Merge pull request #222 from mlaily/allow-anchor-overwriting

Allow anchors redefinition/overwriting

Author: aaubry

YamlDotNet.Test/RepresentationModel/YamlStreamTests.cs

@@ -204,6 +204,12 @@ public void Roundtrip32BitsUnicodeEscape()
         {
             RoundtripTest("unicode-32bits-escape.yaml");
         }
+        
+        [Fact]
+        public void AnchorsOverwriting()
+        {
+            RoundtripTest("anchors-overwriting.yaml");
+        }
 
         [Fact]
         public void AllAliasesMustBeResolved()

YamlDotNet.Test/Serialization/SerializationTests.cs

@@ -1371,6 +1371,24 @@ public void DeserializationOfInt64Succeeds(long value)
             Assert.Equal(value, parsed);
         }
 
+        public class AnchorsOverwritingTestCase
+        {
+            public List<string> a { get; set; }
+            public List<string> b { get; set; }
+            public List<string> c { get; set; }
+            public List<string> d { get; set; }
+        }
+
+        [Fact]
+        public void DeserializationOfStreamWithDuplicateAnchorsSucceeds()
+        {
+            var yaml = Yaml.ParserForResource("anchors-overwriting.yaml");
+            var serializer = new DeserializerBuilder()
+                .IgnoreUnmatchedProperties()
+                .Build();
+            var deserialized = serializer.Deserialize<AnchorsOverwritingTestCase>(yaml);
+        }
+
         [Fact]
         public void SerializeExceptionWithStackTrace()
         {

YamlDotNet.Test/YamlDotNet.Test.csproj

@@ -141,6 +141,7 @@
     <EmbeddedResource Include="files\ordered-properties.yaml" />
     <EmbeddedResource Include="files\multi-doc-tag.yaml" />
     <EmbeddedResource Include="files\unicode-32bits-escape.yaml" />
+    <EmbeddedResource Include="files\anchors-overwriting.yaml" />
     <None Include="packages.config" />
   </ItemGroup>
   <ItemGroup>

YamlDotNet.Test/files/anchors-overwriting.yaml

@@ -0,0 +1,9 @@
+a : &anchor [foo]
+c : *anchor
+b : &anchor [bar]
+d : *anchor
+
+e : &anchor2 baz
+g : *anchor2
+f : &anchor2 foobar
+h : *anchor2

YamlDotNet/Core/DuplicateAnchorException.cs

@@ -47,10 +47,12 @@ public void AddAnchor(YamlNode node)
 
             if (anchors.ContainsKey(node.Anchor))
             {
-                throw new DuplicateAnchorException(node.Start, node.End, string.Format(CultureInfo.InvariantCulture, "The anchor '{0}' already exists", node.Anchor));
+                anchors[node.Anchor] = node;
+            }
+            else
+            {
+                anchors.Add(node.Anchor, node);
             }
-
-            anchors.Add(node.Anchor, node);
         }
 
         /// <summary>

YamlDotNet/RepresentationModel/DocumentLoadingState.cs

@@ -82,11 +82,15 @@ internal YamlDocument(IParser parser)
         }
 
         /// <summary>
-        /// Visitor that assigns anchors to nodes that are referenced more than once but have no anchor.
+        /// Visitor that assigns anchors to nodes that are referenced more than once.
+        /// Existing anchors are preserved as much as possible.
         /// </summary>
         private class AnchorAssigningVisitor : YamlVisitorBase
         {
             private readonly HashSet<string> existingAnchors = new HashSet<string>();
+            /// <summary>
+            /// Key: Node, Value: IsDuplicate
+            /// </summary>
             private readonly Dictionary<YamlNode, bool> visitedNodes = new Dictionary<YamlNode, bool>();
 
