id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
37230	ModelAdmin.list_display: AttributeError when a __ lookup path ends in a relation field (regression from #36926)	RobKuipers		"Since #36926, `list_display` entries using `__` lookup syntax to traverse related fields (documented at https://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.list_display) raise `AttributeError` when the *final* segment of the path is itself a relation field (ForeignKey/OneToOneField), rather than a scalar field.

This worked correctly before #36926 and is not limited to any unusual setup — any `related__fk_field` entry regresses.

=== Minimal reproduction ===

{{{#!python
class Publisher(models.Model):
    name = models.CharField(max_length=100)

class Book(models.Model):
    title = models.CharField(max_length=100)
    publisher = models.ForeignKey(Publisher, on_delete=models.CASCADE)

class Author(models.Model):
    name = models.CharField(max_length=100)
    book = models.ForeignKey(Book, on_delete=models.CASCADE)

@admin.register(Author)
class AuthorAdmin(admin.ModelAdmin):
    list_display = [""name"", ""book__publisher""]
}}}

Visiting the `Author` changelist with at least one row raises:

{{{
AttributeError: 'Author' object has no attribute 'publisher'
}}}

=== Root cause ===

#36926 added this to `lookup_field()` in `django/contrib/admin/utils.py`,
specifically to let `display_for_field()` recognize `BooleanField`s reached
via a `__` path so it can render the boolean icon:

{{{#!python
                    # The final field is needed for displaying boolean icons.
                    if LOOKUP_SEP in name:
                        f = get_fields_from_path(opts.model, name)[-1]
}}}

This sets `f` unconditionally whenever the path contains `LOOKUP_SEP`, not only when the terminal field is a `BooleanField`. Previously, `f` stayed
`None` for this whole branch (the ""method, property, related field, or callable"" fallback), and `items_for_result()` in `django/contrib/admin/templatetags/admin_list.py` used the already correctly-traversed `value` via `display_for_value()`.

Now that `f` is non-`None`, `items_for_result()` takes a different branch that assumes `f` is a field belonging to `result` directly:

{{{#!python
            else:
                if isinstance(f.remote_field, models.ManyToOneRel):
                    field_val = getattr(result, f.name)
}}}

That assumption holds for the normal case (`list_display = [""publisher""]` where `publisher` really is a field on the model being rendered), but not for the `__`-traversal case, where `f` is a field on the *related* model several hops down the path — `result` (an `Author`) has no `publisher` attribute; `result.book` does.

=== Suggested fix direction ===

Scope the new `f` assignment to its stated purpose — only set it when the terminal field is actually a `BooleanField` — rather than for every `LOOKUP_SEP`-containing path:

{{{#!python
                    if LOOKUP_SEP in name:
                        final_field = get_fields_from_path(opts.model, name)[-1]
                        if isinstance(final_field, models.BooleanField):
                            f = final_field
}}}

This preserves the boolean-icon feature #36926 added while restoring the pre-6.1 (and documented) behavior for `__` paths ending in any other field
type, including relations.

I have not attempted a full patch/tests — that's a little out of my league I'm afraid.
"	Bug	new	contrib.admin	dev	Release blocker			RobKuipers	Unreviewed	0	0	0	0	0	0