Merge pull request #3299 from Minnozz/absorb

Track which Author/Work/Edition a duplicate has been merged into

bookwyrm/management/commands/deduplicate_book_data.py

@@ -1,13 +1,14 @@
 """ PROCEED WITH CAUTION: uses deduplication fields to permanently
 merge book data objects """
+
 from django.core.management.base import BaseCommand
 from django.db.models import Count
 from bookwyrm import models
-from bookwyrm.management.merge import merge_objects
 
 
-def dedupe_model(model):
+def dedupe_model(model, dry_run=False):
     """combine duplicate editions and update related models"""
+    print(f"deduplicating {model.__name__}:")
     fields = model._meta.get_fields()
     dedupe_fields = [
         f for f in fields if hasattr(f, "deduplication_field") and f.deduplication_field
@@ -16,30 +17,42 @@ def dedupe_model(model):
         dupes = (
             model.objects.values(field.name)
             .annotate(Count(field.name))
-            .filter(**{"%s__count__gt" % field.name: 1})
+            .filter(**{f"{field.name}__count__gt": 1})
+            .exclude(**{field.name: ""})
+            .exclude(**{f"{field.name}__isnull": True})
         )
 
         for dupe in dupes:
             value = dupe[field.name]
-            if not value or value == "":
-                continue
             print("----------")
-            print(dupe)
             objs = model.objects.filter(**{field.name: value}).order_by("id")
             canonical = objs.first()
-            print("keeping", canonical.remote_id)
+            action = "would merge" if dry_run else "merging"
+            print(
+                f"{action} into {model.__name__} {canonical.remote_id} based on {field.name} {value}:"
+            )
             for obj in objs[1:]:
-                print(obj.remote_id)
-                merge_objects(canonical, obj)
+                print(f"- {obj.remote_id}")
+                absorbed_fields = obj.merge_into(canonical, dry_run=dry_run)
+                print(f"  absorbed fields: {absorbed_fields}")
 
 
 class Command(BaseCommand):
     """deduplicate allllll the book data models"""
 
     help = "merges duplicate book data"
+
+    def add_arguments(self, parser):
+        """add the arguments for this command"""
+        parser.add_argument(
+            "--dry_run",
+            action="store_true",
+            help="don't actually merge, only print what would happen",
+        )
+
     # pylint: disable=no-self-use,unused-argument
     def handle(self, *args, **options):
         """run deduplications"""
-        dedupe_model(models.Edition)
-        dedupe_model(models.Work)
-        dedupe_model(models.Author)
+        dedupe_model(models.Edition, dry_run=options["dry_run"])
+        dedupe_model(models.Work, dry_run=options["dry_run"])
+        dedupe_model(models.Author, dry_run=options["dry_run"])

bookwyrm/management/merge.py

@@ -1,50 +0,0 @@
-from django.db.models import ManyToManyField
-
-
-def update_related(canonical, obj):
-    """update all the models with fk to the object being removed"""
-    # move related models to canonical
-    related_models = [
-        (r.remote_field.name, r.related_model) for r in canonical._meta.related_objects
-    ]
-    for (related_field, related_model) in related_models:
-        # Skip the ManyToMany fields that aren’t auto-created. These
-        # should have a corresponding OneToMany field in the model for
-        # the linking table anyway. If we update it through that model
-        # instead then we won’t lose the extra fields in the linking
-        # table.
-        related_field_obj = related_model._meta.get_field(related_field)
-        if isinstance(related_field_obj, ManyToManyField):
-            through = related_field_obj.remote_field.through
-            if not through._meta.auto_created:
-                continue
-        related_objs = related_model.objects.filter(**{related_field: obj})
-        for related_obj in related_objs:
-            print("replacing in", related_model.__name__, related_field, related_obj.id)
-            try:
-                setattr(related_obj, related_field, canonical)
-                related_obj.save()
-            except TypeError:
-                getattr(related_obj, related_field).add(canonical)
-                getattr(related_obj, related_field).remove(obj)
-
-
-def copy_data(canonical, obj):
-    """try to get the most data possible"""
-    for data_field in obj._meta.get_fields():
-        if not hasattr(data_field, "activitypub_field"):
-            continue
-        data_value = getattr(obj, data_field.name)
-        if not data_value:
-            continue
-        if not getattr(canonical, data_field.name):
-            print("setting data field", data_field.name, data_value)
-            setattr(canonical, data_field.name, data_value)
-    canonical.save()
-
-
-def merge_objects(canonical, obj):
-    copy_data(canonical, obj)
-    update_related(canonical, obj)
-    # remove the outdated entry
-    obj.delete()

bookwyrm/management/merge_command.py

@@ -1,4 +1,3 @@
-from bookwyrm.management.merge import merge_objects
 from django.core.management.base import BaseCommand
 
