Add Nullable reference type annotations

src/SharpYaml/Emitter.cs

@@ -90,9 +90,9 @@ public class Emitter : IEmitter
 
         private class MutableStringLookAheadBuffer : ILookAheadBuffer
         {
-            private string value;
+            private string? value;
 
-            public string Value
+            public string? Value
             {
                 get { return value; }
                 set
@@ -135,16 +135,16 @@ public void Cache(int length) { }
 
         private struct AnchorData
         {
-            public string anchor;
+            public string? anchor;
             public bool isAlias;
         }
 
         private AnchorData anchorData;
 
         private struct TagData
         {
-            public string handle;
-            public string suffix;
+            public string? handle;
+            public string? suffix;
         }
 
         private TagData tagData;
@@ -313,7 +313,7 @@ private bool NeedMoreEvents()
             return true;
         }
 
-        private void AnalyzeAnchor(string anchor, bool isAlias)
+        private void AnalyzeAnchor(string? anchor, bool isAlias)
         {
             anchorData.anchor = anchor;
             anchorData.isAlias = isAlias;
@@ -1680,7 +1680,7 @@ private void EmitFlowMappingKey(ParsingEvent evt, bool isFirst)
 
         private const int MaxAliasLength = 128;
 
-        private static int SafeStringLength(string value)
+        private static int SafeStringLength(string? value)
         {
             return value != null ? value.Length : 0;
         }
@@ -1851,7 +1851,7 @@ private void WriteBlockScalarHints(string value)
 
             isOpenEnded = false;
 
-            string chomp_hint = null;
+            string? chomp_hint = null;
             if (value.Length == 0 || !analyzer.IsBreak(value.Length - 1))
             {
                 chomp_hint = "-";

src/SharpYaml/EventReader.cs

@@ -128,13 +128,13 @@ public bool Accept<T>() where T : Event
         /// </summary>
         /// <typeparam name="T">Type of the <see cref="Event"/>.</typeparam>
         /// <returns>Returns the current event if it is of type T; otherwise returns null.</returns>
-        public T Allow<T>() where T : Event
+        public T? Allow<T>() where T : Event
         {
             if (!Accept<T>())
             {
                 return null;
             }
-            var yamlEvent = (T)Parser.Current;
+            var yamlEvent = (T?)Parser.Current;
             MoveNext();
             return yamlEvent;
         }
@@ -144,13 +144,13 @@ public T Allow<T>() where T : Event
         /// </summary>
         /// <typeparam name="T">Type of the <see cref="Event"/>.</typeparam>
         /// <returns>Returns the current event if it is of type T; otherwise returns null.</returns>
-        public T Peek<T>() where T : Event
+        public T? Peek<T>() where T : Event
         {
             if (!Accept<T>())
             {
                 return null;
             }
-            var yamlEvent = (T)Parser.Current;
+            var yamlEvent = (T?)Parser.Current;
             return yamlEvent;
         }
 

src/SharpYaml/Events/DocumentStart.cs

@@ -70,13 +70,13 @@ public sealed class DocumentStart : ParsingEvent
         /// Gets the tags.
         /// </summary>
         /// <value>The tags.</value>
-        public TagDirectiveCollection Tags { get; }
+        public TagDirectiveCollection? Tags { get; }
 
         /// <summary>
         /// Gets the version.
         /// </summary>
         /// <value>The version.</value>
-        public VersionDirective Version { get; }
+        public VersionDirective? Version { get; }
 
         /// <summary>
         /// Gets a value indicating whether this instance is implicit.
@@ -94,7 +94,7 @@ public sealed class DocumentStart : ParsingEvent
         /// <param name="isImplicit">Indicates whether the event is implicit.</param>
         /// <param name="start">The start position of the event.</param>
         /// <param name="end">The end position of the event.</param>
-        public DocumentStart(VersionDirective version, TagDirectiveCollection tags, bool isImplicit, Mark start, Mark end)
+        public DocumentStart(VersionDirective? version, TagDirectiveCollection? tags, bool isImplicit, Mark start, Mark end)
             : base(start, end)
         {
             this.Version = version;
@@ -108,7 +108,7 @@ public DocumentStart(VersionDirective version, TagDirectiveCollection tags, bool
         /// <param name="version">The version.</param>
         /// <param name="tags">The tags.</param>
         /// <param name="isImplicit">Indicates whether the event is implicit.</param>
-        public DocumentStart(VersionDirective version, TagDirectiveCollection tags, bool isImplicit)
+        public DocumentStart(VersionDirective? version, TagDirectiveCollection? tags, bool isImplicit)
             : this(version, tags, isImplicit, Mark.Empty, Mark.Empty)
         {
         }

