Wix: Merge Module with multiple wxs files - wix

Question

So, I am trying to create a merge module where I have multiple wxs files. I thought that everything was OK since the build of my project succeeded. Later, I realized that the path used in Source attribute for one of the secondary wxs files was completely wrong but the compiler didn't give the following error:
The system cannot find the file '..\..\release_area\WrongPath\Component2.dll'.
In the secondary wxs file, I added a DirectoryRef element referencing the folder AssemblyFolder in the main wxs file to create the reference between the two files.
Main wxs file:
<Module Id="MyModule" Language="1033" Version="1.0.0.0">
<Package InstallerVersion="200" Platform="x86"/>
<Directory Id="TARGETDIR" Name="SourceDir">
<Directory Id="AssemblyFolder">
<Component Id="Component1.dll">
<File Id="Component1.dll" Name="Component1.dll"
KeyPath="yes" Assembly=".net"
Source="..\..\release_area\Comp\Component1.dll" />
</Component>
</Directory>
</Directory>
</Module>
Secondary wxs file:
<Fragment>
<DirectoryRef Id="AssemblyFolder">
<Component Id="Component2.dll">
<File Id="Component2.dll" Name="Component2.dll"
KeyPath="yes" Assembly=".net"
Source="..\..\release_area\WrongPath\Component2.dll" />
</Component>
</DirectoryRef>
</Fragment>
Just to clarify: To test, I copied my <Component Id="Component2.dll"> directly in the main wxs and I got the error: The system cannot find the file '..\..\release_area\WrongPath\Component2.dll'.
So, my guess is that the reference between the secondary wxs file and the main wxs file is completely wrong and that's why the compiler doesn't validate the file path but I cannot figure out what is the problem.

Answer 1

The issue isn't in the compiler (candle.exe). Candle.exe creates the separate "sections" (Module and Fragment are both "sections"). It is the linker (light.exe) that is responsible for pulling it all together. Light.exe starts at the "entry section" (Product, Module or Patch) and follows the references down from there. Since you don't have a reference from your Main.wxs to your Secondary.wxs, the stuff in the Secondary.wxs is never pulled in. To resolve this just add:
<ComponentRef Id="Component2.dll"/>
somewhere under your Module element (I usually put them at the end). If you get lots of Components then ComponentGroup and ComponentGroupRef becomes useful.