 
@@ -9,6 +8,11 @@ class MergeCommand(BaseCommand):
         """add the arguments for this command"""
         parser.add_argument("--canonical", type=int, required=True)
         parser.add_argument("--other", type=int, required=True)
+        parser.add_argument(
+            "--dry_run",
+            action="store_true",
+            help="don't actually merge, only print what would happen",
+        )
 
     # pylint: disable=no-self-use,unused-argument
     def handle(self, *args, **options):
@@ -26,4 +30,8 @@ class MergeCommand(BaseCommand):
             print("other book doesn’t exist!")
             return
 
-        merge_objects(canonical, other)
+        absorbed_fields = other.merge_into(canonical, dry_run=options["dry_run"])
+
+        action = "would be" if options["dry_run"] else "has been"
+        print(f"{other.remote_id} {action} merged into {canonical.remote_id}")
+        print(f"absorbed fields: {absorbed_fields}")

bookwyrm/migrations/0197_mergedauthor_mergedbook.py

@@ -0,0 +1,48 @@
+# Generated by Django 3.2.24 on 2024-02-28 21:30
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("bookwyrm", "0196_merge_pr3134_into_main"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="MergedBook",
+            fields=[
+                ("deleted_id", models.IntegerField(primary_key=True, serialize=False)),
+                (
+                    "merged_into",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.PROTECT,
+                        related_name="absorbed",
+                        to="bookwyrm.book",
+                    ),
+                ),
+            ],
+            options={
+                "abstract": False,
+            },
+        ),
+        migrations.CreateModel(
+            name="MergedAuthor",
+            fields=[
+                ("deleted_id", models.IntegerField(primary_key=True, serialize=False)),
+                (
+                    "merged_into",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.PROTECT,
+                        related_name="absorbed",
+                        to="bookwyrm.author",
+                    ),
+                ),
+            ],
+            options={
+                "abstract": False,
+            },
+        ),
+    ]

bookwyrm/models/author.py

@@ -1,4 +1,5 @@
 """ database schema for info about authors """
+
 import re
 from typing import Tuple, Any
 
@@ -10,13 +11,15 @@ from bookwyrm import activitypub
 from bookwyrm.settings import DOMAIN
 from bookwyrm.utils.db import format_trigger
 
-from .book import BookDataModel
+from .book import BookDataModel, MergedAuthor
 from . import fields
 
 
 class Author(BookDataModel):
     """basic biographic info"""
 
+    merged_model = MergedAuthor
+
     wikipedia_link = fields.CharField(
         max_length=255, blank=True, null=True, deduplication_field=True
     )

bookwyrm/models/book.py

@@ -1,13 +1,15 @@
 """ database schema for books and shelves """
+
 from itertools import chain
 import re
-from typing import Any
+from typing import Any, Dict
+from typing_extensions import Self
 
 from django.contrib.postgres.search import SearchVectorField
 from django.contrib.postgres.indexes import GinIndex
 from django.core.cache import cache
 from django.db import models, transaction
-from django.db.models import Prefetch
+from django.db.models import Prefetch, ManyToManyField
 from django.dispatch import receiver
 from django.utils.translation import gettext_lazy as _
 from model_utils import FieldTracker
@@ -108,10 +110,115 @@ class BookDataModel(ObjectMixin, BookWyrmModel):
         """only send book data updates to other bookwyrm instances"""
         super().broadcast(activity, sender, software=software, **kwargs)
 