             public void AssignAnchors(YamlDocument document)
@@ -102,55 +106,61 @@ public void AssignAnchors(YamlDocument document)
                     if (visitedNode.Value)
                     {
                         string anchor;
-                        do
+                        // If the existing anchor is not already used, we can have it
+                        if (!string.IsNullOrEmpty(visitedNode.Key.Anchor) && !existingAnchors.Contains(visitedNode.Key.Anchor))
                         {
-                            anchor = random.Next().ToString(CultureInfo.InvariantCulture);
-                        } while (existingAnchors.Contains(anchor));
-                        existingAnchors.Add(anchor);
+                            anchor = visitedNode.Key.Anchor;
+                        }
+                        else
+                        {
+                            do
+                            {
+                                anchor = random.Next().ToString(CultureInfo.InvariantCulture);
+                            } while (existingAnchors.Contains(anchor));
+                        }
 
+                        existingAnchors.Add(anchor);
                         visitedNode.Key.Anchor = anchor;
                     }
                 }
             }
 
-            private void VisitNode(YamlNode node)
+            /// <summary>
+            /// Returns whether the visited node is a duplicate.
+            /// </summary>
+            private bool VisitNodeAndFindDuplicates(YamlNode node)
             {
-                if (string.IsNullOrEmpty(node.Anchor))
+                bool isDuplicate;
+                if (visitedNodes.TryGetValue(node, out isDuplicate))
                 {
-                    bool isDuplicate;
-                    if (visitedNodes.TryGetValue(node, out isDuplicate))
-                    {
-                        if (!isDuplicate)
-                        {
-                            visitedNodes[node] = true;
-                        }
-                    }
-                    else
+                    if (!isDuplicate)
                     {
-                        visitedNodes.Add(node, false);
+                        visitedNodes[node] = true;
                     }
+                    return !isDuplicate;
                 }
                 else
                 {
-                    existingAnchors.Add(node.Anchor);
+                    visitedNodes.Add(node, false);
+                    return false;
                 }
             }
 
             public override void Visit(YamlScalarNode scalar)
             {
-                // Do not assign anchors to scalars
+                VisitNodeAndFindDuplicates(scalar);
             }
 
             public override void Visit(YamlMappingNode mapping)
             {
-                VisitNode(mapping);
-                base.Visit(mapping);
+                if (!VisitNodeAndFindDuplicates(mapping))
+                    base.Visit(mapping);
             }
 
             public override void Visit(YamlSequenceNode sequence)
             {
-                VisitNode(sequence);
-                base.Visit(sequence);
+                if (!VisitNodeAndFindDuplicates(sequence))
+                    base.Visit(sequence);
             }
         }
 

YamlDotNet/RepresentationModel/YamlDocument.cs

@@ -106,7 +106,7 @@ public object Value
             }
         }
 
-        public object DeserializeValue (IParser parser, Type expectedType, SerializerState state, IValueDeserializer nestedObjectDeserializer)
+        public object DeserializeValue(IParser parser, Type expectedType, SerializerState state, IValueDeserializer nestedObjectDeserializer)
         {
             object value;
             var alias = parser.Allow<AnchorAlias>();
@@ -148,10 +148,7 @@ public object DeserializeValue (IParser parser, Type expectedType, SerializerSta
                 }
                 else
                 {
-                    throw new DuplicateAnchorException(nodeEvent.Start, nodeEvent.End, string.Format(
-                        "Anchor '{0}' already defined",
-                        anchor
-                    ));
+                    aliasState[anchor] = new ValuePromise(value);
                 }
             }
 

YamlDotNet/Serialization/ValueDeserializers/AliasValueDeserializer.cs

@@ -148,7 +148,6 @@
     <Compile Include="Core\CharacterAnalyzer.cs" />
     <Compile Include="Core\Constants.cs" />
     <Compile Include="Core\Cursor.cs" />
-    <Compile Include="Core\DuplicateAnchorException.cs" />
     <Compile Include="Core\Emitter.cs" />
     <Compile Include="Core\EmitterState.cs" />
     <Compile Include="Core\ParserExtensions.cs" />