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Problems with upgrading

Posted on September 17, 2010

Some of you may have noticed that the last two versions of TortoiseSVN did not always install properly if an older version was already installed. To fix the problem, all you needed to do was to run the installer again and choose "Repair" in the dialog.

Unfortunately, the next version (supposed to be 1.6.10) will have the very same problem. I'm sorry about that. But the versions after that should work fine again. That means an update from any version to version 1.6.10 or later will require a repair install!

If you want to know more about the technical details of the problem, read on. If not, just remember that all you have to do is to run the installer again and choose "Repair".

Now the technical details:

TortoiseSVN uses WiX to create the MSI installer. MSI has a built in mechanism for upgrading packages. In TortoiseSVN, we always use the major upgrade.

Msi groups files/registry entries/settings/... which are to be installed into components. Each component then contains the files/registry entries/... to install. It either installs everything that's grouped into a component or nothing. Installing only part of a component is not possible. Of course, that also applies for upgrades: either the whole component is upgraded or the whole component is left unchanged.

When upgrading, TortoiseSVN also schedules the RemoveExistingProducts action right after the InstallFinalize action. This is to make sure that even when upgrading, nothing old and unused is left lying around.

When upgrading, MSI doesn't just upgrade unconditionally but first checks whether a component actually needs upgrading. To help MSI check whether an upgrade is necessary, each component has a keypath. A keypath is usually a file or a registry key. In case of a file, MSI uses the file's version info and/or the filedate to determine whether to upgrade or not and whether the component is already installed or not. If the keypath points to a registry key, MSI can only determine whether the component is already installed or not, since a registry key has no version info and no date.

In Version 1.6.8 of TortoiseSVN, we changed the values and names of some registry keys that are used for the icon overlays. We had all those registry entries placed into a separate component, so that component only had registry entries and no files. That of course also means that the keypath of that component is a registry key.

Now here's what happened when you upgraded to version 1.6.8:

  1. MSI starts
  2. it detects the older version and all old components, also whether a component needs updating or not.
  3. MSI installs the new version. All components that need upgrading are upgraded/installed. And here's the problem: components that have a registry key as the keypath are not upgraded if that keypath already exists!
  4. After the installation of the new components is done, MSI removes all old components. Of course, the components that were upgraded are not removed since they are now newer than the one it has to remove.

As you can see, the problem with version 1.6.8 was in step 3. The old component was left in place in the upgrade. Doing a repair install forces MSI to reinstall all components in step 3, so that fixed the problem.

So I thought to fix the problem in our MSI, scheduling the RemoveExistingProducts action after the InstallValidate action was all that's needed. Which leads to the following install steps in version 1.6.9:

  1. MSI starts
  2. it detects the older version and all old components, also whether a component needs updating or not.
  3. MSI removes all components of the previous version
  4. MSI installs the new version. All components are installed since the older components were just removed. So even components that have a registry key as the keypath get properly upgraded.

So everything's fine, right? As it turned out: not so much. Unfortunately there's a problem when using components that get installed in the SxS cache. TortoiseSVN uses the C-runtime and MFC components of Visual Studio which happen to be such components, the problem described in kb905238 happened. It's a long read but worth it if you're interested. Short version: such components get removed but not installed again, so they're missing after the installation.

Of course, as with the problem with the 1.6.8 version, a repair install was all you had to do to get TortoiseSVN installed and running correctly again.

As it seems, there is no solution that really works.

The only way we can get an installer that works properly when upgrading, i.e., upgrades all components reliably even if we just change registry entries is to not use registry keys as the keypath of components.

So that's what I did now: I moved all registry entries to components that have a file as the keypath, and a file that has version info. That way, MSI detects the version and always installs the new version. And of course I've rescheduled the RemoveExistingProducts action to run after the InstallFinalize action to avoid the problem described in kb905238. So after you've installed the next version of TortoiseSVN (will be version 1.6.10), upgrading to newer versions (>= 1.6.11) should work properly again.

But of course: upgrading to 1.6.10 from any previous version will have the same problem as version 1.6.8 had. That's because the components that installed only the registry entries are installed in step 3 properly since they're now part of a component with a file path as the keypath, but then the old components are removed in step 4. And because the old components had the same registry entries as were installed in step 3, they're gone now.

To sum up: the problems we have were due to my mistake of using registry keys as keypaths for components. There's no way to fix this in MSI so that upgrades from older versions (which had this mistake built in) work. But it will work again properly for upgrades with versions that don't have that mistake anymore. That means once you have 1.6.10 installed, upgrades to higher versions will work again properly.


Ivan Zhakov suggested a solution that could have worked better: mark the registry-only components to use the parent folder as the keypath. To do this just add KeyPath='yes' to the Component element and remove KeyPath='yes' from the RegistryKey element.