Default of [] for postgres array field results in migration application failure.

[Matthew Schinckel]

Creating an ArrayField with a default of [] results in an error when attempting to run the migration:

django.db.utils.DataError: missing dimension value

It seems that the literal [] is being sent through to the database, rather than the postgres-speak for an empty array: '{}'

It's the same issue as seen elsewhere on the internet when dealing with postgres arrays:

​https://github.com/ecometrica/django-dbarray/issues/2

[Matthew Schinckel]

Oh, it was an undimensioned array: not sure if that's important.

[Matthew Schinckel]

In ArrayField.get_prep_value(self,value), adding:

    if value == '[]':
        value = '{}'

makes it work as expected.

[Marc Tamlyn]

PR: ​https://github.com/django/django/pull/2925

Not sure why I am getting a string from the migration runner, seems a little strange. Nonetheless it works now.

[Marc Tamlyn <marc.tamlyn@…>]

In ef9f109013adc6e140c1a71d874aa88e893657b7:

Fixed #22962 -- Default values for ArrayField with migrations.

Fields normally try to force the default value to a string. As
translatable strings are not valid default values for ArrayField, we can
remove this behaviour which was causing issues with some migrations.

Thanks to @schinckel for the report.

[Markus Holtermann <info@…>]

In b06935a486e633e9732bce2bc5f796eb437b2531:

Refs #22962 -- Made test case use non-conflicting table names

[Markus Holtermann <info@…>]

In 45d93baf518218c39b70fbc1eb35e9b53f66cf98:

[1.8.x] Refs #22962 -- Made test case use non-conflicting table names

Backport of b06935a486e633e9732bce2bc5f796eb437b2531 from master

[Doug Whiteley]

This is happening again.

django.db.utils.DataError: malformed array literal: ""
DETAIL:  Array value must start with "{" or dimension information.

Checked on 1.10 and 1.11rc1.

[Matthew Schinckel]

I'm not sure it's exactly the same issue: it's a different error message, for one.

[Doug Whiteley]

Reopened in error