+    def merge_into(self, canonical: Self, dry_run=False) -> Dict[str, Any]:
+        """merge this entity into another entity"""
+        if canonical.id == self.id:
+            raise ValueError(f"Cannot merge {self} into itself")
+
+        absorbed_fields = canonical.absorb_data_from(self, dry_run=dry_run)
+
+        if dry_run:
+            return absorbed_fields
+
+        canonical.save()
+
+        self.merged_model.objects.create(deleted_id=self.id, merged_into=canonical)
+
+        # move related models to canonical
+        related_models = [
+            (r.remote_field.name, r.related_model) for r in self._meta.related_objects
+        ]
+        # pylint: disable=protected-access
+        for related_field, related_model in related_models:
+            # Skip the ManyToMany fields that aren’t auto-created. These
+            # should have a corresponding OneToMany field in the model for
+            # the linking table anyway. If we update it through that model
+            # instead then we won’t lose the extra fields in the linking
+            # table.
+            # pylint: disable=protected-access
+            related_field_obj = related_model._meta.get_field(related_field)
+            if isinstance(related_field_obj, ManyToManyField):
+                through = related_field_obj.remote_field.through
+                if not through._meta.auto_created:
+                    continue
+            related_objs = related_model.objects.filter(**{related_field: self})
+            for related_obj in related_objs:
+                try:
+                    setattr(related_obj, related_field, canonical)
+                    related_obj.save()
+                except TypeError:
+                    getattr(related_obj, related_field).add(canonical)
+                    getattr(related_obj, related_field).remove(self)
+
+        self.delete()
+        return absorbed_fields
+
+    def absorb_data_from(self, other: Self, dry_run=False) -> Dict[str, Any]:
+        """fill empty fields with values from another entity"""
+        absorbed_fields = {}
+        for data_field in self._meta.get_fields():
+            if not hasattr(data_field, "activitypub_field"):
+                continue
+            canonical_value = getattr(self, data_field.name)
+            other_value = getattr(other, data_field.name)
+            if not other_value:
+                continue
+            if isinstance(data_field, fields.ArrayField):
+                if new_values := list(set(other_value) - set(canonical_value)):
+                    # append at the end (in no particular order)
+                    if not dry_run:
+                        setattr(self, data_field.name, canonical_value + new_values)
+                    absorbed_fields[data_field.name] = new_values
+            elif isinstance(data_field, fields.PartialDateField):
+                if (
+                    (not canonical_value)
+                    or (other_value.has_day and not canonical_value.has_day)
+                    or (other_value.has_month and not canonical_value.has_month)
+                ):
+                    if not dry_run:
+                        setattr(self, data_field.name, other_value)
+                    absorbed_fields[data_field.name] = other_value
+            else:
+                if not canonical_value:
+                    if not dry_run:
+                        setattr(self, data_field.name, other_value)
+                    absorbed_fields[data_field.name] = other_value
+        return absorbed_fields
+
+
+class MergedBookDataModel(models.Model):
+    """a BookDataModel instance that has been merged into another instance. kept
+    to be able to redirect old URLs"""
+
+    deleted_id = models.IntegerField(primary_key=True)
+
+    class Meta:
+        """abstract just like BookDataModel"""
+
+        abstract = True
+
+
+class MergedBook(MergedBookDataModel):
+    """an Book that has been merged into another one"""
+
+    merged_into = models.ForeignKey(
+        "Book", on_delete=models.PROTECT, related_name="absorbed"
+    )
+
+
+class MergedAuthor(MergedBookDataModel):
+    """an Author that has been merged into another one"""
+
+    merged_into = models.ForeignKey(
+        "Author", on_delete=models.PROTECT, related_name="absorbed"
+    )
+
 
 class Book(BookDataModel):
     """a generic book, which can mean either an edition or a work"""
 
+    merged_model = MergedBook
+
     connector = models.ForeignKey("Connector", on_delete=models.PROTECT, null=True)
 
     # book/work metadata
@@ -192,9 +299,13 @@ class Book(BookDataModel):
         """properties of this edition, as a string"""
         items = [
             self.physical_format if hasattr(self, "physical_format") else None,
-            f"{self.languages[0]} language"
-            if self.languages and self.languages[0] and self.languages[0] != "English"
-            else None,
+            (
+                f"{self.languages[0]} language"
+                if self.languages
+                and self.languages[0]
+                and self.languages[0] != "English"
+                else None
+            ),
             str(self.published_date.year) if self.published_date else None,
             ", ".join(self.publishers) if hasattr(self, "publishers") else None,
         ]

