[wix-users] Always installing a subset of files from within a patch

[Todd Hoatson]

Hi,
  we have a product which uses WiX to produce its installer.  The product
has a base installer for the new version, and then has patch installers for
updates to that version.

  Our process for creating the installer uses heat.exe to "harvest" the
relevant files, rather than manually specifying them.  For the base
installer, we use the -gg option to ask heat to generate the GUIDs for the
components that it identifies.  For the patch installer, this is impossible
(more on that in a moment); we ask heat to defer generation of the GUIDs to
compile time by placing '*' in the output file where the GUID would
normally be specified.  The processes look like this:

Base Installer
  heat -> candle -> light -> signtool
  -gg

Patch Installer
  "Old" Version
    heat -> candle -> light -\
    -ag                       \
                               ---> torch -> candle -> light -> pyro ->
signtool
  "New" Version               /
    heat -> candle -> light -/
    -ag

The significance of the -ag option for the GUID is that the new version
needs to be compared with the old version to determine which bits have
changed.  If heat generates different GUIDs for these two versions, then
pyro thinks that everything has changed between the two versions, and
generates a long list of errors.

Unfortunately, we had a recent mistake in our attempt to fix a bug, and
this broke backward-compatibility.  We need to revert to prior versions of
several DLLs in order to fix this bug.  The version numbers of these DLLs
are critical to the restoration of function, so we can't create new DLLs
with the prior, compatible function.

We wanted to use KeyPath="no" for these few DLLs in order to force the
installation of these DLLs without looking at the version numbers.  I tried
to use an XSLT transform on the call to heat to change the KeyPath value
from "yes" to "no" for only these few DLLs.  However, I found that we are
unable to set KeyPath="no" without also generating GUIDs immediately.

This seems like an unnecessary restriction / limitation.  Is there some way
to have a small subset of files always installed, regardless of version
number, in a patch installer?

Thanks for any help / suggestions you can offer!

-- 
Todd Hoatson
Mobile: 763-291-3312
Email:   todd.hoatson at gmail.com
www.linkedin.com/in/toddhoatson