1 files changed, 84 insertions, 0 deletions

diff --git a/src/WixToolset.Extensibility/BasePreprocessorExtension.cs b/src/WixToolset.Extensibility/BasePreprocessorExtension.cs
new file mode 100644
index 00000000..acfcd5b9
--- /dev/null
+++ b/src/WixToolset.Extensibility/BasePreprocessorExtension.cs
@@ -0,0 +1,84 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Extensibility
+{
+    using System.Xml.Linq;
+    using WixToolset.Extensibility.Services;
+
+    /// <summary>
+    /// Base class for creating a preprocessor extension.
+    /// </summary>
+    public abstract class BasePreprocessorExtension : IPreprocessorExtension
+    {
+        /// <summary>
+        /// Context for use by the extension.
+        /// </summary>
+        protected IPreprocessContext Context { get; private set; }
+
+        /// <summary>
+        /// ParserHelper for use by the extension.
+        /// </summary>
+        protected IPreprocessHelper PreprocessHelper { get; private set; }
+
+        /// <summary>
+        /// Gets or sets the variable prefixes for the extension.
+        /// </summary>
+        /// <value>The variable prefixes for the extension.</value>
+        public string[] Prefixes { get; protected set; }
+
+        /// <summary>
+        /// Called at the beginning of the preprocessing of a source file.
+        /// </summary>
+        public virtual void PrePreprocess(IPreprocessContext context)
+        {
+            this.Context = context;
+
+            this.PreprocessHelper = context.ServiceProvider.GetService<IPreprocessHelper>();
+        }
+
+        /// <summary>
+        /// Gets the value of a variable whose prefix matches the extension.
+        /// </summary>
+        /// <param name="prefix">The prefix of the variable to be processed by the extension.</param>
+        /// <param name="name">The name of the variable.</param>
+        /// <returns>The value of the variable or null if the variable is undefined.</returns>
+        public virtual string GetVariableValue(string prefix, string name)
+        {
+            return null;
+        }
+
+        /// <summary>
+        /// Evaluates a function defined in the extension.
+        /// </summary>
+        /// <param name="prefix">The prefix of the function to be processed by the extension.</param>
+        /// <param name="function">The name of the function.</param>
+        /// <param name="args">The list of arguments.</param>
+        /// <returns>The value of the function or null if the function is not defined.</returns>
+        public virtual string EvaluateFunction(string prefix, string function, string[] args)
+        {
+            return null;
+        }
+
+        /// <summary>
+        /// Processes a pragma defined in the extension.
+        /// </summary>
+        /// <param name="sourceLineNumbers">The location of this pragma's PI.</param>
+        /// <param name="prefix">The prefix of the pragma to be processed by the extension.</param>
+        /// <param name="pragma">The name of the pragma.</param>
+        /// <param name="args">The pragma's arguments.</param>
+        /// <param name="parent">The parent node of the pragma.</param>
+        /// <returns>false if the pragma is not defined.</returns>
+        /// <comments>Don't return false for any condition except for unrecognized pragmas. Throw errors that are fatal to the compile. use core.OnMessage for warnings and messages.</comments>
+        public virtual bool ProcessPragma(string prefix, string pragma, string args, XContainer parent)
+        {
+            return false;
+        }
+
+        /// <summary>
+        /// Called at the end of the preprocessing of a source file.
+        /// </summary>
+        public virtual void PostPreprocess(XDocument document)
+        {
+        }
+    }
+}