bookwyrm/tests/test_merge.py

@@ -0,0 +1,97 @@
+"""test merging Authors, Works and Editions"""
+
+from django.test import TestCase
+from django.test.client import Client
+
+from bookwyrm import models
+
+
+class MergeBookDataModel(TestCase):
+    """test merging of subclasses of BookDataModel"""
+
+    @classmethod
+    def setUpTestData(cls):  # pylint: disable=invalid-name
+        """shared data"""
+        models.SiteSettings.objects.create()
+
+        cls.jrr_tolkien = models.Author.objects.create(
+            name="J.R.R. Tolkien",
+            aliases=["JRR Tolkien", "Tolkien"],
+            bio="This guy wrote about hobbits and stuff.",
+            openlibrary_key="OL26320A",
+            isni="0000000121441970",
+        )
+        cls.jrr_tolkien_2 = models.Author.objects.create(
+            name="J.R.R. Tolkien",
+            aliases=["JRR Tolkien", "John Ronald Reuel Tolkien"],
+            openlibrary_key="OL26320A",
+            isni="wrong",
+            wikidata="Q892",
+        )
+        cls.jrr_tolkien_2_id = cls.jrr_tolkien_2.id
+
+        # perform merges
+        cls.jrr_tolkien_absorbed_fields = cls.jrr_tolkien_2.merge_into(cls.jrr_tolkien)
+
+    def test_merged_author(self):
+        """verify merged author after merge"""
+        self.assertEqual(self.jrr_tolkien_2.id, None, msg="duplicate should be deleted")
+
+    def test_canonical_author(self):
+        """verify canonical author data after merge"""
+
+        self.assertFalse(
+            self.jrr_tolkien.id is None, msg="canonical should not be deleted"
+        )
+
+        # identical in canonical and duplicate; should be unchanged
+        self.assertEqual(self.jrr_tolkien.name, "J.R.R. Tolkien")
+        self.assertEqual(self.jrr_tolkien.openlibrary_key, "OL26320A")
+
+        # present in canonical and absent in duplicate; should be unchanged
+        self.assertEqual(
+            self.jrr_tolkien.bio, "This guy wrote about hobbits and stuff."
+        )
+
+        # absent in canonical and present in duplicate; should be absorbed
+        self.assertEqual(self.jrr_tolkien.wikidata, "Q892")
+
+        # scalar value that is different in canonical and duplicate; should be unchanged
+        self.assertEqual(self.jrr_tolkien.isni, "0000000121441970")
+
+        # set value with both matching and non-matching elements; should be the
+        # union of canonical and duplicate
+        self.assertEqual(
+            self.jrr_tolkien.aliases,
+            [
+                "JRR Tolkien",
+                "Tolkien",
+                "John Ronald Reuel Tolkien",
+            ],
+        )
+
+    def test_merged_author_redirect(self):
+        """a web request for a merged author should redirect to the canonical author"""
+        client = Client()
+        response = client.get(
+            f"/author/{self.jrr_tolkien_2_id}/s/jrr-tolkien", follow=True
+        )
+        self.assertEqual(response.redirect_chain, [(self.jrr_tolkien.local_path, 301)])
+
+    def test_merged_author_activitypub(self):
+        """an activitypub request for a merged author should return the data for
+        the canonical author (including the canonical id)"""
+        client = Client(HTTP_ACCEPT="application/json")
+        response = client.get(f"/author/{self.jrr_tolkien_2_id}")
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(response.json(), self.jrr_tolkien.to_activity())
+
+    def test_absorbed_fields(self):
+        """reported absorbed_fields should be accurate for --dry_run"""
+        self.assertEqual(
+            self.jrr_tolkien_absorbed_fields,
+            {
+                "aliases": ["John Ronald Reuel Tolkien"],
+                "wikidata": "Q892",
+            },
+        )

bookwyrm/utils/partial_date.py

@@ -67,6 +67,14 @@ class PartialDate(datetime):
         # current_timezone and default_timezone.
         return cls.from_datetime(datetime(year, month, day, tzinfo=_westmost_tz))
 
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, PartialDate):
+            return NotImplemented
+        return self.partial_isoformat() == other.partial_isoformat()
+
+    def __repr__(self) -> str:
+        return f"<{self.__class__.__name__} object: {self.partial_isoformat()}>"
+
 
 class MonthParts(PartialDate):
     """a date bound into month precision"""

bookwyrm/views/author.py

@@ -1,4 +1,5 @@
 """ the good people stuff! the authors! """
+
 from django.contrib.auth.decorators import login_required, permission_required
 from django.core.paginator import Paginator
 from django.shortcuts import get_object_or_404, redirect
@@ -11,7 +12,11 @@ from bookwyrm import forms, models
 from bookwyrm.activitypub import ActivitypubResponse
 from bookwyrm.connectors import connector_manager
 from bookwyrm.settings import PAGE_LENGTH
-from bookwyrm.views.helpers import is_api_request, maybe_redirect_local_path
+from bookwyrm.views.helpers import (
+    is_api_request,
+    get_mergeable_object_or_404,
+    maybe_redirect_local_path,
+)
 
 
 # pylint: disable= no-self-use
@@ -21,7 +26,7 @@ class Author(View):
     # pylint: disable=unused-argument
     def get(self, request, author_id, slug=None):
         """landing page for an author"""
-        author = get_object_or_404(models.Author, id=author_id)
+        author = get_mergeable_object_or_404(models.Author, id=author_id)
 
         if is_api_request(request):
             return ActivitypubResponse(author.to_activity())
@@ -56,13 +61,13 @@ class EditAuthor(View):
 
     def get(self, request, author_id):
         """info about a book"""
-        author = get_object_or_404(models.Author, id=author_id)
+        author = get_mergeable_object_or_404(models.Author, id=author_id)
         data = {"author": author, "form": forms.AuthorForm(instance=author)}
         return TemplateResponse(request, "author/edit_author.html", data)
 
