Remove a GUID="" component installed with WiX

Question

I've messed up my WiX-based installer on multiple servers so that it no longer removes files or components (or even other features) during an uninstall. The MSI log shows that PreviouslyPinned=1 on all the components that won't uninstall.

I don't have anything fancy going on like using SharedDll count or even shared components among different installers.

I think I've tracked it down to a particular revision of my WiX code. I did a couple of stupid things. I (unintentionally) created an unmanaged component with a blank Guid

<Component Id="file.ext" Guid="">
    <File .../>
<Component>

and I also changed another component's file location and Id (but not it's Guid). All components present in earlier revisions show PreviouslyPinned=1 and won't uninstall, and new components added after this revision install/uninstall correctly.

How can I get my installer back to normal and remove these previously pinned components?

Answer 1

Windows Installer actually supports the concept of a blank GUID. It means "install, but don't register the component": http://msdn.microsoft.com/en-us/library/aa368007(VS.85).aspx (ComponentId entry explains what happens with a null GUID).

I just tested with WIX and it appears to respect a blank GUID entry (i.e. no guid is auto-generated). Remember the 1:1 rule between absolute path / key path and GUID:

• If you change the GUID, a new absolute path should be used for the component key path.
• If you change the absolute path (for example by renaming a file, or moving it), you should change the GUID.

In summary, the GUID reference-counts the component's install key path, not the file - which may move, but then the file has a new identity via a new GUID (think of two files with the same name in different folders - they are different files, different identities).

Cleaning up messed up GUID reference counting can be a bit messy. I find that if I can change the file name that effectively removes the problem. I also generate a new guid and hence break the link to old guid's ref count. You can also rename the installation folder (which would ideally mean that all component GUIDs should be changed as well). The RemoveFile table concept can be used to remove files on install and / or uninstall that have not been registered as components (for example generated files).

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UPDATE (Aug, 2018): Just want to add that you should be careful renaming your dlls or exe files if your application relies on LoadLibrary / LoadLibraryEx or whatever similar constructs that "hard code" file names - that are to be loaded - deep in the source code.