Moving Wagtail pages in a migration

Question

I'm restructuring my Wagtail app to remove an IndexPage that only has a single item in it, and moving that item to be a child of the current IndexPage's parent.

basically moving from this:

Page--| |--IndexPage--| |--ChildPages (there's only ever 1 of these)

to this:

Page--| |--ChildPage

I've made the changes to the models so that this structure is used for creating new content and fixed the relevant views to point to the ChildPage directly. But now I want to migrate the current data to the new structure and I'm not sure how to go about it... Ideally this would be done in a migration so that we would not have to do any of this manipulation by hand.

Is there a way to move these ChildPage's up the tree programmatically during a migration?

Answer 1

Unfortunately there's a hard limitation that (probably) rules out the possibility of doing page tree adjustments within migrations: tree operations such as inserting, moving and deleting pages are implemented as methods on the Page model, and within a migration you only have access to a 'dummy' version of that model, which only gives you access to the database fields and basic ORM methods, not those custom methods.

(You might be able to work around this by putting from wagtail.wagtailcore.models import Page in your migration and using that instead of the standard Page = apps.get_model("wagtailcore", "Page") approach, but I wouldn't recommend that - it's liable to break if the migration is run at a point in the migration sequence where the Page model is still being built up and doesn't match the 'real' state of the model.)

Instead, I'd suggest writing a Django management command to do the tree manipulation - within a management command it is safe to import the Page model from wagtailcore, as well as your specific page models. Page provides a method move(target, pos) which works as per the Treebeard API - the code for moving your child pages might look something like:

from myapp.models import IndexPage

# ...
for index_page in IndexPage.objects.all():
    for child_page in index_page.get_children():
        child_page.move(index_page, 'right')
    index_page.delete()