Autogenerate WXI file in WiX Build process - msbuild

Question

I have a batch file that creates a WXI file that is included in the final build process of a MSI.
If I use the "Pre-build Event" in the project setting of VS-2019 this command is always executed even if there is no need to compile the WiX project.
I tried to add
<Target Name="UpdateVersionNumber" Inputs="$(ProjectDir)..\..\..\Bin\Infile.dll" Outputs="$(ProjectDir)output.wxi">
<Exec Command=""%COMSPEC%" /c UpdateVersion.bat "$(ProjectDir)..\..\..\Bin\Infile.dll" "$(ProjectDir)$output.wxi"" />
</Target>
The batch file creates the output.wxi file depending on the DLL. The output.wxi is also part of the project.
But it is never executed. If I add BeforeTargets="Compile" it is again always executed.
I only want this batch file executed if any build is required.
In C# projects the "Pre-Build Events" are only executed when there is need for a build an any file is out of date. This isn't the case for WiX projects in VS-2019.
How to achieve that this batch file is only executed when the Infile.dll is newer than the output.wxi
Edit: The infile.dll is not created by this build process. The build process for the infile.dll is completely a separate project.

Answer 1

First, I think that there is some problems with your Infile.dll and your needs about this issue.
How to achieve that this batch file is only executed when the
Infile.dll is newer than the output.wxi
To answer this question, actually, what you did(use input and output) meets this.
If the files from the inputs node are newer than the files from outputs node, the target will be executed. See this official document.
So in your side, the Infile.dll is always built rather than up to date, and it is always newer than output.wxi which depends on it. And the batch file will generate the output.wxi based on Infile.dll. All of these cause that behavior and the target will always be executed.
BeforeTargets="Compile" just specify this target into the build process.
In C# projects the "Pre-Build Events" are only executed when there is
need for a build an any file is out of date. This isn't the case for
WiX projects in VS-2019.
There won't be any problems with this method on the surface. The real problem is that why the Infile.dll is always newer than output.wxi.
<Target Name="UpdateVersionNumber" Inputs="$(ProjectDir)..\..\..\Bin\Infile.dll" Outputs="$(ProjectDir)output.wxi" BeforeTargets="Compile">
<Exec Command=""%COMSPEC%" /c UpdateVersion.bat "$(ProjectDir)..\..\..\Bin\Infile.dll" "$(ProjectDir)$output.wxi"" />
</Target>
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First, if the Infile.dll is one of the output file of the wix project, then it can be explained clearly. Since wix project does not have incremental build feature and always
The execute order
UpdateVersionNumber(compare Infile.dll and output.wxi )--->Compare-->Build(generate the new output file Infile.dll)
For the first build time, the target will be executed and then generated the output.wxi file based on Infile.dll as expected. Then it executes the build process, it will update
Infile.dll.
However when you execute it second time, the Infile.dll is newer than output.wxi. And the target will always be executed and stuck in a loop.
In this situation, you have nothing to do.
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If Infile.dll is an content from somewhere else, you should check why the Infile.dll is always new(perhaps the wix project has a dependency relationship with the other project) rather than up-to-date.Or it could be always be updated by something else.
If Infile.dll is the output file from another type of the project, you can enter that project to check its detailed output build output log to find where the issue is.
In addition, you should check the other project very carefully and pay attention to your requirements.