Merge pull request #3698 from Luap99/os-arch

Fix platform handling for empty os/arch values

imagebuildah/build.go

@@ -216,8 +216,12 @@ func BuildDockerfiles(ctx context.Context, store storage.Store, options define.B
 			Architecture: platform.Arch,
 			Variant:      platform.Variant,
 		})
-		if platformSpec.OS != "" && platformSpec.Architecture != "" {
+		// platforms.Normalize converts an empty os value to GOOS
+		// so we have to check the original value here to not overwrite the default for no reason
+		if platform.OS != "" {
 			platformContext.OSChoice = platformSpec.OS
+		}
+		if platform.Arch != "" {
 			platformContext.ArchitectureChoice = platformSpec.Architecture
 			platformContext.VariantChoice = platformSpec.Variant
 		}

tests/bud.bats

@@ -2429,6 +2429,30 @@ EOM
   expect_output arm
 }
 
+@test "bud with custom platform and empty os or arch" {
+  run_buildah build --signature-policy ${TESTSDIR}/policy.json \
+    -f ${TESTSDIR}/bud/from-scratch/Containerfile \
+    -t platform-test \
+    --platform=windows/
+
+  run_buildah inspect --format "{{ .Docker.OS }}" platform-test
+  expect_output windows
+
+  run_buildah inspect --format "{{ .OCIv1.OS }}" platform-test
+  expect_output windows
+
+  run_buildah build --signature-policy ${TESTSDIR}/policy.json \
+    -f ${TESTSDIR}/bud/from-scratch/Containerfile \
+    -t platform-test2 \
+    --platform=/arm
+
+  run_buildah inspect --format "{{ .Docker.Architecture }}" platform-test2
+  expect_output arm
+
+  run_buildah inspect --format "{{ .OCIv1.Architecture }}" platform-test2
+  expect_output arm
+}
+
 @test "bud Add with linked tarball" {
   _prefetch alpine
   run_buildah build --signature-policy ${TESTSDIR}/policy.json -f ${TESTSDIR}/bud/symlink/Containerfile.add-tar-with-link -t testctr ${TESTSDIR}/bud/symlink