Wix patch change registry value back to original value when that value is without change

Question

Can anybody explain me this behavior? Steps:

1. Install app created in Wix 4 with registry value XXX
2. Install patch A that changes registry value to YYY, works well
3. Install patch B that changes some other files but leave registry value without change, but after patch the registry value is changed back to XXX

If i change registry value in patch B (step 3) to ZZZ it again works well. I found workaround. I had to move component with that registry to separate Feature. Then it works without problem.

Wix code before workaround:

<Wix xmlns="http://wixtoolset.org/schemas/v4/wxs" xmlns:ui="http://wixtoolset.org/schemas/v4/wxs/ui">
<Package        
        Name="App"      
        Language="1033"
        Version="2.0.0.8"
        Manufacturer="Develop"
        UpgradeCode="{E0EC963D-82A9-410E-93BA-11243A15E534}"
        InstallerVersion="500"
        ProductCode="{596EF69B-157C-4C02-A566-1ED06C68B67B}">
<Media Id="1" Cabinet="media1.cab" EmbedCab="yes" />
<Property Id="WIXUI_INSTALLDIR" Value="INSTALLDIR" />

<DirectoryRef Id="APPDIR">
 <Component Id="CMP_SetReg" Guid="{F0BD26A4-D356-4F17-BF60-4AC3EE7B820A}">      
  <RegistryValue Root="HKLM" Key="SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\[ProductCode]" Action="write" Name="MyComments" Type="string" Value="XXX" KeyPath="yes"/>
 </Component>
 <Component Id="CMP_fileA" Guid="1307a453-6683-479f-a1be-f0fdc0d22cd5">
  <File Id="FILE_fileA" Source="$(var.Path)..\app.exe" KeyPath="yes" />
 </Component>      
 .
 .
</DirectoryRef>
<Feature Id="Main" Display="hidden" Level="1" ConfigurableDirectory="APPDIR" Title="Main program" >  
  <ComponentRef Id="CMP_SetReg" />
  <ComponentRef Id="CMP_fileA" />
  .
  .
</Feature>
<Feature Id="Optional" Level="1" Title="Services">
  <Feature Id="Service1" Level="1" Title="Service1" >
    <ComponentRef Id="..." />
  </Feature>
  .
  .
</Feature>
<CustomAction Id=...
.
.
</Package>
</Wix>

Patch code:

<?xml version="1.0" encoding="UTF-8"?>
<Wix xmlns="http://wixtoolset.org/schemas/v4/wxs">
  <Patch
    AllowRemoval="yes"
    Classification="Update"    
    DisplayName=".."
    Manufacturer=".."
    MoreInfoURL="..">

    <Media Id="1000" Cabinet="MyPatch.cab">
      <PatchBaseline
        Id="MyPatch"
        BaselineFile="Setup.wixpdb"
        UpdateFile="SetupNew.wixpdb" />
    </Media>

    <PatchFamily
      Id="MyPatchFamily"
      Version="2.0.0.9"      
      Supersede="yes">      
      <ComponentRef Id="..." />
      .
      .
    </PatchFamily>
  </Patch>
</Wix>

Patching files works without problem, only registry patching has this weird behavior. I dont understand why.

Answer 1

My guess is that your patch B supersedes patch A so it removes patch A from the view during the patch application, reverting the value to what was in the MSI. PatchFamilies can only grow.