Add compiler extension to handle platforms.

Custom actions to print EULA and validate install directories are
defined in WixUIExtension compiler extension, to handle
platform-specific custom actions referred to from `DoAction` control
events. This is the least-worst solution, given the `DoAction` approach
used in the WixUI authoring and anyone customizing a WixUI set.

2 files changed, 119 insertions, 0 deletions

diff --git a/src/ext/UI/wixext/UICompiler.cs b/src/ext/UI/wixext/UICompiler.cs
new file mode 100644
index 00000000..46b856c0
--- /dev/null
+++ b/src/ext/UI/wixext/UICompiler.cs
@@ -0,0 +1,118 @@
+// 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.UI
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Xml.Linq;
+    using WixToolset.Data;
+    using WixToolset.Data.Symbols;
+    using WixToolset.Extensibility;
+
+    /// <summary>
+    /// The decompiler for the WiX Toolset UI Extension.
+    /// </summary>
+    public sealed class UICompiler : BaseCompilerExtension
+    {
+        public override XNamespace Namespace => "http://wixtoolset.org/schemas/v4/wxs/ui";
+
+        /// <summary>
+        /// Processes an element for the Compiler.
+        /// </summary>
+        /// <param name="sourceLineNumbers">Source line number for the parent element.</param>
+        /// <param name="parentElement">Parent element of element to process.</param>
+        /// <param name="element">Element to process.</param>
+        /// <param name="contextValues">Extra information about the context in which this element is being parsed.</param>
+        public override void ParseElement(Intermediate intermediate, IntermediateSection section, XElement parentElement, XElement element, IDictionary<string, string> context)
+        {
+            switch (parentElement.Name.LocalName)
+            {
+                case "Fragment":
+                case "Module":
+                case "PatchFamily":
+                case "Package":
+                case "UI":
+                    switch (element.Name.LocalName)
+                    {
+                        case "WixUI":
+                            this.ParseWixUIElement(intermediate, section, element);
+                            break;
+                        default:
+                            this.ParseHelper.UnexpectedElement(parentElement, element);
+                            break;
+                    }
+                    break;
+                default:
+                    this.ParseHelper.UnexpectedElement(parentElement, element);
+                    break;
+            }
+        }
+
+        /// <summary>
+        /// Parses a WixUI element.
+        /// </summary>
+        private void ParseWixUIElement(Intermediate intermediate, IntermediateSection section, XElement element)
+        {
+            var sourceLineNumbers = this.ParseHelper.GetSourceLineNumbers(element);
+            string id = null;
+
+            foreach (var attrib in element.Attributes())
+            {
+                if (String.IsNullOrEmpty(attrib.Name.NamespaceName) || this.Namespace == attrib.Name.Namespace)
+                {
+                    switch (attrib.Name.LocalName)
+                    {
+                        case "Id":
+                            id = this.ParseHelper.GetAttributeIdentifierValue(sourceLineNumbers, attrib);
+                            break;
+                        default:
+                            this.ParseHelper.UnexpectedAttribute(element, attrib);
+                            break;
+                    }
+                }
+                else
+                {
+                    this.ParseHelper.ParseExtensionAttribute(this.Context.Extensions, intermediate, section, element, attrib);
+                }
+            }
+
+            if (null == id)
+            {
+                this.Messaging.Write(ErrorMessages.ExpectedAttribute(sourceLineNumbers, element.Name.LocalName, "Id"));
+            }
+            else
+            {
+                this.ParseHelper.CreateSimpleReference(section, sourceLineNumbers, SymbolDefinitions.WixUI, id);
+
+                // Because these custom actions are "scheduled" via `DoAction` control events, we have to create the
+                // custom action definitions here, so the `DoAction` references are static and the targets are
+                // dynamically created to properly reflect the platform-specific DLL and avoid having duplicate ids
+                // in the UI .wixlib.
+                var platform = this.Context.Platform == Platform.ARM64 ? "A64" : this.Context.Platform.ToString();
+                var source = $"WixUiCa_{platform}";
+
+                section.AddSymbol(new CustomActionSymbol(sourceLineNumbers, new Identifier(AccessModifier.Global, "WixUIPrintEula"))
+                {
+                    TargetType = CustomActionTargetType.Dll,
+                    Target = "PrintEula",
+                    SourceType = CustomActionSourceType.Binary,
+                    Source = source,
+                    IgnoreResult = true,
+                    ExecutionType = CustomActionExecutionType.Immediate,
+                });
+
+                section.AddSymbol(new CustomActionSymbol(sourceLineNumbers, new Identifier(AccessModifier.Global, "WixUIValidatePath"))
+                {
+                    TargetType = CustomActionTargetType.Dll,
+                    Target = "ValidatePath",
+                    SourceType = CustomActionSourceType.Binary,
+                    Source = source,
+                    IgnoreResult = true,
+                    ExecutionType = CustomActionExecutionType.Immediate,
+                });
+            }
+
+            this.ParseHelper.ParseForExtensionElements(this.Context.Extensions, intermediate, section, element);
+        }
+    }
+}
diff --git a/src/ext/UI/wixext/UIExtensionFactory.cs b/src/ext/UI/wixext/UIExtensionFactory.cs
index 141aa39f..a16a9899 100644
--- a/src/ext/UI/wixext/UIExtensionFactory.cs
+++ b/src/ext/UI/wixext/UIExtensionFactory.cs
@@ -11,6 +11,7 @@ namespace WixToolset.UI
         protected override IReadOnlyCollection<Type> ExtensionTypes => new[]
         {
             typeof(UIExtensionData),
+            typeof(UICompiler),
         };
     }
 }