Setting --arch should set the TARGETARCH build arg

imagebuildah/build.go

@@ -11,6 +11,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"runtime"
 	"strconv"
 	"strings"
 	"sync"
@@ -221,6 +222,9 @@ func BuildDockerfiles(ctx context.Context, store storage.Store, options define.B
 	systemContext := options.SystemContext
 	for _, platform := range options.Platforms {
 		platformContext := *systemContext
+		if platform.OS == "" {
+			platform.OS = runtime.GOOS
+		}
 		platformSpec := internalUtil.NormalizePlatform(v1.Platform{
 			OS:           platform.OS,
 			Architecture: platform.Arch,

tests/bud.bats

@@ -243,26 +243,48 @@ _EOF
   assert "${checkvars[*]}" != "" \
          "INTERNAL ERROR! No 'ARG xxx' lines in $containerfile!"
 
+  ARCH=$(go env GOARCH)
   # With explicit and full --platform, buildah should not warn.
   run_buildah build $WITH_POLICY_JSON --platform linux/amd64/v2 \
               -t source -f $containerfile
-  assert "$output" !~ "missing .* build argument" \
-         "With explicit --platform, buildah should not warn"
+  assert "$output" =~ "image platform \(linux/amd64\) does not match the expected platform" \
+         "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 "$output" =~ "TARGETVARIANT=" " --platform TARGETVARIANT set correctly"
+  assert "$output" =~ "TARGETPLATFORM=linux/amd64/v2" " --platform TARGETPLATFORM set correctly"
 
   # Likewise with individual args
   run_buildah build $WITH_POLICY_JSON --os linux --arch amd64 --variant v2 \
               -t source -f $containerfile
-  assert "$output" !~ "missing .* build argument" \
-         "With explicit --os + --arch + --variant, buildah should not warn"
-
-  # FIXME FIXME FIXME: #4319: with --os only, buildah should not warn about OS
-  if false; then
-      run_buildah build $WITH_POLICY_JSON --os linux \
-                  -t source -f $containerfile
-      assert "$output" !~ "missing.*TARGETOS" \
-             "With explicit --os (but no arch/variant), buildah should not warn about TARGETOS"
-      # FIXME: add --arch test too, and maybe make this cleaner
-  fi
+  assert "$output" =~ "image platform \(linux/amd64\) does not match the expected platform" \
+         "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 "$output" =~ "TARGETVARIANT=" "--os --arch --variant TARGETVARIANT set correctly"
+  assert "$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"
+  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 "$output" =~ "TARGETVARIANT=" "--arch TARGETVARIANT set correctly"
+  assert "$output" =~ "TARGETPLATFORM=linux/amd64" "--arch TARGETPLATFORM set correctly"
+
+  for option in "--arch=arm64" "--os=windows" "--variant=v2"; do
+    run_buildah 125 build $WITH_POLICY_JSON --platform linux/amd64 ${option} \
+                -t source -f $containerfile
+    assert "$output" =~ "Error: building system context: invalid --platform may not be used with --os, --arch, or --variant" "can't use --platform and one of --os, --arch or --variant together"
+  done
 }
 
 @test "build-conflicting-isolation-chroot-and-network" {
@@ -5729,9 +5751,9 @@ _EOF
 @test "bud with --pull-always" {
   _prefetch docker.io/library/alpine
   run_buildah build --pull-always $WITH_POLICY_JSON -t testpull $BUDFILES/containerfile
-  expect_output --from="${lines[1]}" "Trying to pull docker.io/library/alpine:latest..."
+  expect_output --substring "Trying to pull docker.io/library/alpine:latest..."
   run_buildah build --pull=always $WITH_POLICY_JSON -t testpull $BUDFILES/containerfile
-  expect_output --from="${lines[1]}" "Trying to pull docker.io/library/alpine:latest..."
+  expect_output --substring "Trying to pull docker.io/library/alpine:latest..."
 }
 
 @test "bud with --memory and --memory-swap" {

tests/bud/platform-sets-args/Containerfile

@@ -4,3 +4,7 @@ ARG TARGETOS
 ARG TARGETPLATFORM
 ARG TARGETVARIANT
 ENV nothing="multiarch-safe statement that will result in a built image"
+run echo TARGETARCH=${TARGETARCH}
+run echo TARGETOS=${TARGETOS}
+run echo TARGETPLATFORM=${TARGETPLATFORM}
+run echo TARGETVARIANT=${TARGETVARANT}

tests/conformance/conformance_test.go

@@ -3566,11 +3566,11 @@ func TestCommit(t *testing.T) {
 				derivedBuilder, err := buildah.NewBuilder(ctx, store, buildah.BuilderOptions{
 					FromImage: buildahID,
 				})
+				require.NoErrorf(t, err, "creating the derived container with buildah")
 				defer func(builder *buildah.Builder) {
 					err := builder.Delete()
 					assert.NoErrorf(t, err, "removing the derived container")
 				}(derivedBuilder)
-				require.NoErrorf(t, err, "creating the derived container with buildah")
 				var overrideConfig *manifest.Schema2Config
 				if test.derivedConfig != nil {
 					overrideConfig = config.Schema2ConfigFromGoDockerclientConfig(test.derivedConfig)