Define schema help model for elements.

#5

src/LanguageServer.Common/Help/ElementHelp.cs

@@ -0,0 +1,41 @@
+using Newtonsoft.Json;
+using System;
+using System.Collections.Generic;
+
+namespace MSBuildProjectTools.LanguageServer.Help
+{
+    /// <summary>
+    ///     Help information for an MSBuild element.
+    /// </summary>
+    public class ElementHelp
+    {
+        /// <summary>
+        ///     The property description.
+        /// </summary>
+        [JsonProperty("description")]
+        public string Description { get; set; }
+
+        /// <summary>
+        ///     Help link for the element (if any).
+        /// </summary>
+        [JsonProperty("help")]
+        public string HelpLink { get; set; }
+
+        /// <summary>
+        ///     Load help property help from JSON.
+        /// </summary>
+        /// <param name="json">
+        ///     A <see cref="JsonReader"/> representing the JSON ("PropertyName": { "description": "PropertyDescription" }).
+        /// </param>
+        /// <returns>
+        ///     A sorted dictionary of help items, keyed by property name.
+        /// </returns>
+        public static SortedDictionary<string, ElementHelp> FromJson(JsonReader json)
+        {
+            if (json == null)
+                throw new ArgumentNullException(nameof(json));
+
+            return new JsonSerializer().Deserialize<SortedDictionary<string, ElementHelp>>(json);
+        }
+    }
+}

src/LanguageServer.SemanticModel.MSBuild/MSBuildSchemaHelp.cs

@@ -25,6 +25,9 @@ static MSBuildSchemaHelp()
             HelpDirectory = new DirectoryInfo(
                 Path.Combine(extensionDirectory, "help")
             );
+            ElementHelpFile = new FileInfo(
+                Path.Combine(HelpDirectory.FullName, "elements.json")
+            );
             PropertyHelpFile = new FileInfo(
                 Path.Combine(HelpDirectory.FullName, "properties.json")
             );
@@ -35,6 +38,12 @@ static MSBuildSchemaHelp()
                 Path.Combine(HelpDirectory.FullName, "tasks.json")
             );
 
+            using (StreamReader input = ElementHelpFile.OpenText())
+            using (JsonTextReader json = new JsonTextReader(input))
+            {
+                ElementHelp = Help.ElementHelp.FromJson(json);
+            }
+
             using (StreamReader input = PropertyHelpFile.OpenText())
             using (JsonTextReader json = new JsonTextReader(input))
             {
@@ -55,6 +64,11 @@ static MSBuildSchemaHelp()
             }
         }
 
+        /// <summary>
+        ///     Help for MSBuild elements.
+        /// </summary>
+        static SortedDictionary<string, ElementHelp> ElementHelp { get; }
+
         /// <summary>
         ///     Help for MSBuild properties.
         /// </summary>
@@ -80,6 +94,11 @@ static MSBuildSchemaHelp()
         /// </summary>
         public static DirectoryInfo HelpDirectory { get; }
 
+        /// <summary>
+        ///     The file that stores help for well-known MSBuild elements.
+        /// </summary>
+        public static FileInfo ElementHelpFile { get; }
+
         /// <summary>
         ///     The file that stores help for well-known MSBuild properties.
         /// </summary>
@@ -159,6 +178,27 @@ public static string ForElement(string elementName)
             return null;
         }
 
+        /// <summary>
+        ///     Get a help link (if available) for the specified element.
+        /// </summary>
+        /// <param name="elementName">
+        ///     The element name.
+        /// </param>
+        /// <returns>
+        ///     The element help link, or <c>null</c> if no link is available for it.
+        /// </returns>
+        public static string HelpLinkForElement(string elementName)
+        {
+            if (String.IsNullOrWhiteSpace(elementName))
+                throw new ArgumentException("Argument cannot be null, empty, or entirely composed of whitespace: 'elementName'.", nameof(elementName));
+
+            string helpKey = elementName;
+            if (ElementHelp.TryGetValue(helpKey, out ElementHelp help))
+                return help.HelpLink;
+
+            return null;
+        }
+
         /// <summary>
         ///     Get help content for the specified attribute.
         /// </summary>