     def post(self, request, author_id):
         """edit a author cool"""
-        author = get_object_or_404(models.Author, id=author_id)
+        author = get_mergeable_object_or_404(models.Author, id=author_id)
 
         form = forms.AuthorForm(request.POST, request.FILES, instance=author)
         if not form.is_valid():
@@ -82,7 +87,7 @@ def update_author_from_remote(request, author_id, connector_identifier):
     connector = connector_manager.load_connector(
         get_object_or_404(models.Connector, identifier=connector_identifier)
     )
-    author = get_object_or_404(models.Author, id=author_id)
+    author = get_mergeable_object_or_404(models.Author, id=author_id)
 
     connector.update_author_from_remote(author)
 

bookwyrm/views/books/books.py

@@ -1,4 +1,5 @@
 """ the good stuff! the books! """
+
 from uuid import uuid4
 
 from django.contrib.auth.decorators import login_required, permission_required
@@ -15,7 +16,11 @@ from bookwyrm.activitypub import ActivitypubResponse
 from bookwyrm.connectors import connector_manager, ConnectorException
 from bookwyrm.connectors.abstract_connector import get_image
 from bookwyrm.settings import PAGE_LENGTH
-from bookwyrm.views.helpers import is_api_request, maybe_redirect_local_path
+from bookwyrm.views.helpers import (
+    is_api_request,
+    maybe_redirect_local_path,
+    get_mergeable_object_or_404,
+)
 
 
 # pylint: disable=no-self-use
@@ -40,7 +45,11 @@ class Book(View):
         # table, so they never have clashing IDs
         book = (
             models.Edition.viewer_aware_objects(request.user)
-            .filter(Q(id=book_id) | Q(parent_work__id=book_id))
+            .filter(
+                Q(id=book_id)
+                | Q(parent_work__id=book_id)
+                | Q(absorbed__deleted_id=book_id)
+            )
             .order_by("-edition_rank")
             .select_related("parent_work")
             .prefetch_related("authors", "file_links")
@@ -82,11 +91,13 @@ class Book(View):
             "book": book,
             "statuses": paginated.get_page(request.GET.get("page")),
             "review_count": reviews.count(),
-            "ratings": reviews.filter(
-                Q(content__isnull=True) | Q(content="")
-            ).select_related("user")
-            if not user_statuses
-            else None,
+            "ratings": (
+                reviews.filter(Q(content__isnull=True) | Q(content="")).select_related(
+                    "user"
+                )
+                if not user_statuses
+                else None
+            ),
             "rating": reviews.aggregate(Avg("rating"))["rating__avg"],
             "lists": lists,
             "update_error": kwargs.get("update_error", False),
@@ -130,7 +141,7 @@ class Book(View):
 @require_POST
 def upload_cover(request, book_id):
     """upload a new cover"""
-    book = get_object_or_404(models.Edition, id=book_id)
+    book = get_mergeable_object_or_404(models.Edition, id=book_id)
     book.last_edited_by = request.user
 
     url = request.POST.get("cover-url")
@@ -168,7 +179,7 @@ def set_cover_from_url(url):
 @permission_required("bookwyrm.edit_book", raise_exception=True)
 def add_description(request, book_id):
     """upload a new cover"""
-    book = get_object_or_404(models.Edition, id=book_id)
+    book = get_mergeable_object_or_404(models.Edition, id=book_id)
 
     description = request.POST.get("description")
 
@@ -199,7 +210,9 @@ def update_book_from_remote(request, book_id, connector_identifier):
     connector = connector_manager.load_connector(
         get_object_or_404(models.Connector, identifier=connector_identifier)
     )
-    book = get_object_or_404(models.Book.objects.select_subclasses(), id=book_id)
+    book = get_mergeable_object_or_404(
+        models.Book.objects.select_subclasses(), id=book_id
+    )
 
     try:
         connector.update_book_from_remote(book)

bookwyrm/views/books/edit_book.py

@@ -1,4 +1,5 @@
 """ the good stuff! the books! """
+
 from re import sub, findall
 from django.contrib.auth.decorators import login_required, permission_required
 from django.contrib.postgres.search import SearchRank, SearchVector
@@ -18,9 +19,10 @@ from bookwyrm.utils.isni import (
     build_author_from_isni,
     augment_author_metadata,
 )
-from bookwyrm.views.helpers import get_edition
+from bookwyrm.views.helpers import get_edition, get_mergeable_object_or_404
 from .books import set_cover_from_url
 
