Introduce new namespace and solve duplicate key issue

src/main/scala/com/typesafe/sbt/packager/windows/Keys.scala

@@ -17,4 +17,6 @@ trait WindowsKeys {
   val wixFile = TaskKey[File]("wix-file", "The WIX XML file to package with.")
   val candleOptions = SettingKey[Seq[String]]("candle-options", "Options to pass to the candle.exe program.")
   val lightOptions = SettingKey[Seq[String]]("light-options", "Options to pass to the light.exe program.")
+  val wixMajorVersion = SettingKey[Int]("wix-major-version", "Major version of the Wix suit.")
+
 }

src/main/scala/com/typesafe/sbt/packager/windows/WindowsPlugin.scala

@@ -57,6 +57,8 @@ object WindowsPlugin extends AutoPlugin {
       "-cultures:en-us"),
     wixProductId := WixHelper.makeGUID,
     wixProductUpgradeId := WixHelper.makeGUID,
+    wixMajorVersion := 4,
+
     maintainer in Windows <<= maintainer,
     packageSummary in Windows <<= packageSummary,
     packageDescription in Windows <<= packageDescription,
@@ -88,8 +90,9 @@ object WindowsPlugin extends AutoPlugin {
     wixProductConfig <<= (name in Windows, wixPackageInfo, wixFeatures, wixProductLicense) map { (name, product, features, license) =>
       WixHelper.makeWixProductConfig(name, product, features, license)
     },
-    wixConfig <<= (name in Windows, wixPackageInfo, wixProductConfig) map { (name, product, nested) =>
-      WixHelper.makeWixConfig(name, product, nested)
+    wixConfig <<= (name in Windows, wixPackageInfo, wixMajorVersion, wixProductConfig) map { (name, product, wmv, nested) =>
+      val namespaceDefinitions = WixHelper.getNameSpaceDefinitions(wmv)
+      WixHelper.makeWixConfig(name, product, namespaceDefinitions, nested)
     },
     wixConfig in Windows <<= wixConfig,
     wixProductConfig in Windows <<= wixProductConfig,

src/main/scala/com/typesafe/sbt/packager/windows/WixHelper.scala

@@ -36,6 +36,12 @@ case class ComponentFile(
   source: String,
   editable: Boolean = false
 ) extends FeatureComponent
+/** Define wix namespace definitions, that depend on the major version of Wix tools **/
+case class NamespaceDefinitions(
+  majorVersionNumber: Int,
+  namespace: String,
+  utilExtension: String
+)
 /**
  * Will add the directory to the windows path.  NOTE: Only one of these
  * per MSI.
@@ -209,9 +215,10 @@ object WixHelper {
   def makeWixConfig(
     name: String, // package name
     product: WindowsProductInfo,
+    namespaceDefinitions: NamespaceDefinitions,
     rest: xml.Node
   ): xml.Node = {
-    <Wix xmlns='http://schemas.microsoft.com/wix/2006/wi' xmlns:util='http://schemas.microsoft.com/wix/UtilExtension'>
+    <Wix xmlns={ namespaceDefinitions.namespace } xmlns:util={ namespaceDefinitions.utilExtension }>
       <Product Id={ product.id } Name={ product.title } Language='1033' Version={ product.version } Manufacturer={ product.maintainer } UpgradeCode={ product.upgradeId }>
         <Package Description={ product.description } Comments={ product.comments } Manufacturer={ product.maintainer } InstallScope={ product.installScope } InstallerVersion={ product.installerVersion } Compressed={ if (product.compressed) "yes" else "no" }/>
         <Media Id='1' Cabinet={ cleanStringForId(name.toLowerCase).takeRight(66) + ".cab" } EmbedCab='yes'/>
@@ -220,6 +227,25 @@ object WixHelper {
     </Wix>
   }
 
+  /**
+   * Wix namespace changed from major version 3 to 4.
+   * TODO: Not sure if schema of 2006 is compatible with major versions < 3
+   */
+  def getNameSpaceDefinitions(majorVersion: Int): NamespaceDefinitions = {
+    if (majorVersion <= 3)
+      NamespaceDefinitions(
+        majorVersion,
+        namespace = "http://schemas.microsoft.com/wix/2006/wi",
+        utilExtension = "http://schemas.microsoft.com/wix/UtilExtension"
+      )
+    else
+      NamespaceDefinitions(
+        majorVersion,
+        namespace = "http://wixtoolset.org/schemas/v4/wxs",
+        utilExtension = "http://wixtoolset.org/schemas/v4/wxs/util"
+      )
+  }
+
   /**
    * Modifies a string to be Wix ID friendly by removing all the bad
    * characters and replacing with _.  Also limits the width to 70 (rather than