src/SharpYaml/Events/MappingStart.cs

@@ -93,7 +93,7 @@ public sealed class MappingStart : NodeEvent
         /// <param name="style">The style of the mapping.</param>
         /// <param name="start">The start position of the event.</param>
         /// <param name="end">The end position of the event.</param>
-        public MappingStart(string anchor, string tag, bool isImplicit, YamlStyle style, Mark start, Mark end)
+        public MappingStart(string? anchor, string? tag, bool isImplicit, YamlStyle style, Mark start, Mark end)
             : base(anchor, tag, start, end)
         {
             this.IsImplicit = isImplicit;
@@ -107,7 +107,7 @@ public MappingStart(string anchor, string tag, bool isImplicit, YamlStyle style,
         /// <param name="tag">The tag.</param>
         /// <param name="isImplicit">Indicates whether the event is implicit.</param>
         /// <param name="style">The style of the mapping.</param>
-        public MappingStart(string anchor, string tag, bool isImplicit, YamlStyle style)
+        public MappingStart(string? anchor, string? tag, bool isImplicit, YamlStyle style)
             : this(anchor, tag, isImplicit, style, Mark.Empty, Mark.Empty)
         {
         }

src/SharpYaml/Events/NodeEvent.cs

@@ -59,13 +59,13 @@ public abstract class NodeEvent : ParsingEvent
         /// Gets the anchor.
         /// </summary>
         /// <value></value>
-        public string Anchor { get; }
+        public string? Anchor { get; }
 
         /// <summary>
         /// Gets the tag.
         /// </summary>
         /// <value></value>
-        public string Tag { get; }
+        public string? Tag { get; }
 
         /// <summary>
         /// Gets a value indicating whether this instance is canonical.
@@ -80,7 +80,7 @@ public abstract class NodeEvent : ParsingEvent
         /// <param name="tag">The tag.</param>
         /// <param name="start">The start position of the event.</param>
         /// <param name="end">The end position of the event.</param>
-        protected NodeEvent(string anchor, string tag, Mark start, Mark end)
+        protected NodeEvent(string? anchor, string? tag, Mark start, Mark end)
             : base(start, end)
         {
             if (anchor != null)
@@ -108,7 +108,7 @@ protected NodeEvent(string anchor, string tag, Mark start, Mark end)
         /// <summary>
         /// Initializes a new instance of the <see cref="NodeEvent"/> class.
         /// </summary>
-        protected NodeEvent(string anchor, string tag)
+        protected NodeEvent(string? anchor, string? tag)
             : this(anchor, tag, Mark.Empty, Mark.Empty)
         {
         }

src/SharpYaml/Events/Scalar.cs

@@ -105,7 +105,7 @@ public sealed class Scalar : NodeEvent
         /// <param name="isQuotedImplicit">.</param>
         /// <param name="start">The start position of the event.</param>
         /// <param name="end">The end position of the event.</param>
-        public Scalar(string anchor, string tag, string value, ScalarStyle style, bool isPlainImplicit, bool isQuotedImplicit, Mark start, Mark end)
+        public Scalar(string? anchor, string? tag, string value, ScalarStyle style, bool isPlainImplicit, bool isQuotedImplicit, Mark start, Mark end)
             : base(anchor, tag, start, end)
         {
             this.Value = value;
@@ -123,7 +123,7 @@ public Scalar(string anchor, string tag, string value, ScalarStyle style, bool i
         /// <param name="style">The style.</param>
         /// <param name="isPlainImplicit">.</param>
         /// <param name="isQuotedImplicit">.</param>
-        public Scalar(string anchor, string tag, string value, ScalarStyle style, bool isPlainImplicit, bool isQuotedImplicit)
+        public Scalar(string? anchor, string? tag, string value, ScalarStyle style, bool isPlainImplicit, bool isQuotedImplicit)
             : this(anchor, tag, value, style, isPlainImplicit, isQuotedImplicit, Mark.Empty, Mark.Empty)
         {
         }
@@ -152,7 +152,7 @@ public Scalar(string value, ScalarStyle style)
         /// </summary>
         /// <param name="tag">The tag.</param>
         /// <param name="value">The value.</param>
-        public Scalar(string tag, string value)
+        public Scalar(string? tag, string value)
             : this(null, tag, value, ScalarStyle.Any, true, true, Mark.Empty, Mark.Empty)
         {
         }

