Enable serialization of `TagHelperDescriptor`s.

- Added ability for TagHelpers to write their own json output.

src/Microsoft.VisualStudio.LanguageServices.Razor/Serialization/TagHelperDescriptorJsonConverter.cs

@@ -13,8 +13,6 @@ namespace Microsoft.VisualStudio.LanguageServices.Razor.Serialization
     {
         public static readonly TagHelperDescriptorJsonConverter Instance = new TagHelperDescriptorJsonConverter();
 
-        public override bool CanWrite => false;
-
         public override bool CanConvert(Type objectType)
         {
             return typeof(TagHelperDescriptor).IsAssignableFrom(objectType);
@@ -81,9 +79,166 @@ namespace Microsoft.VisualStudio.LanguageServices.Razor.Serialization
 
         public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
         {
-            // We should never get here because CanWrite returns false.
+            var tagHelper = (TagHelperDescriptor)value;
-            // We want the default serializer to handle TagHelperDescriptor serialization.
+
-            throw new NotImplementedException();
+            writer.WriteStartObject();
+
+            writer.WritePropertyName(nameof(TagHelperDescriptor.Kind));
+            writer.WriteValue(tagHelper.Kind);
+
+            writer.WritePropertyName(nameof(TagHelperDescriptor.Name));
+            writer.WriteValue(tagHelper.Name);
+
+            writer.WritePropertyName(nameof(TagHelperDescriptor.AssemblyName));
+            writer.WriteValue(tagHelper.AssemblyName);
+
+            writer.WritePropertyName(nameof(TagHelperDescriptor.Documentation));
+            writer.WriteValue(tagHelper.Documentation);
+
+            writer.WritePropertyName(nameof(TagHelperDescriptor.TagOutputHint));
+            writer.WriteValue(tagHelper.TagOutputHint);
+
+            writer.WritePropertyName(nameof(TagHelperDescriptor.TagMatchingRules));
+            writer.WriteStartArray();
+            foreach (var ruleDescriptor in tagHelper.TagMatchingRules)
+            {
+                WriteTagMatchingRule(writer, ruleDescriptor, serializer);
+            }
+            writer.WriteEndArray();
+
+            writer.WritePropertyName(nameof(TagHelperDescriptor.BoundAttributes));
+            writer.WriteStartArray();
+            foreach (var boundAttribute in tagHelper.BoundAttributes)
+            {
+                WriteBoundAttribute(writer, boundAttribute, serializer);
+            }
+            writer.WriteEndArray();
+
+            writer.WritePropertyName(nameof(TagHelperDescriptor.AllowedChildTags));
+            writer.WriteStartArray();
+            foreach (var allowedChildTag in tagHelper.AllowedChildTags)
+            {
+                WriteAllowedChildTags(writer, allowedChildTag, serializer);
+            }
+            writer.WriteEndArray();
+
+            writer.WritePropertyName(nameof(TagHelperDescriptor.Diagnostics));
+            serializer.Serialize(writer, tagHelper.Diagnostics);
+
+            writer.WritePropertyName(nameof(TagHelperDescriptor.Metadata));
+            WriteMetadata(writer, tagHelper.Metadata);
+
+            writer.WriteEndObject();
+        }
+
+        private void WriteAllowedChildTags(JsonWriter writer, AllowedChildTagDescriptor allowedChildTag, JsonSerializer serializer)
+        {
+            writer.WriteStartObject();
+
+            writer.WritePropertyName(nameof(AllowedChildTagDescriptor.Name));
+            writer.WriteValue(allowedChildTag.Name);
+
+            writer.WritePropertyName(nameof(AllowedChildTagDescriptor.DisplayName));
+            writer.WriteValue(allowedChildTag.DisplayName);
+
+            writer.WritePropertyName(nameof(AllowedChildTagDescriptor.Diagnostics));
+            serializer.Serialize(writer, allowedChildTag.Diagnostics);
+
+            writer.WriteEndObject();
+        }
+
+        private void WriteBoundAttribute(JsonWriter writer, BoundAttributeDescriptor boundAttribute, JsonSerializer serializer)
+        {
+            writer.WriteStartObject();
+
+            writer.WritePropertyName(nameof(BoundAttributeDescriptor.Kind));
+            writer.WriteValue(boundAttribute.Kind);
+
+            writer.WritePropertyName(nameof(BoundAttributeDescriptor.Name));
+            writer.WriteValue(boundAttribute.Name);
+
+            writer.WritePropertyName(nameof(BoundAttributeDescriptor.TypeName));
+            writer.WriteValue(boundAttribute.TypeName);
+
+            writer.WritePropertyName(nameof(BoundAttributeDescriptor.IsEnum));
+            writer.WriteValue(boundAttribute.IsEnum);
+
+            writer.WritePropertyName(nameof(BoundAttributeDescriptor.IndexerNamePrefix));
+            writer.WriteValue(boundAttribute.IndexerNamePrefix);
+
+            writer.WritePropertyName(nameof(BoundAttributeDescriptor.IndexerTypeName));
+            writer.WriteValue(boundAttribute.IndexerTypeName);
+
+            writer.WritePropertyName(nameof(BoundAttributeDescriptor.Documentation));
+            writer.WriteValue(boundAttribute.Documentation);
+
+            writer.WritePropertyName(nameof(BoundAttributeDescriptor.Diagnostics));
+            serializer.Serialize(writer, boundAttribute.Diagnostics);
+
+            writer.WritePropertyName(nameof(BoundAttributeDescriptor.Metadata));
+            WriteMetadata(writer, boundAttribute.Metadata);
+
+            writer.WriteEndObject();
+        }
+
+        private static void WriteMetadata(JsonWriter writer, IReadOnlyDictionary<string, string> metadata)
+        {
+            writer.WriteStartObject();
+            foreach (var kvp in metadata)
+            {
+                writer.WritePropertyName(kvp.Key);
+                writer.WriteValue(kvp.Value);
+            }
+            writer.WriteEndObject();
+        }
+
+        private void WriteTagMatchingRule(JsonWriter writer, TagMatchingRuleDescriptor ruleDescriptor, JsonSerializer serializer)
+        {
+            writer.WriteStartObject();
+
+            writer.WritePropertyName(nameof(TagMatchingRuleDescriptor.TagName));
+            writer.WriteValue(ruleDescriptor.TagName);
+
+            writer.WritePropertyName(nameof(TagMatchingRuleDescriptor.ParentTag));
+            writer.WriteValue(ruleDescriptor.ParentTag);
+
+            writer.WritePropertyName(nameof(TagMatchingRuleDescriptor.TagStructure));
+            writer.WriteValue(ruleDescriptor.TagStructure);
+
+            writer.WritePropertyName(nameof(TagMatchingRuleDescriptor.Attributes));
+            writer.WriteStartArray();
+            foreach (var requiredAttribute in ruleDescriptor.Attributes)
+            {
+                WriteRequiredAttribute(writer, requiredAttribute, serializer);
+            }
+            writer.WriteEndArray();
+
+            writer.WritePropertyName(nameof(TagMatchingRuleDescriptor.Diagnostics));
+            serializer.Serialize(writer, ruleDescriptor.Diagnostics);
+
+            writer.WriteEndObject();
+        }
+
+        private void WriteRequiredAttribute(JsonWriter writer, RequiredAttributeDescriptor requiredAttribute, JsonSerializer serializer)
+        {
+            writer.WriteStartObject();
+
+            writer.WritePropertyName(nameof(RequiredAttributeDescriptor.Name));
+            writer.WriteValue(requiredAttribute.Name);
+
+            writer.WritePropertyName(nameof(RequiredAttributeDescriptor.NameComparison));
+            writer.WriteValue(requiredAttribute.NameComparison);
+
+            writer.WritePropertyName(nameof(RequiredAttributeDescriptor.Value));
+            writer.WriteValue(requiredAttribute.Value);
+
+            writer.WritePropertyName(nameof(RequiredAttributeDescriptor.ValueComparison));
+            writer.WriteValue(requiredAttribute.ValueComparison);
+
+            writer.WritePropertyName(nameof(RequiredAttributeDescriptor.Diagnostics));
+            serializer.Serialize(writer, requiredAttribute.Diagnostics);
+
+            writer.WriteEndObject();
         }
 
