Uninstalling a mod should also prompt user about uninstalling its unused dependencies

[Dazpoet]

It was mentioned in the CKAN thread over at the forums that it would be pretty kickass if CKAN upon removing a mod also removed dependencies which no other mod depends on.

Say we e.g. install FerramAerospaceResearch which depends on ModuleManager and ModularFlightIntegrator. After that we install HotRockets which depends on ModuleManager and SmokeScreen.

We now have the following list of installed mods:

- FerramAerospaceResearch
- ModuleManager
- ModularFlightIntegrator
- HotRockets
- SmokeScreen

Currently if we uninstall FerramAerospaceResearch we'll end up with the following list of installed mods:

- ModuleManager
- ModularFlightIntegrator
- HotRockets
- SmokeScreen

While it seems more logical that we should end up with:

- ModuleManager
- HotRockets
- SmokeScreen

The reason for prompting the user about these things would be that e.g. uninstalling KarbonitePlus doesn't necessarily mean I want to uninstall Karbonite.

I think e.g. apt already works this way so it would seem a logical direction for CKAN to go in.

[dbent]

Arch Linux's package manager, pacman, (and presumably others) does this by keeping a bit in its database to indicate if a package was installed explicitly by the user. Then when a package is uninstalled, it will also automatically remove any dependencies that were 1) not installed explicitly and 2) are not needed by any other package.

pacman also includes functionality to:

• Flip the explicit bit on/off
• Control whether or not automatic removal is used
• Perform the removal recursively (so if Mod A depends on Mod B which depends on Mod C, removing Mod A will automatically remove Mod B and Mod C, so long as neither were installed explicitly and nothing depends on them)
• List "orphan" packages, which are packages with the explicit bit off but are currently not used by any other package.

By default I would suggest that automatic removal be used and be recursive. I would also suggest that since "explicitness" isn't currently stored that when first populating the bit, all top level packages (packages that are not dependencies for any other package) be marked as explicitly installed and all other packages be marked as being installed implicitly. This isn't perfect but good enough so long as users can toggle the explicit bit themselves.

[pjf]

+1 on dbent's comments here.

[Dazpoet]

I like any kind of solution that makes this system work, think it would be awesome :)

[Dazpoet]

Implementing this might accidentally provide a solution to #589 ? Or am I misunderstanding how this marking of mods explicitly installed and not would be added?

[pjf]

@Dazpoet : Aye, this is essentially #589 with an implementation strategy. :)

[HebaruSan]

Implemented in #2753.