+
 # pylint: disable=no-self-use
 @method_decorator(login_required, name="dispatch")
 @method_decorator(
@@ -42,7 +44,7 @@ class EditBook(View):
 
     def post(self, request, book_id):
         """edit a book cool"""
-        book = get_object_or_404(models.Edition, id=book_id)
+        book = get_mergeable_object_or_404(models.Edition, id=book_id)
 
         form = forms.EditionForm(request.POST, request.FILES, instance=book)
 
@@ -130,7 +132,7 @@ class CreateBook(View):
 
         with transaction.atomic():
             book = form.save(request)
-            parent_work = get_object_or_404(models.Work, id=parent_work_id)
+            parent_work = get_mergeable_object_or_404(models.Work, id=parent_work_id)
             book.parent_work = parent_work
 
             if authors:
@@ -295,7 +297,7 @@ class ConfirmEditBook(View):
             if not book.parent_work:
                 work_match = request.POST.get("parent_work")
                 if work_match and work_match != "0":
-                    work = get_object_or_404(models.Work, id=work_match)
+                    work = get_mergeable_object_or_404(models.Work, id=work_match)
                 else:
                     work = models.Work.objects.create(title=form.cleaned_data["title"])
                     work.authors.set(book.authors.all())

bookwyrm/views/books/editions.py

@@ -1,4 +1,5 @@
 """ the good stuff! the books! """
+
 from functools import reduce
 import operator
 
@@ -7,7 +8,7 @@ from django.core.cache import cache as django_cache
 from django.core.paginator import Paginator
 from django.db import transaction
 from django.db.models import Q
-from django.shortcuts import get_object_or_404, redirect
+from django.shortcuts import redirect
 from django.template.response import TemplateResponse
 from django.views import View
 from django.views.decorators.http import require_POST
@@ -15,7 +16,7 @@ from django.views.decorators.http import require_POST
 from bookwyrm import forms, models
 from bookwyrm.activitypub import ActivitypubResponse
 from bookwyrm.settings import PAGE_LENGTH
-from bookwyrm.views.helpers import is_api_request
+from bookwyrm.views.helpers import is_api_request, get_mergeable_object_or_404
 
 
 # pylint: disable=no-self-use
@@ -24,7 +25,7 @@ class Editions(View):
 
     def get(self, request, book_id):
         """list of editions of a book"""
-        work = get_object_or_404(models.Work, id=book_id)
+        work = get_mergeable_object_or_404(models.Work, id=book_id)
 
         if is_api_request(request):
             return ActivitypubResponse(work.to_edition_list(**request.GET))
@@ -83,7 +84,7 @@ class Editions(View):
 def switch_edition(request):
     """switch your copy of a book to a different edition"""
     edition_id = request.POST.get("edition")
-    new_edition = get_object_or_404(models.Edition, id=edition_id)
+    new_edition = get_mergeable_object_or_404(models.Edition, id=edition_id)
     shelfbooks = models.ShelfBook.objects.filter(
         book__parent_work=new_edition.parent_work, shelf__user=request.user
     )

bookwyrm/views/books/links.py

@@ -1,4 +1,5 @@
 """ the good stuff! the books! """
+
 from django.contrib.auth.decorators import login_required, permission_required
 from django.db import transaction
 from django.shortcuts import get_object_or_404, redirect
@@ -8,6 +9,7 @@ from django.utils.decorators import method_decorator
 from django.views.decorators.http import require_POST
 
 from bookwyrm import forms, models
+from bookwyrm.views.helpers import get_mergeable_object_or_404
 
 
 # pylint: disable=no-self-use
@@ -20,7 +22,7 @@ class BookFileLinks(View):
 
     def get(self, request, book_id):
         """view links"""
-        book = get_object_or_404(models.Edition, id=book_id)
+        book = get_mergeable_object_or_404(models.Edition, id=book_id)
         annotated_links = get_annotated_links(book)
 
         data = {"book": book, "links": annotated_links}
@@ -36,7 +38,7 @@ class BookFileLinks(View):
 
         # this form shouldn't ever really get here, since it's just a dropdown
         # get the data again rather than redirecting
-        book = get_object_or_404(models.Edition, id=book_id)
+        book = get_mergeable_object_or_404(models.Edition, id=book_id)
         annotated_links = get_annotated_links(book, form=form)
 
         data = {"book": book, "links": annotated_links}
@@ -75,7 +77,7 @@ class AddFileLink(View):
 
     def get(self, request, book_id):
         """Create link form"""
-        book = get_object_or_404(models.Edition, id=book_id)
+        book = get_mergeable_object_or_404(models.Edition, id=book_id)
         data = {
             "file_link_form": forms.FileLinkForm(),
             "book": book,
@@ -85,7 +87,9 @@ class AddFileLink(View):
     @transaction.atomic
     def post(self, request, book_id, link_id=None):
         """Add a link to a copy of the book you can read"""
-        book = get_object_or_404(models.Book.objects.select_subclasses(), id=book_id)
+        book = get_mergeable_object_or_404(
+            models.Book.objects.select_subclasses(), id=book_id
+        )
         link = get_object_or_404(models.FileLink, id=link_id) if link_id else None
         form = forms.FileLinkForm(request.POST, instance=link)
         if not form.is_valid():

bookwyrm/views/books/series.py

@@ -1,10 +1,10 @@
 """ books belonging to the same series """
+
 from sys import float_info
 from django.views import View
-from django.shortcuts import get_object_or_404
 from django.template.response import TemplateResponse
 
