mikejsavage.co.uk / blog

03 Oct 2017 / More installer junk

This is a bit of a followup to my last post about installers.

Turns out the "append /$MultiUser.InstallMode to the UninstallString" trick doesn't really work.

The problem is that when the user navigates to the folder with the uninstaller and double clicks it, as opposed to going through control panel, it will not have the command line switch and therefore will try to uninstall whatever you set as the default mode.

Coming up with a fix for this has been quite frustrating. A part of me wants to say "if the user wants to shoot themselves in the foot I can't do anything about it", but running the uninstaller manually seems pretty innocent to me, and we are the ones that lose money when our product doesn't work.

It's difficult because we are installing a plugin for some third-party software, so we have two installation folders and both of them move depending on whether it's a machine-wide or single user installation. If we only had our folder then we could just nuke whatever folder the uninstaller is in, but we need to locate the second folder too.

One suggestion was to remove the option for machine-wide installations. This would allow us to simplify the installer config (which is already pretty simple but christ I really hate putting any logic at all in these shitty crippled non-languages) but some of our clients have slow IT and requiring them to install the plugin for all of their users separately is a no go.

Another idea I tried was to look at whether the uninstaller exe was located under Program Files. It's ok but I don't think we can totally rule out users moving the installation folder somewhere else, like to another drive or something.

So I finally settled on writing an installmode.txt next to the installer. It's robust against moving the folder around and running the uninstaller directly, but the user can still go and delete the txt file if they really want to or the installer can fail to write it or etc.

I still don't like my solution because I really hate writing code that can fail. It's a huge relief when you can write a bit of code, no matter how trivial, and know that it can never go wrong. In this case I don't really have a choice because Windows doesn't provide a robust way to install software. (installers are literally just self extracting zips that also write registry keys)

It's especially upsetting because this code is going to be shipped to our non-technical customers. I dread the day when someone comes in with an insane installation problem, all of our suggestions take weeks to test and are expensive for the customer because they have to go through their outsourced IT, and then they either burn out and give up or we simply can't figure it out. Huge huge waste of time for everyone involved, and we lose the sale.

Someone noted a funny issue with the installer. If you did both a machine-wide and a single user installation at the same time, the W10 settings app would merge them together into a single entry and you couldn't choose which one to remove. They had the same name in control panel at that point too but at least both entries were there. The fix for that is to give them different registry key names. So something like HKLM\...\Uninstall\OurSoftwareAllUsers\UninstallString and HKCU\...\Uninstall\OurSoftwareCurrentUser\UninstallString. Or SHCTX\...\Uninstall\OurSoftware$MultiInstall.InstallMode. And I guess give them different DisplayNames too so you can distinguish them.