Refs #24928 -- Added introspection support for PostgreSQL JSONField

[claudep]

No description provided.

[adamchainz]

Could maybe be documented in the django.contrib.postgres docs? inspectdb is typically run on day one of a project, they might not be aware they need to edit INSTALLED_APPS first to get JSONField support.

[claudep]

You're right in that people inspecting a legacy db may not know in advance that a contrib.postgres supported field is present. I'm afraid that putting a note inside django.contrib.postgres docs may not be very helpful in that regard.
What about a hint inside the inspectdb output, so instead of 'This field type is a guess.', people read 'This field type is a guess. You may try adding 'django.contrib.postgresql' in your INSTALLED_APPS setting.? This would however also favor a bit contrib.postgresql over third-party packages.

[adamchainz]

"This field is a guess. It may be supported by contrib or third party apps." ?

[timgraham]

Usually we camel case assertions to match the unittest style. Maybe assertFieldsInModel (considering field_outputs is a list).

[timgraham]

This could be indented inside the if conn.vendor to avoid a redundant check.

[claudep]

Did you meant inside if conn.connection? We want to update data_types_reverse whatever conn.connection is.

[timgraham]

if conn.vendor == 'postgresql':
    conn.introspection.data_types_reverse.update({
    ...
    if conn.connection is not None:

(register_type_handlers() also checks conn.vendor == 'postgresql' so that avoids that same check for the non-postgres case)

[claudep]

Ack!

[timgraham]

trailing comma

[timgraham]

test_jsonfield looks good to me (since this is InspectDBTests, _introspection seems redundant).

[timgraham]

My inclination is to omit this change as part of this commit. For new users, I think it will raise more questions than answers. I think it's probably better to have some more specific instructions in docs/howto/legacy-databases.txt about it. Considering there's no stable API for it, I'd be surprised if there are any third-party apps that are adding introspection for their fields but if there are some examples, I'd be interested to know about it.

[timgraham]

chop blank line?

[claudep]

Tentative doc addition.

[timgraham]

Maybe wait to add the doc until "several" fields are actually supported?

[claudep]

Adding RangeFields support is straightforward, the patch is already in good shape.

[timgraham]

Double the backticks or use

:mod:`django.contrib.postgres`

[timgraham]

It merits a release note for django.contrib.postgres also:

* ``inspectdb`` can now introspect  ``JSONField`` (``django.contrib.postgres``
  must be in ``INSTALLED_APPS``).

[claudep]

See #9049 for RangeField.