It seems like this is happening because in FdfParser.py, include files are processed before processing the conditional statements. I think this is being done so that all defines (even from the included files) can be accounted for before processing any conditionals. This seems to be a valid flow from pre-processing perspective, although this leaves out the use case where a file may be conditionally included.

Bob/Liming,

For now, I have fixed the issue by changing my conditional include to be the following:

In top-level FDF:
!ifdef $(BUILD_PLATFORM_XYZ)
  $(INCLUDE_XYZ_FDF)
!endif

In top-level DSC:
!ifdef $(BUILD_PLATFORM_XYZ)
  INCLUDE_XYZ_FDF = !include Platform/NVIDIA/XYZ.fdf.inc
!endif

Please suggest me if there is a batter way of working around this issue.

Thanks
Ashish
________________________________
From: Lin, Derek (HPS SW) <derek.lin2@hpe.com>
Sent: Monday, April 20, 2020 12:16 AM
To: Ashish Singhal <ashishsingha@nvidia.com>; devel@edk2.groups.io <devel@edk2.groups.io>
Subject: Re: [edk2-devel] Conditionally Include FDF File

External email: Use caution opening links or attachments

I saw this issue too.

The included file is always included no matter the condition is TRUE or FALSE.
```
!if FALSE
  !include abc.fdf
!endif
```


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