Misleading error raised during system check related to ModelAdmin

[okrutny]

When comma is forgoten when defining fieldsets on ModelAdmin, wrong error is raised:

ERRORS:
<class 'fund_profiles.admin.OrganizationAdmin'>: (admin.E012) There are duplicate field(s) in 'fieldsets[0][1]'.

Code to reproduce:

class OrganizationAdmin(admin.ModelAdmin):
    
    list_display = ('name','email', 'accepted_ads','accepted_rules','accepted_handling','date_created','date_modified')
    list_filter = ('verified','accepted_ads',)
    fieldsets = (
        (_('administration'), 
         {
             'fields': ('removed')
         }),
    )

Adding comma to tuple after 'removed' fixes issue.

[Tim Graham]

Looking at the _check_fields() method in contrib/admin/checks.py, it looks like we fail to check if the nested fields inside a fieldset are a list or tuple. We can likely reuse the existing 'admin.E008' code.

[arcturusannamalai]

Attempt Django bug fix.

[arcturusannamalai]

Patch : ​https://github.com/arcturusannamalai/django/compare/ticket_24089?expand=1

[arcturusannamalai]

Replying to timgraham:

Looking at the _check_fields() method in contrib/admin/checks.py, it looks like we fail to check if the nested fields inside a fieldset are a list or tuple. We can likely reuse the existing 'admin.E008' code.

Can you please review my change, Tim?

[Tim Graham]

Please add a test case, check your against using our ​patch review checklist, and then create a pull request.

[arcturusannamalai]

Replying to timgraham:
I will update it. Thanks.

[arcturusannamalai]

I added a test, ​https://github.com/django/django/pull/3876/commits and sent a pull request.

[Claude Paroz]

Ticket is only closed when the fix is committed. And Ready for checkin should never be set by the patch author, but by a reviewer.

[Tim Graham <timograham@…>]

In b75c707943e159b80c179c538721406bbfb8b120:

Fixed #24089 -- Added check for when ModelAdmin.fieldsets[1]fields isn't a list/tuple.