src/SharpYaml/Events/SequenceStart.cs

@@ -101,7 +101,7 @@ public SequenceStart() : base(null, null)
         /// <param name="style">The style.</param>
         /// <param name="start">The start position of the event.</param>
         /// <param name="end">The end position of the event.</param>
-        public SequenceStart(string anchor, string tag, bool isImplicit, YamlStyle style, Mark start, Mark end)
+        public SequenceStart(string? anchor, string? tag, bool isImplicit, YamlStyle style, Mark start, Mark end)
             : base(anchor, tag, start, end)
         {
             this.IsImplicit = isImplicit;
@@ -111,7 +111,7 @@ public SequenceStart(string anchor, string tag, bool isImplicit, YamlStyle style
         /// <summary>
         /// Initializes a new instance of the <see cref="SequenceStart"/> class.
         /// </summary>
-        public SequenceStart(string anchor, string tag, bool isImplicit, YamlStyle style)
+        public SequenceStart(string? anchor, string? tag, bool isImplicit, YamlStyle style)
             : this(anchor, tag, isImplicit, style, Mark.Empty, Mark.Empty)
         {
         }

src/SharpYaml/IParser.cs

@@ -55,7 +55,7 @@ public interface IParser
         /// <summary>
         /// Gets the current event.
         /// </summary>
-        ParsingEvent Current { get; }
+        ParsingEvent? Current { get; }
 
         /// <summary>
         /// Moves to the next event.

src/SharpYaml/Model/PathTrie.cs

@@ -58,7 +58,7 @@ public bool IsEmpty
                 get { return !Self && subPaths.Count == 0; }
             }
 
-            public PathTrieNode Find(IList<ChildIndex> indices, int start)
+            public PathTrieNode? Find(IList<ChildIndex> indices, int start)
             {
                 if (start == indices.Count)
                     return this;

src/SharpYaml/Model/YamlDocument.cs

@@ -29,15 +29,15 @@ public class YamlDocument : YamlNode
     {
         private DocumentStart _documentStart;
         private DocumentEnd _documentEnd;
-        private YamlElement _contents;
+        private YamlElement? _contents;
 
         public YamlDocument()
         {
             _documentStart = new DocumentStart(null, new TagDirectiveCollection(), true);
             _documentEnd = new DocumentEnd(true);
         }
 
-        YamlDocument(DocumentStart documentStart, DocumentEnd documentEnd, YamlElement contents, YamlNodeTracker tracker)
+        YamlDocument(DocumentStart documentStart, DocumentEnd documentEnd, YamlElement? contents, YamlNodeTracker? tracker)
         {
             Tracker = tracker;
 
@@ -46,7 +46,7 @@ public YamlDocument()
             Contents = contents;
         }
 
-        public static YamlDocument Load(EventReader eventReader, YamlNodeTracker tracker = null)
+        public static YamlDocument Load(EventReader eventReader, YamlNodeTracker? tracker = null)
         {
             var documentStart = eventReader.Allow<DocumentStart>();
 
@@ -85,7 +85,7 @@ public DocumentEnd DocumentEnd
             }
         }
 
-        public YamlElement Contents
+        public YamlElement? Contents
         {
             get { return _contents; }
             set
@@ -102,7 +102,7 @@ public YamlElement Contents
             }
         }
 
-        public override YamlNodeTracker Tracker
+        public override YamlNodeTracker? Tracker
         {
             get { return base.Tracker; }
             internal set
@@ -120,9 +120,9 @@ internal set
             }
         }
 
-        public override YamlNode DeepClone(YamlNodeTracker tracker = null)
+        public override YamlNode DeepClone(YamlNodeTracker? tracker = null)
         {
-            return new YamlDocument(_documentStart, _documentEnd, (YamlElement)Contents?.DeepClone(), tracker);
+            return new YamlDocument(_documentStart, _documentEnd, (YamlElement?)Contents?.DeepClone(), tracker);
         }
     }
 }

src/SharpYaml/Model/YamlElement.cs

@@ -21,8 +21,8 @@ namespace SharpYaml.Model
 {
     public abstract class YamlElement : YamlNode
     {
-        public abstract string Anchor { get; set; }
-        public abstract string Tag { get; set; }
+        public abstract string? Anchor { get; set; }
+        public abstract string? Tag { get; set; }
         public abstract bool IsCanonical { get; }
     }
 }