fix(s3api): ListObjects with trailing-slash prefix matches sibling directories (#8599)

fix(s3api): ListObjects with trailing-slash prefix returns wrong results

When ListObjectsV2 is called with a prefix ending in "/" (e.g., "foo/"),
normalizePrefixMarker strips the trailing slash and splits into
dir="parent" and prefix="foo". The filer then lists entries matching
prefix "foo", which returns both directory "foo" and "foo1000".

The prefixEndsOnDelimiter guard correctly identifies directory "foo" as
the target and recurses into it, but then resets the guard to false.
The loop continues and incorrectly recurses into "foo1000" as well,
causing the listing to return objects from unrelated directories.

Fix: after recursing into the exact directory targeted by the
trailing-slash prefix, return immediately from the listing loop.
There is no reason to process sibling entries since the original
prefix specifically targeted one directory.

weed/s3api/s3api_object_handlers_list.go

@@ -632,6 +632,10 @@ func (s3a *S3ApiServer) doListFilerEntries(client filer_pb.SeaweedFilerClient, d
 
 		// Set nextMarker only when we have quota to process this entry
 		nextMarker = entry.Name
+		// Track whether this entry is the exact directory targeted by a trailing-slash prefix
+		// (e.g., prefix "foo" from original prefix "foo/"). After recursing into this directory,
+		// we must stop processing siblings to avoid matching unrelated entries like "foo1000".
+		matchedPrefixDir := cursor.prefixEndsOnDelimiter && entry.Name == prefix && entry.IsDirectory
 		if cursor.prefixEndsOnDelimiter {
 			if entry.Name == prefix && entry.IsDirectory {
 				if delimiter != "/" {
@@ -692,6 +696,9 @@ func (s3a *S3ApiServer) doListFilerEntries(client filer_pb.SeaweedFilerClient, d
 				if cursor.isTruncated {
 					return
 				}
+				if matchedPrefixDir {
+					return
+				}
 				// println("doListFilerEntries2 nextMarker", nextMarker)
 			} else {
 				eachEntryFn(dir, entry)

weed/s3api/s3api_object_handlers_list_test.go

@@ -814,3 +814,74 @@ func TestListObjectsV2_Regression_Sorting(t *testing.T) {
 	// With fix, it sees both and processes "reports"
 	assert.Contains(t, results, "file1", "Should return the nested file even if 'reports' directory is not the first match")
 }
+
+func TestListObjectsV2_PrefixEndingWithSlash_DoesNotMatchSiblings(t *testing.T) {
+	// Regression test: listing with prefix "1/" should only return objects under
+	// directory "1", not objects under "1000" or any other sibling whose name
+	// shares the same prefix string.
+
+	s3a := &S3ApiServer{}
+	client := &testFilerClient{
+		entriesByDir: map[string][]*filer_pb.Entry{
+			"/buckets/bucket/path/to/list": {
+				{Name: "1", IsDirectory: true, Attributes: &filer_pb.FuseAttributes{}},
+				{Name: "1000", IsDirectory: true, Attributes: &filer_pb.FuseAttributes{}},
+				{Name: "2500", IsDirectory: true, Attributes: &filer_pb.FuseAttributes{}},
+			},
+			"/buckets/bucket/path/to/list/1": {
+				{Name: "fileA", IsDirectory: false, Attributes: &filer_pb.FuseAttributes{}},
+			},
+			"/buckets/bucket/path/to/list/1000": {
+				{Name: "fileB", IsDirectory: false, Attributes: &filer_pb.FuseAttributes{}},
+				{Name: "fileC", IsDirectory: false, Attributes: &filer_pb.FuseAttributes{}},
+			},
+			"/buckets/bucket/path/to/list/2500": {
+				{Name: "fileD", IsDirectory: false, Attributes: &filer_pb.FuseAttributes{}},
+			},
+		},
+	}
+
+	// Simulate listing with prefix "path/to/list/1/" (no delimiter).
+	// normalizePrefixMarker("path/to/list/1/", "") returns dir="path/to/list", prefix="1"
+	cursor := &ListingCursor{maxKeys: 1000, prefixEndsOnDelimiter: true}
+	var results []string
+
+	_, err := s3a.doListFilerEntries(client, "/buckets/bucket/path/to/list", "1", cursor, "", "", false, "bucket", func(dir string, entry *filer_pb.Entry) {
+		if !entry.IsDirectory {
+			results = append(results, entry.Name)
+		}
+	})
+
+	assert.NoError(t, err)
+	assert.Equal(t, []string{"fileA"}, results, "Should only return files under directory '1', not '1000' or '2500'")
+}
+
+func TestListObjectsV2_PrefixEndingWithSlash_WithDelimiter(t *testing.T) {
+	// Same scenario but with delimiter="/", verifying the fix works for both cases.
+
+	s3a := &S3ApiServer{}
+	client := &testFilerClient{
+		entriesByDir: map[string][]*filer_pb.Entry{
+			"/buckets/bucket/path/to/list": {
+				{Name: "1", IsDirectory: true, Attributes: &filer_pb.FuseAttributes{}},
+				{Name: "1000", IsDirectory: true, Attributes: &filer_pb.FuseAttributes{}},
+			},
+			"/buckets/bucket/path/to/list/1": {
+				{Name: "fileA", IsDirectory: false, Attributes: &filer_pb.FuseAttributes{}},
+			},
+			"/buckets/bucket/path/to/list/1000": {
+				{Name: "fileB", IsDirectory: false, Attributes: &filer_pb.FuseAttributes{}},
+			},
+		},
+	}
+
+	cursor := &ListingCursor{maxKeys: 1000, prefixEndsOnDelimiter: true}
+	var results []string
+
+	_, err := s3a.doListFilerEntries(client, "/buckets/bucket/path/to/list", "1", cursor, "", "/", false, "bucket", func(dir string, entry *filer_pb.Entry) {
+		results = append(results, entry.Name)
+	})
+
+	assert.NoError(t, err)
+	assert.Equal(t, []string{"fileA"}, results, "Should only return files under directory '1', not '1000'")
+}