Allow setting XCODE_VERSION_OVERRIDE to a DEVELOPER_DIR path

Support for this was added in Bazel commit
d2e8c82570c63e9a0c6ef369ef458a86f587e819. It can be used to force the
use of a specific version of Xcode.

Author: EdSchouten

pkg/runner/apple_xcode_resolving_runner.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 
 	runner_pb "github.com/buildbarn/bb-remote-execution/pkg/proto/runner"
+	"github.com/buildbarn/bb-storage/pkg/filesystem/path"
 	"github.com/buildbarn/bb-storage/pkg/util"
 
 	"google.golang.org/grpc/codes"
@@ -134,7 +135,14 @@ func (r *appleXcodeResolvingRunner) Run(ctx context.Context, oldRequest *runner_
 
 	developerDir, ok := r.developerDirectories[xcodeVersion]
 	if !ok {
-		return nil, status.Errorf(codes.FailedPrecondition, "Attempted to use Xcode installation with version %#v, while only %s are supported", xcodeVersion, r.supportedVersions)
+		// Bazel 8.3 and later also allow XCODE_VERSION_OVERRIDE
+		// to be set to a DEVELOPER_DIR path. This can be used
+		// to force the use of a specific copy of Xcode.
+		developerDirBuilder, scopeWalker := path.EmptyBuilder.Join(path.NewAbsoluteScopeWalker(path.VoidComponentWalker))
+		if err := path.Resolve(path.UNIXFormat.NewParser(xcodeVersion), scopeWalker); err != nil {
+			return nil, status.Errorf(codes.FailedPrecondition, "Attempted to use Xcode installation with version %#v, while only %s are supported", xcodeVersion, r.supportedVersions)
+		}
+		developerDir = developerDirBuilder.GetUNIXString()
 	}
 
 	var newRequest runner_pb.RunRequest

pkg/runner/apple_xcode_resolving_runner_test.go

@@ -164,4 +164,31 @@ func TestAppleXcodeResolvingRunner(t *testing.T) {
 		require.NoError(t, err)
 		testutil.RequireEqualProto(t, response, observedResponse)
 	})
+
+	t.Run("XcodeVersionOverrideIsDeveloperDir", func(t *testing.T) {
+		// Bazel 8.3 and later also allow XCODE_VERSION_OVERRIDE
+		// to be set to a DEVELOPER_DIR path. This can be used
+		// to force the use of a specific copy of Xcode.
+		sdkRootResolver.EXPECT().Call(ctx, "/Applications/Xcode12.app/Contents/Developer", "macosx").
+			Return("/Applications/Xcode12.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.0.sdk", nil)
+		baseRunner.EXPECT().Run(ctx, testutil.EqProto(t, &runner_pb.RunRequest{
+			Arguments: []string{"cc", "-o", "hello.o", "hello.c"},
+			EnvironmentVariables: map[string]string{
+				"APPLE_SDK_PLATFORM":     "MacOSX",
+				"DEVELOPER_DIR":          "/Applications/Xcode12.app/Contents/Developer",
+				"SDKROOT":                "/Applications/Xcode12.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.0.sdk",
+				"XCODE_VERSION_OVERRIDE": "/Applications/Xcode12.app/Contents/Developer",
+			},
+		})).Return(response, nil)
+
+		observedResponse, err := runner.Run(ctx, &runner_pb.RunRequest{
+			Arguments: []string{"cc", "-o", "hello.o", "hello.c"},
+			EnvironmentVariables: map[string]string{
+				"APPLE_SDK_PLATFORM":     "MacOSX",
+				"XCODE_VERSION_OVERRIDE": "/Applications/Xcode12.app/Contents/Developer",
+			},
+		})
+		require.NoError(t, err)
+		testutil.RequireEqualProto(t, response, observedResponse)
+	})
 }