-from bookwyrm.views.helpers import is_api_request
+from bookwyrm.views.helpers import is_api_request, get_mergeable_object_or_404
 from bookwyrm import models
 
 
@@ -27,7 +27,7 @@ class BookSeriesBy(View):
         if is_api_request(request):
             pass
 
-        author = get_object_or_404(models.Author, id=author_id)
+        author = get_mergeable_object_or_404(models.Author, id=author_id)
 
         results = models.Edition.objects.filter(authors=author, series=series_name)
 
@@ -56,9 +56,11 @@ class BookSeriesBy(View):
             sorted(numbered_books, key=sort_by_series)
             + sorted(
                 dated_books,
-                key=lambda book: book.first_published_date
-                if book.first_published_date
-                else book.published_date,
+                key=lambda book: (
+                    book.first_published_date
+                    if book.first_published_date
+                    else book.published_date
+                ),
             )
             + sorted(
                 unsortable_books,

bookwyrm/views/get_started.py

@@ -1,4 +1,5 @@
 """ Helping new users figure out the lay of the land """
+
 import re
 
 from django.contrib.auth.decorators import login_required
@@ -13,6 +14,7 @@ from django.views import View
 from bookwyrm import book_search, forms, models
 from bookwyrm.settings import INSTANCE_ACTOR_USERNAME
 from bookwyrm.suggested_users import suggested_users
+from bookwyrm.views.helpers import get_mergeable_object_or_404
 from .preferences.edit_user import save_user_form
 
 
@@ -80,8 +82,8 @@ class GetStartedBooks(View):
             for k, v in request.POST.items()
             if re.match(r"\d+", k) and re.match(r"\d+", v)
         ]
-        for (book_id, shelf_id) in shelve_actions:
-            book = get_object_or_404(models.Edition, id=book_id)
+        for book_id, shelf_id in shelve_actions:
+            book = get_mergeable_object_or_404(models.Edition, id=book_id)
             shelf = get_object_or_404(models.Shelf, id=shelf_id)
 
             models.ShelfBook.objects.create(book=book, shelf=shelf, user=request.user)

bookwyrm/views/helpers.py

@@ -1,4 +1,5 @@
 """ helper functions used in various views """
+
 import re
 from datetime import datetime, timedelta
 import dateutil.parser
@@ -8,7 +9,7 @@ from dateutil.parser import ParserError
 from requests import HTTPError
 from django.db.models import Q
 from django.conf import settings as django_settings
-from django.shortcuts import redirect
+from django.shortcuts import redirect, _get_queryset
 from django.http import Http404
 from django.utils import translation
 
@@ -232,3 +233,19 @@ def redirect_to_referer(request, *args, **kwargs):
 
     # if not, use the args passed you'd normally pass to redirect()
     return redirect(*args or "/", **kwargs)
+
+
+# pylint: disable=redefined-builtin,invalid-name
+def get_mergeable_object_or_404(klass, id):
+    """variant of get_object_or_404 that also redirects if id has been merged
+    into another object"""
+    queryset = _get_queryset(klass)
+    try:
+        return queryset.get(pk=id)
+    except queryset.model.DoesNotExist:
+        try:
+            return queryset.get(absorbed__deleted_id=id)
+        except queryset.model.DoesNotExist:
+            pass
+
+        raise Http404(f"No {queryset.model} with ID {id} exists")

bookwyrm/views/reading.py

@@ -1,4 +1,5 @@
 """ the good stuff! the books! """
+
 import logging
 from django.contrib.auth.decorators import login_required
 from django.core.cache import cache
@@ -11,6 +12,7 @@ from django.views import View
 from django.views.decorators.http import require_POST
 
 from bookwyrm import forms, models
+from bookwyrm.views.helpers import get_mergeable_object_or_404
 from bookwyrm.views.shelf.shelf_actions import unshelve
 from .status import CreateStatus
 from .helpers import get_edition, handle_reading_status, is_api_request
@@ -130,7 +132,7 @@ class ReadThrough(View):
 
