture
 		builtinArgDefaults["TARGETPLATFORM"] = defaultPlatform.OS + "/" + defaultPlatform.Architecture
-		if defaultPlatform.Variant != "" {
-			builtinArgDefaults["TARGETPLATFORM"] += "/" + defaultPlatform.Variant
-		}
 	}
 	delete(options.Args, "TARGETPLATFORM")
 
@@ -453,6 +450,13 @@ func buildDockerfilesOnce(ctx context.Context, store storage.Store, logger *logr
 	for k, v := range builtinArgDefaults {
 		b.BuiltinArgDefaults[k] = v
 	}
+
+	buildVariant := b.BuiltinArgDefaults["BUILDVARIANT"]
+	buildPlatform := b.BuiltinArgDefaults["BUILDPLATFORM"]
+	cleanedBuildPlatform, _ := strings.CutSuffix(buildPlatform, "/"+buildVariant)
+	b.BuiltinArgDefaults["BUILDPLATFORM"] = cleanedBuildPlatform
+	b.BuiltinArgDefaults["BUILDVARIANT"] = ""
+
 	defaultContainerConfig, err := config.Default()
 	if err != nil {
 		return "", nil, fmt.Errorf("failed to get container config: %w", err)

tests/bud.bats

@@ -290,7 +290,8 @@ _EOF
          "With explicit --platform, buildah should warn about pulling difference in platform"
   assert "$output" =~ "TARGETOS=linux" " --platform TARGETOS set correctly"
   assert "$output" =~ "TARGETARCH=amd64" " --platform TARGETARCH set correctly"
-  assert "$output" =~ "TARGETVARIANT=" " --platform TARGETVARIANT set correctly"
+  # By default, BUILDVARIANT/TARGETVARIANT should be empty.
+  assert "$output" =~ "TARGETVARIANT=\s" " --platform TARGETVARIANT set correctly"
   assert "$output" =~ "TARGETPLATFORM=linux/amd64/v2" " --platform TARGETPLATFORM set correctly"
 
   # Likewise with individual args
@@ -300,23 +301,26 @@ _EOF
          "With explicit --variant, buildah should warn about pulling difference in platform"
   assert "$output" =~ "TARGETOS=linux" "--os --arch --variant TARGETOS set correctly"
   assert "$output" =~ "TARGETARCH=amd64" "--os --arch --variant TARGETARCH set correctly"
-  assert "$output" =~ "TARGETVARIANT=" "--os --arch --variant TARGETVARIANT set correctly"
+  # By default, BUILDVARIANT/TARGETVARIANT should be empty.
+  assert "$output" =~ "TARGETVARIANT=\s" "--os --arch --variant TARGETVARIANT set correctly"
   assert "$output" =~ "TARGETPLATFORM=linux/amd64" "--os --arch --variant TARGETPLATFORM set correctly"
 
   run_buildah build $WITH_POLICY_JSON --os linux -t source -f $containerfile
   assert "$output" !~ "WARNING" \
          "With explicit --os (but no arch/variant), buildah should not warn about TARGETOS"
   assert "$output" =~ "TARGETOS=linux" "--os TARGETOS set correctly"
   assert "$output" =~ "TARGETARCH=${ARCH}" "--os TARGETARCH set correctly"
-  assert "$output" =~ "TARGETVARIANT=" "--os TARGETVARIANT set correctly"
+  # By default, BUILDVARIANT/TARGETVARIANT should be empty.
+  assert "$output" =~ "TARGETVARIANT=\s" "--os TARGETVARIANT set correctly"
   assert "$output" =~ "TARGETPLATFORM=linux/${ARCH}" "--os TARGETPLATFORM set correctly"
 
   run_buildah build $WITH_POLICY_JSON --arch amd64 -t source -f $containerfile
   assert "$output" !~ "WARNING" \
          "With explicit --os (but no arch/variant), buildah should not warn about TARGETOS"
   assert "$output" =~ "TARGETOS=linux" "--arch TARGETOS set correctly"
   assert "$output" =~ "TARGETARCH=amd64" "--arch TARGETARCH set correctly"
-  assert "$output" =~ "TARGETVARIANT=" "--arch TARGETVARIANT set correctly"
+  # By default, BUILDVARIANT/TARGETVARIANT should be empty.
+  assert "$output" =~ "TARGETVARIANT=\s" "--arch TARGETVARIANT set correctly"
   assert "$output" =~ "TARGETPLATFORM=linux/amd64" "--arch TARGETPLATFORM set correctly"
 
   for option in "--arch=arm64" "--os=windows" "--variant=v2"; do

tests/conformance/conformance_test.go

@@ -3321,7 +3321,7 @@ var internalTestCases = []testCase{
 	},
 
 	{
-		name:              "multistage-builtin-args",
+		name:              "multistage-builtin-args", // By default, BUILDVARIANT/TARGETVARIANT should be empty.
 		dockerfile:        "Dockerfile.margs",
 		dockerUseBuildKit: true,
 	},