         private void ReadTagMatchingRule(TagMatchingRuleDescriptorBuilder builder, JObject rule, JsonSerializer serializer)

test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Serialization/TagHelperDescriptorSerializationTest.cs

@@ -7,12 +7,66 @@ using Microsoft.AspNetCore.Mvc.Razor.Extensions;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.VisualStudio.LanguageServices.Razor.Serialization;
 using Newtonsoft.Json;
+using Newtonsoft.Json.Serialization;
 using Xunit;
 
 namespace Microsoft.VisualStudio.LanguageServices.Razor
 {
     public class TagHelperDescriptorSerializationTest
     {
+        [Fact]
+        public void TagHelperDescriptor_CanReadCamelCasedData()
+        {
+            // Arrange
+            var expectedDescriptor = CreateTagHelperDescriptor(
+                kind: TagHelperConventions.DefaultKind,
+                tagName: "tag-name",
+                typeName: "type name",
+                assemblyName: "assembly name",
+                attributes: new Action<BoundAttributeDescriptorBuilder>[]
+                {
+                    builder => builder
+                        .Name("test-attribute")
+                        .PropertyName("TestAttribute")
+                        .TypeName("string"),
+                },
+                ruleBuilders: new Action<TagMatchingRuleDescriptorBuilder>[]
+                {
+                    builder => builder
+                        .RequireAttributeDescriptor(attribute => attribute
+                            .Name("required-attribute-one")
+                            .NameComparisonMode(RequiredAttributeDescriptor.NameComparisonMode.PrefixMatch))
+                        .RequireAttributeDescriptor(attribute => attribute
+                            .Name("required-attribute-two")
+                            .NameComparisonMode(RequiredAttributeDescriptor.NameComparisonMode.FullMatch)
+                            .Value("something")
+                            .ValueComparisonMode(RequiredAttributeDescriptor.ValueComparisonMode.PrefixMatch))
+                        .RequireParentTag("parent-name")
+                        .RequireTagStructure(TagStructure.WithoutEndTag),
+                },
+                configureAction: builder =>
+                {
+                    builder.AllowChildTag("allowed-child-one");
+                    builder.AddMetadata("foo", "bar");
+                });
+            var serializerSettings = new JsonSerializerSettings()
+            {
+                ContractResolver = new CamelCasePropertyNamesContractResolver(),
+                Converters = new List<JsonConverter>
+                {
+                    TagHelperDescriptorJsonConverter.Instance,
+                    RazorDiagnosticJsonConverter.Instance,
+                }
+            };
+            var serializedDescriptor = JsonConvert.SerializeObject(expectedDescriptor, serializerSettings);
+
+            // Act
+            var descriptor = JsonConvert.DeserializeObject<TagHelperDescriptor>(serializedDescriptor, TagHelperDescriptorJsonConverter.Instance, RazorDiagnosticJsonConverter.Instance);
+
+            // Assert
+            Assert.Equal(expectedDescriptor, descriptor, TagHelperDescriptorComparer.Default);
+        }
+
         [Fact]
         public void TagHelperDescriptor_RoundTripsProperly()
         {