Preserve explicit directory markers with octet-stream MIME (#8726)

* Preserve octet-stream MIME on explicit directory markers

* Run empty directory marker regression in CI

* Run S3 Spark workflow for filer changes

weed/filer/filerstore_wrapper.go

@@ -128,9 +128,7 @@ func (fsw *FilerStoreWrapper) InsertEntry(ctx context.Context, entry *Entry) err
 	}()
 
 	filer_pb.BeforeEntrySerialization(entry.GetChunks())
-	if entry.Mime == "application/octet-stream" {
-		entry.Mime = ""
-	}
+	normalizeEntryMimeForStore(entry)
 
 	if err := fsw.handleUpdateToHardLinks(ctx, entry); err != nil {
 		return err
@@ -150,9 +148,7 @@ func (fsw *FilerStoreWrapper) UpdateEntry(ctx context.Context, entry *Entry) err
 	}()
 
 	filer_pb.BeforeEntrySerialization(entry.GetChunks())
-	if entry.Mime == "application/octet-stream" {
-		entry.Mime = ""
-	}
+	normalizeEntryMimeForStore(entry)
 
 	if err := fsw.handleUpdateToHardLinks(ctx, entry); err != nil {
 		return err
@@ -162,6 +158,15 @@ func (fsw *FilerStoreWrapper) UpdateEntry(ctx context.Context, entry *Entry) err
 	return actualStore.UpdateEntry(ctx, entry)
 }
 
+func normalizeEntryMimeForStore(entry *Entry) {
+	if entry == nil {
+		return
+	}
+	if !entry.IsDirectory() && entry.Mime == "application/octet-stream" {
+		entry.Mime = ""
+	}
+}
+
 func (fsw *FilerStoreWrapper) FindEntry(ctx context.Context, fp util.FullPath) (entry *Entry, err error) {
 	ctx = context.WithoutCancel(ctx)
 	actualStore := fsw.getActualStore(fp)

weed/filer/filerstore_wrapper_test.go

@@ -0,0 +1,71 @@
+package filer
+
+import (
+	"context"
+	"os"
+	"testing"
+
+	"github.com/seaweedfs/seaweedfs/weed/util"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestFilerStoreWrapperMimeNormalization(t *testing.T) {
+	tests := []struct {
+		name     string
+		mode     os.FileMode
+		wantMime string
+	}{
+		{
+			name:     "files strip octet-stream",
+			mode:     0o660,
+			wantMime: "",
+		},
+		{
+			name:     "directories keep octet-stream",
+			mode:     os.ModeDir | 0o770,
+			wantMime: "application/octet-stream",
+		},
+	}
+
+	operations := []struct {
+		name string
+		run  func(*FilerStoreWrapper, context.Context, *Entry) error
+	}{
+		{
+			name: "insert",
+			run: func(fsw *FilerStoreWrapper, ctx context.Context, entry *Entry) error {
+				return fsw.InsertEntry(ctx, entry)
+			},
+		},
+		{
+			name: "update",
+			run: func(fsw *FilerStoreWrapper, ctx context.Context, entry *Entry) error {
+				return fsw.UpdateEntry(ctx, entry)
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		for _, op := range operations {
+			t.Run(tt.name+"/"+op.name, func(t *testing.T) {
+				store := newStubFilerStore()
+				wrapper := NewFilerStoreWrapper(store)
+				entry := &Entry{
+					FullPath: util.FullPath("/buckets/test/object"),
+					Attr: Attr{
+						Mode: tt.mode,
+						Mime: "application/octet-stream",
+					},
+				}
+
+				err := op.run(wrapper, context.Background(), entry)
+				require.NoError(t, err)
+
+				storedEntry, findErr := store.FindEntry(context.Background(), entry.FullPath)
+				require.NoError(t, findErr)
+				assert.Equal(t, tt.wantMime, storedEntry.Mime)
+			})
+		}
+	}
+}