Support inline admins

[merwok]

Problem Statement

Not sure if this is a bug or feature: inline admins can't be displayed in the admin form view.

Describe the solution you'd like

Port PR #315 to add "inline_admin_formsets" in context to make them available.

Describe alternatives you've considered

Additional context

[pallavg]

Good evening - Was wondering if there was any progress on this enhancement. We are using this app in our project. It works very well, but are not able to see the changes in the admin view for inline admins. It is not a big deal but since this ticket is open, was curious . Thank you.

[rossmechanic]

Haven't look at it – but if you want to take a stab at it, I'd be happy to look at your pr @pallavg

[hatiq-ssi]

Was this enhancement added? I am using inline on my admin form but it is not visible in the history.

[frobert]

would be really great to have. Are there any workarounds or temp solutions?

[tomH01]

My company uses simple history as well. I found a solution to display the correct inlines in the admin (sketched below).
If you are interested in the solution, I would obtain approval from my company to contribute the solution.
However, the solutions has some workarounds that would be nice to be replaced firstly:

• Always Save Inlines: All inlines have to be saved whenever the parent model is saved (solved by AlwaysSaveForm in the inline class). It would be better to handle this directly within django-simple-history.
• Save Order: The standard Django save order has to be used (Parent first, Children afterward)

Solution Overview

Prerequisites:

• Inlines are always within a ForeignKey relationship (Child points to Parent)
• HistoricalModels deliver a version field history_id
• When a Parent is changed a new historical parent record with a history_id is created
• When modifying the inlines of a Parent, only the affected Children will have a new historical record

Implementation:

1. Always Save Inlines: Use an AlwaysSaveForm to ensure all Children are saved whenever the Parent is saved.
2. Mapping: For each foreign key of a Child add a new field in the historical child model to create a mapping to the Parent history_id:

• Distiguish by history_type of Child: "No change", "Created (+)", "Deleted (-)", "Modified (~)"
• If "No change" or "Created (+)" or "Modified (~)" then add latest Parent history_id
• Else change nothing
  
• Display the Inlines: Display the inlines with parts of Add support for admin inlines #315 while filtering them by their mapping field