Wix: Using KeyPath on Components, Directories, Files, Registry, etc, etc
installation, windows-installer, wix
Solution
In general, you should base your decision on the main idea of `KeyPath` option. From MSDN:
This value points to a file or folder belonging to the component that the installer uses to detect the component.
So, if you author 1 file per component, you won't face the situation when you accidentally deleted a file and repair didn't bring it back. If you author N files per component, you'll anyway either select one of them to be a `KeyPath` (and WiX docs encourage you to do this explicitly), or you add an extra registry entry and let it be the `KeyPath`.
Back to your questions:
If I have an empty directory that installer needs to create should I set KeyPath="yes" on Directory or
Directory element doesn't have a `KeyPath` attribute.
If a File has KeyPath="yes" in a file-per-component scenario, is it necessary or good practice to set it on its parent Component?
No, basically, this doesn't make sense. If a Component has `KeyPath="yes"`, then the directory this component is installed to becomes a key path. When you set it on a File explicitly, then obviously the file is a key path.
I read somewhere that instead of setting KeyPath on a File, one should use a Registry key for each File and set KeyPath="yes" on Registry element...Is that really true/necessary?
This sounds like nonsense. Again, base on the general need for `KeyPath` - detect the component. Why do you need an extra registry entry to detect whether a file is there on a file system? It might make sense for N files per component scenario, when you author 1 registry entry per component (that is N files), and let Windows Installer judge by that registry entry, whether the component is considered "not broken".
UPDATE: You don't have to introduce a registry entry just to serve as a key path to help installer tracking an empty folder. It is enough if you add `KeyPath='yes'` to the parent component.
Don't complicate things. Windows Installer is quite complex as it is. :) Hope this helps.
Problem
After reading this answer on "one file per component" approach when using WiX, I was curious to find out what are the best practices when using `KeyPath` attribute on other elements including `Component`, `Directory`, `Registry` etc, etc. I am interested in any general suggestion, but here are a couple of concrete questions: - If I have an empty directory that installer needs to create should I set `KeyPath="yes"` on `Directory` or its parent `Component`? What if it is not empty? - If a File has `KeyPath="yes"` in a file-per-component scenario, is it necessary or good practice to set it on its parent Component? - I read somewhere that instead of setting `KeyPath` on a File, one should use a Registry key for each File and set `KeyPath="yes"` on Registry element...Is that really true/necessary? Thanks! Edit #1 - Clarification re: `Directory` I was aware of Directory not having KeyPath, but was not explicit/detailed in my question. Mainly, I was curious about the usage of KeyPath on a Component when an empty directory has to be created. I am seeing that KeyPath="yes" is in such case being set on the parent Component. But is that enough for the installer to detect/repair missing empty folder? Or should it be used along with registry entry? Example snippet: ``` <Directory Id="LOGS" Name="Logs"> <Component Id="LogsDir" Guid="*" KeyPath="yes"> <CreateFolder Directory="LOGS" /> </Component> </Directory> ```