     def get(self, request, book_id, readthrough_id=None):
         """standalone form in case of errors"""
-        book = get_object_or_404(models.Edition, id=book_id)
+        book = get_mergeable_object_or_404(models.Edition, id=book_id)
         form = forms.ReadThroughForm()
         data = {"form": form, "book": book}
         if readthrough_id:
@@ -152,7 +154,7 @@ class ReadThrough(View):
         )
         form = forms.ReadThroughForm(request.POST)
         if not form.is_valid():
-            book = get_object_or_404(models.Edition, id=book_id)
+            book = get_mergeable_object_or_404(models.Edition, id=book_id)
             data = {"form": form, "book": book}
             if request.POST.get("id"):
                 data["readthrough"] = get_object_or_404(

bookwyrm/views/shelf/shelf_actions.py

@@ -1,11 +1,12 @@
 """ shelf views """
+
 from django.db import IntegrityError, transaction
 from django.contrib.auth.decorators import login_required
 from django.shortcuts import get_object_or_404, redirect
 from django.views.decorators.http import require_POST
 
 from bookwyrm import forms, models
-from bookwyrm.views.helpers import redirect_to_referer
+from bookwyrm.views.helpers import redirect_to_referer, get_mergeable_object_or_404
 
 
 @login_required
@@ -36,7 +37,7 @@ def delete_shelf(request, shelf_id):
 @transaction.atomic
 def shelve(request):
     """put a book on a user's shelf"""
-    book = get_object_or_404(models.Edition, id=request.POST.get("book"))
+    book = get_mergeable_object_or_404(models.Edition, id=request.POST.get("book"))
     desired_shelf = get_object_or_404(
         request.user.shelf_set, identifier=request.POST.get("shelf")
     )
@@ -97,7 +98,7 @@ def shelve(request):
 def unshelve(request, book_id=False):
     """remove a book from a user's shelf"""
     identity = book_id if book_id else request.POST.get("book")
-    book = get_object_or_404(models.Edition, id=identity)
+    book = get_mergeable_object_or_404(models.Edition, id=identity)
     shelf_book = get_object_or_404(
         models.ShelfBook, book=book, shelf__id=request.POST["shelf"]
     )

bookwyrm/views/status.py

@@ -1,4 +1,5 @@
 """ what are we here for if not for posting """
+
 import re
 import logging
 
@@ -19,6 +20,7 @@ from markdown import markdown
 from bookwyrm import forms, models
 from bookwyrm.models.report import DELETE_ITEM
 from bookwyrm.utils import regex, sanitizer
+from bookwyrm.views.helpers import get_mergeable_object_or_404
 from .helpers import handle_remote_webfinger, is_api_request
 from .helpers import load_date_in_user_tz_as_utc, redirect_to_referer
 
@@ -52,7 +54,7 @@ class CreateStatus(View):
 
     def get(self, request, status_type):  # pylint: disable=unused-argument
         """compose view (...not used?)"""
-        book = get_object_or_404(models.Edition, id=request.GET.get("book"))
+        book = get_mergeable_object_or_404(models.Edition, id=request.GET.get("book"))
         data = {"book": book}
         return TemplateResponse(request, "compose.html", data)
 
@@ -98,7 +100,7 @@ class CreateStatus(View):
         # inspect the text for user tags
         content = status.content
         mentions = find_mentions(request.user, content)
-        for (_, mention_user) in mentions.items():
+        for _, mention_user in mentions.items():
             # add them to status mentions fk
             status.mention_users.add(mention_user)
         content = format_mentions(content, mentions)
@@ -109,7 +111,7 @@ class CreateStatus(View):
 
         # inspect the text for hashtags
         hashtags = find_or_create_hashtags(content)
-        for (_, mention_hashtag) in hashtags.items():
+        for _, mention_hashtag in hashtags.items():
             # add them to status mentions fk
             status.mention_hashtags.add(mention_hashtag)
         content = format_hashtags(content, hashtags)
@@ -140,7 +142,7 @@ class CreateStatus(View):
 
 def format_mentions(content, mentions):
     """Detect @mentions and make them links"""
-    for (mention_text, mention_user) in mentions.items():
+    for mention_text, mention_user in mentions.items():
         # turn the mention into a link
         content = re.sub(
             rf"(?<!/)\B{mention_text}\b(?!@)",
@@ -152,7 +154,7 @@ def format_mentions(content, mentions):
 
 def format_hashtags(content, hashtags):
     """Detect #hashtags and make them links"""
-    for (mention_text, mention_hashtag) in hashtags.items():
+    for mention_text, mention_hashtag in hashtags.items():
         # turn the mention into a link
         content = re.sub(
             rf"(?<!/)\B{mention_text}\b(?!@)",