When updating, download & verify new package before uninstalling

[spongbros]

Currently, performing an upgrade of a package runs an uninstallation before downloading the updated files. It is possible for the download to fail or for the checksum to not match, leaving no copy of the package installed and, potentially, no way to reinstall it. Ideally, the update package should be downloaded and verified before the uninstallation process begins.

[quincunx]

The current behaviour is unfortunate but an old version is not remove at all.

E.g. I've vim installed - which gets an update every 1-2 days. Every single installed/updated version is still on my system, see the directory %USERPROFILE%\scoop\apps\vim:

8.0.1765
8.0.1766
8.0.1772
8.0.1774
8.0.1780
8.0.1787
8.0.1789
8.0.1795
current

current is a link to the latest installed version (8.0.1795).

So all it would need is to detect a failed update and act accordingly. Maybe uninstalling (of shims) and removing the current link is not required at all - as it will be overwritten by the new version (if it's successful).

https://github.com/lukesampson/scoop/wiki/The-'Current'-Version-Alias

[r15ch13]

When a download or hash check fails it will leave an empty directory behind. If we remove it and simply run scoop reset <app> it should be fixed.

[gitolicious]

Maybe reset could check if current links to an empty folder and fix it automatically.
Also, are post_install steps performed and are all shims put back in place with the reset command? Otherwise the app will end up in a messed up state.

[r15ch13]

@gitolicious no, reset doesn't run post_intall, it's only for fixing shortcuts, shims, and environment variables. See scoop-reset.ps1

[gitolicious]

Well, then unfortunately your suggestion is only valid for very basic manifests. I see two solutions here:

1. Perform download to cache before uninstallation -> should prevent most internet connection related problems
2. Perform self-healing by re-installing the old version after a failed update -> brings the user back to a usable state
   Probably both can solutions can be put in place in parallel.

[gitolicious]

PR for solution 1 in #2343

[r15ch13]

reset is mostly for switching between package versions like python and python27, which have the same executables. Running post_install is not suited for this command.

[ghost]

Just experienced this in ScoopInstaller/Extras#1269 but it is not the first time. Considering how many issues come up when you search for is:issue "hash check fail" on the main scoop repo, not to mention the buckets, this would be VERY nice to have.

[ghost]

Coming back to the number of issues raised. I think a lot less "hash check fail" issues would be raised if the app wasn't left in an uninstalled state, saving time fixing hashes.