App Hooks Resolution

[gavindsouza]

Description of the issue

Execution of the hooks installed on a particular site follows the alphabetical order of their naming doesn't follow a well-defined order. If an app that starts with the letter 'a''s hooks will always be executed first. There's no other control provided for priority resolution for hooks. If you want an app to override some hook with the highest priority, you'll have to change your app's name!

We discussed possible ways of handling resolution: By order of app installation on a particular site was one that seemed the most obvious quick fix for this broken system. According to this, the last installed app would have the highest priority. For hooks that pick only a single value from a mapping like override_whitelisted_methods or override_doctype_class, the last installed app that defines said hook value would be picked.

Although this adds more sanity to the system, it still feels lacking. We might need an interface for tracking hooks priority and overriding them. This should be at a site level given the timing of apps being installed on benches is immaterial and only when or how (dependency install, or explicit, etc) the app is installed on a site matters for context.

Addtional Context: #16246, #12075

[DrZoidberg09]

First of all, thank you for the explanation of how the order of hooks is sorted. This now explains why the hooks I use in my app (starting with a C) are then overwritten by ERPNext, if they also exist in the ERPNext hooks.py.

I would certainly agree that the order of installed apps would be a good fix, as this also defines the order of how migrate work.

Ultimately, it would be absolutely great to have a function that defines the order of hooks (and migrate). But having it by the order of install would be already awesome!

Looking forward to see this function! 👍

[ankush]

Can be fixed by #17869

We are going with "installed on site" order, last install wins.

We will introduce UI to change order if required in future.