"Conflicting migrations detected" CommandError due to replacement Migration being removed

[Daniel Hahler]

I am getting the following error:

CommandError: Conflicting migrations detected; multiple leaf nodes in the migration graph: (0002_initial_models, 0XXX_merge_20170628_1435 in myapp).
To fix them run 'python manage.py makemigrations --merge'

Running the command results in No conflicts detected to merge. however.

0002_initial_models is not actually a leaf node, but 0003_initial_data depends on it.
0003_initial_data however is removed, since it replaces 0XXX_merge_20170628_1435, which is not applied yet and therefore also does not show up in showmigrations?!
(it gets removed in ​https://github.com/django/django/blob/a6756195c1a11eee10c16c96fe95d52e22e1d9ba/django/db/migrations/graph.py#L252)

I think 0003_initial_data should still show up in showmigrations, but with some indication that it replaces other migrations.
That would happen in case it wasn't removed as a leaf node in ​https://github.com/django/django/blob/a6756195c1a11eee10c16c96fe95d52e22e1d9ba/django/core/management/commands/showmigrations.py#L82-L83.

[Tim Graham]

Can you provide more explicit steps to reproduce the problematic situation?

[Daniel Hahler]

Not currently.

I think a fix might be to move over the replaces from the node that gets replaced, and/or only to replace up to the parent that got applied in ​https://github.com/django/django/blob/a6756195c1a11eee10c16c96fe95d52e22e1d9ba/django/db/migrations/graph.py#L243-L245.

[Tim Graham]

Tentatively accepting. Might be difficult to proceed without steps to reproduce unless you plan to offer a patch.

[Windson yang]

I need more details to fix this bug.