Add option to preserve node marks when cloning a node

include/yaml-cpp/node/node.h

@@ -139,7 +139,7 @@ class YAML_CPP_API Node {
 
 YAML_CPP_API bool operator==(const Node& lhs, const Node& rhs);
 
-YAML_CPP_API Node Clone(const Node& node);
+YAML_CPP_API Node Clone(const Node& node, bool preserveMarks = false);
 
 template <typename T>
 struct convert;

src/node.cpp

@@ -3,10 +3,10 @@
 #include "nodeevents.h"
 
 namespace YAML {
-Node Clone(const Node& node) {
+Node Clone(const Node& node, bool preserveMarks) {
   NodeEvents events(node);
   NodeBuilder builder;
-  events.Emit(builder);
+  events.Emit(builder, preserveMarks);
   return builder.Root();
 }
 }  // namespace YAML

src/nodeevents.cpp

@@ -42,17 +42,17 @@ void NodeEvents::Setup(const detail::node& node) {
   }
 }
 
-void NodeEvents::Emit(EventHandler& handler) {
+void NodeEvents::Emit(EventHandler& handler, bool preserveMarks) {
   AliasManager am;
 
   handler.OnDocumentStart(Mark());
   if (m_root)
-    Emit(*m_root, handler, am);
+    Emit(*m_root, handler, am, preserveMarks);
   handler.OnDocumentEnd();
 }
 
 void NodeEvents::Emit(const detail::node& node, EventHandler& handler,
-                      AliasManager& am) const {
+                      AliasManager& am, bool preserveMarks) const {
   anchor_t anchor = NullAnchor;
   if (IsAliased(node)) {
     anchor = am.LookupAnchor(node);
@@ -65,26 +65,30 @@ void NodeEvents::Emit(const detail::node& node, EventHandler& handler,
     anchor = am.LookupAnchor(node);
   }
 
+  auto getMark = [preserveMarks, &node]() {
+    return preserveMarks ? node.mark() : Mark();
+  };
+
   switch (node.type()) {
     case NodeType::Undefined:
       break;
     case NodeType::Null:
-      handler.OnNull(Mark(), anchor);
+      handler.OnNull(getMark(), anchor);
       break;
     case NodeType::Scalar:
-      handler.OnScalar(Mark(), node.tag(), anchor, node.scalar());
+      handler.OnScalar(getMark(), node.tag(), anchor, node.scalar());
       break;
     case NodeType::Sequence:
-      handler.OnSequenceStart(Mark(), node.tag(), anchor, node.style());
+      handler.OnSequenceStart(getMark(), node.tag(), anchor, node.style());
       for (auto element : node)
-        Emit(*element, handler, am);
+        Emit(*element, handler, am, preserveMarks);
       handler.OnSequenceEnd();
       break;
     case NodeType::Map:
-      handler.OnMapStart(Mark(), node.tag(), anchor, node.style());
+      handler.OnMapStart(getMark(), node.tag(), anchor, node.style());
       for (auto element : node) {
-        Emit(*element.first, handler, am);
-        Emit(*element.second, handler, am);
+        Emit(*element.first, handler, am, preserveMarks);
+        Emit(*element.second, handler, am, preserveMarks);
       }
       handler.OnMapEnd();
       break;

src/nodeevents.h

@@ -31,7 +31,7 @@ class NodeEvents {
   NodeEvents& operator=(const NodeEvents&) = delete;
   NodeEvents& operator=(NodeEvents&&) = delete;
 
-  void Emit(EventHandler& handler);
+  void Emit(EventHandler& handler, bool preserveMarks = false);
 
  private:
   class AliasManager {
@@ -53,7 +53,7 @@ class NodeEvents {
 
   void Setup(const detail::node& node);
   void Emit(const detail::node& node, EventHandler& handler,
-            AliasManager& am) const;
+            AliasManager& am, bool preserveMarks) const;
   bool IsAliased(const detail::node& node) const;
 
  private:

test/integration/clone_node_test.cpp

@@ -0,0 +1,92 @@
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include <yaml-cpp/yaml.h>
+
+struct ComparableMark {
+  int pos;
+  int line, column;
+
+  ComparableMark(int pos, int line, int column)
+      : pos(pos), line(line), column(column) {}
+};
+
+
+bool operator==(const YAML::Mark& a, const ComparableMark& b) {
+  return a.pos == b.pos && a.line == b.line && a.column == b.column;
+}
+
+template <typename Mark>
+void PrintMark(const Mark& mark, std::ostream* os) {
+  *os << mark.line << ':' << mark.column << " (pos " << mark.pos << ')';
+}
+
+void PrintTo(const ComparableMark& mark, std::ostream* os) {
+  PrintMark(mark, os);
+}
+
+namespace YAML {
+  void PrintTo(const Mark& mark, std::ostream* os) {
+    PrintMark(mark, os);
+  }
+}
+
+TEST(CloneNodeTest, PreserveMark) {
+  std::string yaml_str = R"(
+scalar: value
+sequence: [1, 2, 3]
+"null": null
+[1, 2, 3]: value  # check non-scalar keys
+)";
+
+  auto checkMarks = [](const YAML::Node& root_node) {
+    EXPECT_EQ(root_node.Mark(), ComparableMark(1, 1, 0));
+
+    const YAML::Node& scalar = root_node["scalar"];
+    EXPECT_EQ(scalar.Mark(), ComparableMark(9, 1, 8));
+
+    const YAML::Node& sequence = root_node["sequence"];
+    EXPECT_EQ(sequence.Mark(), ComparableMark(25, 2, 10));
+    EXPECT_EQ(sequence[0].Mark(), ComparableMark(26, 2, 11));
+    EXPECT_EQ(sequence[1].Mark(), ComparableMark(29, 2, 14));
+    EXPECT_EQ(sequence[2].Mark(), ComparableMark(32, 2, 17));
+
+    const YAML::Node& null = root_node["null"];
+    EXPECT_EQ(null.Mark(), ComparableMark(43, 3, 8));
+
+    YAML::Node sequence_key;
+    std::vector<YAML::Mark> key_marks;
+    for (auto it = root_node.begin(); it != root_node.end(); ++it) {
+      // Not assuming any key order
+      key_marks.emplace_back(it->first.Mark());
+      if (it->first.IsSequence()) {
+        sequence_key.reset(it->first);
+      }
+    }
+
+    EXPECT_THAT(
+      key_marks,
+      testing::UnorderedElementsAre(
+        ComparableMark(1, 1, 0),
+        ComparableMark(15, 2, 0),
+        ComparableMark(35, 3, 0),
+        ComparableMark(48, 4, 0)
+      )
+    );
+
+    ASSERT_TRUE(sequence_key);
+    EXPECT_EQ(sequence_key[0].Mark(), ComparableMark(49, 4, 1));
+    EXPECT_EQ(sequence_key[1].Mark(), ComparableMark(52, 4, 4));
+    EXPECT_EQ(sequence_key[2].Mark(), ComparableMark(55, 4, 7));
+  };
+
+  YAML::Node root_node = YAML::Load(yaml_str);
+  {
+    SCOPED_TRACE("original node");
+    checkMarks(root_node);
+  }
+  YAML::Node cloned_node = YAML::Clone(root_node, true);
+  {
+    SCOPED_TRACE("cloned node");
+    checkMarks(cloned_node);
+  }
+}