First InlineModelAdmin not displaying "Add Another" link when related_name='+'

[jamesp]

The first InlineModelAdmin displayed in a ModelAdmin subclass does not show the "Add Another" link.

The admin HTML code that gets generated for inlines appears to be inconsistent (for example, the generated HTML has id="id_MAX_FORMS" while the inlines jQuery is looking for #id_-MAX_FORMS).

[Carl Meyer]

Using the following models.py and admin.py on trunk Django, I get "add another" links for both book and subject when I add/edit an author.

models.py:

from django.db import models


class Author(models.Model):
    name = models.CharField(max_length=100)


class Subject(models.Model):
    name = models.CharField(max_length=100)
    author = models.ForeignKey(Author)


class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.ForeignKey(Author)

admin.py:

from django.contrib import admin

from .models import Book, Author, Subject


class BookInline(admin.TabularInline):
    model = Book


class SubjectInline(admin.TabularInline):
    model = Subject


admin.site.register(Subject)
admin.site.register(Book)
admin.site.register(Author, inlines=[BookInline, SubjectInline])

[jamesp]

I got your results with the code above and realized I needed to provide more information about my models.

If you set up the ForeignKeys with related_name='+', then you get the behavior I described:

from django.db import models


class Author(models.Model):
    name = models.CharField(max_length=100)


class Subject(models.Model):
    name = models.CharField(max_length=100, related_name='+')
    author = models.ForeignKey(Author)


class Book(models.Model):
    title = models.CharField(max_length=100, related_name='+')
    author = models.ForeignKey(Author)

[jamesp]

"Add another" link missing with related_name='+' in ForeignKey

[Carl Meyer]

Verified. Note that related_name actually should be on the FKs, not the CharFields ;-) Thanks for the report!

[Carl Meyer]

#13407 was a recent bug in the same area, likely related.

[jamesp]

My god, I am a mess. You're right, it should be on the ForeignKeys.

I need some damn sleep. :P

[jamesp]

Tests to pass for admin inlines with related_name='+'

[jamesp]

Potential fix for this bug

[jamesp]

What's occurring here is that related_name='+' causes the form prefix to be blank. This causes issues for inlines because the first item comes through with an entirely blank prefix. This behavior breaks the admin Javascript.

The attached patch passes the regression tests, as best I can tell.

[Carl Meyer]

In [16860]:

Fixed #16838 -- Corrected broken add-another inline JS in admin with related_name="+". Thanks jamesp for report and patch.