Opened 8 months ago

Last modified 6 months ago

#23034 new New feature

Add migrations support for adding ManyToMany "through" model

Reported by: lorinkoz@… Owned by: nobody
Component: Migrations Version: 1.7-rc-1
Severity: Normal Keywords:
Cc: Triage Stage: Someday/Maybe
Has patch: no Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description

Adding a "through" model on a ManyToMany field make "makemigrations" fail with an explicit error stating that it is not possible. I have worked it around by renaming the field, creating the migration (so as to make Django believe it's a new field) and then renaming the field back to the original name and creating another migration (which is correctly acknowledged by Django as a simple "renaming"). I understand the implications of adding a through model from the migrations perspective, but maybe a more friendly output could be achieved. Is it even possible to create some sort of interaction, like when you create a field with not null and no default value, so as to ask the user if they want to destroy/create a new field??

Change History (2)

comment:1 Changed 7 months ago by timo

  • Needs documentation unset
  • Needs tests unset
  • Patch needs improvement unset
  • Summary changed from Migrations fail with modified ManyToMany "through" model to Add migrations support for adding ManyToMany "through" model
  • Triage Stage changed from Unreviewed to Accepted
  • Type changed from Uncategorized to New feature

As Andrew noted in #22476, "as the error message says, you cannot alter an M2M without a through model into one with a through model, at least not in the current system." I'm not sure how feasible it will be to add support for thits, but tentatively accepting.

comment:2 Changed 6 months ago by andrewgodwin

  • Triage Stage changed from Accepted to Someday/Maybe

Triaging this to "someday/maybe". It would be nice, but it's a complex thing to add.

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