Opened 7 years ago

Closed 7 years ago

#28301 closed Bug (duplicate)

Object history is not logged for many to many fields

Reported by: Karolis Ryselis Owned by: nobody
Component: contrib.admin Version: 1.11
Severity: Normal Keywords:
Cc: Triage Stage: Unreviewed
Has patch: no Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no


Consider this

from django.db import models

class Model1(models.Model):
    title = models.CharField(max_length=20)

    def __str__(self):
        return self.title

class Model2(models.Model):
    title = models.CharField(max_length=20)
    models1 = models.ManyToManyField(to="Model1")

    def __str__(self):
        return self.title

and this

from django.contrib import admin

from .models import Model1, Model2

My test scenario:

  1. Add two Model1 items via admin
  2. Add one Model2 item via admin, choose one instance of Model1 for many-to-many field
  3. Edit the Model2 item via admin choosing both Model1 instances for many-to-many field
  4. Open history for Model2 instance
  5. "No fields changed." is in history even though we have changed one of the fields.

I guess that this could be caused by lazy evaluation of initial queryset.
Initial data is loaded from model instance using model_to_dict which calls f.value_from_object for each field. ManyToManyField implemention returns a queryset. It think it is only evaluated when object history messages are constructed, i.e., after object is saved to database, and queryset returns already saved values instead of initial values. Because of this, initial and saved data are always the same and this field never appears in changed_data.
I was able to reproduce this on 1.11.2.

Change History (1)

comment:1 by Tim Graham, 7 years ago

Resolution: duplicate
Status: newclosed

Duplicate of #27998

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