Move the merging code from deduplicate code to common module

That way it can be used in a new command to merge individual items.

bookwyrm/management/commands/deduplicate_book_data.py

@@ -1,50 +1,9 @@
 """ 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, ManyToManyField
+from django.db.models import Count
 from bookwyrm import models
-
-
-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()
+from bookwyrm.management.merge import merge_objects
 
 
 def dedupe_model(model):
@@ -71,10 +30,7 @@ def dedupe_model(model):
             print("keeping", canonical.remote_id)
             for obj in objs[1:]:
                 print(obj.remote_id)
-                copy_data(canonical, obj)
-                update_related(canonical, obj)
-                # remove the outdated entry
-                obj.delete()
+                merge_objects(canonical, obj)
 
 
 class Command(BaseCommand):

bookwyrm/management/merge.py

@@ -0,0 +1,50 @@
+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()