1 files changed, 65 insertions, 0 deletions
diff --git a/hugofs/dirsmerger.go b/hugofs/dirsmerger.go
new file mode 100644
index 000000000..392353e27
--- /dev/null
+++ b/hugofs/dirsmerger.go
@@ -0,0 +1,65 @@
+// Copyright 2024 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package hugofs
+
+import (
+	"io/fs"
+
+	"github.com/bep/overlayfs"
+)
+
+// LanguageDirsMerger implements the overlayfs.DirsMerger func, which is used
+// to merge two directories.
+var LanguageDirsMerger overlayfs.DirsMerger = func(lofi, bofi []fs.DirEntry) []fs.DirEntry {
+	for _, fi1 := range bofi {
+		fim1 := fi1.(FileMetaInfo)
+		var found bool
+		for _, fi2 := range lofi {
+			fim2 := fi2.(FileMetaInfo)
+			if fi1.Name() == fi2.Name() && fim1.Meta().Lang == fim2.Meta().Lang {
+				found = true
+				break
+			}
+		}
+		if !found {
+			lofi = append(lofi, fi1)
+		}
+	}
+
+	return lofi
+}
+
+// AppendDirsMerger merges two directories keeping all regular files
+// with the first slice as the base.
+// Duplicate directories in the secnond slice will be ignored.
+// This strategy is used for the i18n and data fs where we need all entries.
+var AppendDirsMerger overlayfs.DirsMerger = func(lofi, bofi []fs.DirEntry) []fs.DirEntry {
+	for _, fi1 := range bofi {
+		var found bool
+		// Remove duplicate directories.
+		if fi1.IsDir() {
+			for _, fi2 := range lofi {
+				if fi2.IsDir() && fi2.Name() == fi1.Name() {
+					found = true
+					break
+				}
+			}
+		}
+		if !found {
+			lofi = append(lofi, fi1)
+		}
+	}
+
+	return lofi
+}