#32689: Infinite AlterField Migrations due to default callable object missmatch
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Reporter: Samuel Bishop | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 3.2
Severity: Normal | Resolution:
Keywords: infinite, | Triage Stage:
makemigrations, migrations, | Unreviewed
callable, default, field |
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Description changed by Samuel Bishop:
Old description:
> `makemigration` will generate infinite migrations if the callable path is
> miss-matched such that you end up with two discreet callable objects (I'm
> still trying to identify where exactly the migration framework is
> generating this missmatch) then the same migration is generated every
> time you run the command which results in no actual change to the
> database.
>
> In my case it's from a custom field library being used as a primary key.
>
> I was importing `from ulid.api import new as new_ulid` and setting
> `default=new_ulid`, but unless I swap to `import ulid.api.api` and set
> `default=ulid.api.api.Api.new` I just get a new identical migration
> altering the field's default value to `ulid.api.api.Api.new` every time i
> run `makemigrations`
>
> I would have expected either a clear warning detailing why my choice of
> callable object for the `default=` will cause issues, or I would have
> expected `makemigrations` to not mutate my callable like this.
New description:
`makemigration` will generate infinite migrations if the callable path is
miss-matched such that you end up with two discreet callable objects (I'm
still trying to identify where exactly the migration framework is
generating this missmatch, I can see the difference stepping through
`MigrationAutodetector.generate_altered_fields` in the debugger but I'm
not sure if the root cause is inside `generate_altered_fields`, another
method on `MigrationAutodetector` or somewhere else entirely...) then the
same migration is generated every time you run the command which results
in no actual change to the database.
In my case it's from a custom field library being used as a primary key.
I was importing `from ulid.api import new as new_ulid` and setting
`default=new_ulid`, but unless I swap to `import ulid.api.api` and set
`default=ulid.api.api.Api.new` I just get a new identical migration
altering the field's default value to `ulid.api.api.Api.new` every time i
run `makemigrations`
I would have expected either a clear warning detailing why my choice of
callable object for the `default=` will cause issues, or I would have
expected `makemigrations` to not mutate my callable like this.
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Ticket URL: <https://code.djangoproject.com/ticket/32689#comment:1>
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