Enable upgrades in MSI.

Fixes #2228.

tools/msvs/msi/nodemsi.wixproj

@@ -16,12 +16,12 @@
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|x86' ">
     <OutputPath>..\..\..\$(Configuration)\</OutputPath>
     <IntermediateOutputPath>obj\$(Configuration)\</IntermediateOutputPath>
-    <DefineConstants>Debug;ProductVersion=$(NodeVersion);NPMSourceDir=..\..\..\deps\npm\</DefineConstants>
+    <DefineConstants>Debug;ProductVersion=$(NodeVersion);ProductId=$(NodeProductId);NPMSourceDir=..\..\..\deps\npm\</DefineConstants>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|x86' ">
     <OutputPath>..\..\..\$(Configuration)\</OutputPath>
     <IntermediateOutputPath>obj\$(Configuration)\</IntermediateOutputPath>
-    <DefineConstants>Debug;ProductVersion=$(NodeVersion);NPMSourceDir=..\..\..\deps\npm\</DefineConstants>
+    <DefineConstants>Debug;ProductVersion=$(NodeVersion);ProductId=$(NodeProductId);NPMSourceDir=..\..\..\deps\npm\</DefineConstants>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="product.wxs" />

tools/msvs/msi/product.wxs

@@ -4,7 +4,7 @@
   <?define repoDir="$(var.ProjectDir)..\..\..\" ?>
   <?define sourcedir="$(var.repoDir)\$(var.Configuration)\" ?>
 
-  <Product Id="cc6c176e-e26c-48ec-8970-f58bd1d046cf"
+  <Product Id="$(var.ProductId)"
            Name="node.js"
            Language="1033"
            Version="$(var.ProductVersion)"
@@ -14,6 +14,9 @@
     <Package InstallerVersion="200" Compressed="yes" Platform="x86" />
 
     <Media Id="1" Cabinet="media1.cab" EmbedCab="yes" />
+
+    <MajorUpgrade AllowSameVersionUpgrades="yes" 
+                  DowngradeErrorMessage="A later version of node.js is already installed. Setup will now exit." />
     
     <Directory Id="TARGETDIR" Name="SourceDir">
       <Directory Id="ProgramFilesFolder">

vcbuild.bat

@@ -89,7 +89,9 @@ python "%~dp0tools\getnodeversion.py" > "%temp%\node_version.txt"
 if not errorlevel 0 echo Cannot determine current version of node.js & goto exit
 for /F "tokens=*" %%i in (%temp%\node_version.txt) do set NODE_VERSION=%%i
 heat dir deps\npm -var var.NPMSourceDir -dr NodeModulesFolder -cg NPMFiles -gg -template fragment -nologo -out npm.wxs
-msbuild "%~dp0tools\msvs\msi\nodemsi.sln" /t:Clean,Build /p:Configuration=%config% /p:NodeVersion=%NODE_VERSION% /clp:NoSummary;NoItemAndPropertyList;Verbosity=minimal /nologo
+uuidgen > "%temp%\node_product_id.txt"
+set /p NODE_PRODUCT_ID=<"%temp%\node_product_id.txt"
+msbuild "%~dp0tools\msvs\msi\nodemsi.sln" /t:Clean,Build /p:Configuration=%config% /p:NodeVersion=%NODE_VERSION% /p:NodeProductId=%NODE_PRODUCT_ID% /clp:NoSummary;NoItemAndPropertyList;Verbosity=minimal /nologo
 if errorlevel 1 goto exit
 
 if defined nosign goto run