sql_create generates incorrect SQL with synced database

[flakfizer]

The change between 1.6.6 to 1.7c3 in sql_create's first parameter from "app" to "app_config" is causing a bug, namely because app.get_models() returned a list, whereas app_config.get_models() returns a generator. This causes the "known_models" set to be larger than it should be.

This bug will cause invalid sql - mysql, in my case - to be generated if tables already exist, as shown in the attached reproduction app.

1) python manage.py repro # generates correct sql

CREATE TABLE `repro_app_a` (
    `id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
    `b_id` integer NOT NULL
)
;
CREATE TABLE `repro_app_b` (
    `id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
    `a_id` integer NOT NULL
)
;
ALTER TABLE `repro_app_b` ADD CONSTRAINT `a_id_refs_id_4838e71a` FOREIGN KEY (`a_id`) REFERENCES `repro_app_a` (`id`);
ALTER TABLE `repro_app_a` ADD CONSTRAINT `b_id_refs_id_b49a3179` FOREIGN KEY (`b_id`) REFERENCES `repro_app_b` (`id`);

2) python manage.py migrate
3) python manage.py repro # generates incorrect sql; the first constraint fails because table repro_app_b hasn't been created yet.

CREATE TABLE `repro_app_a` (
    `id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
    `b_id` integer NOT NULL
)
;
ALTER TABLE `repro_app_a` ADD CONSTRAINT `b_id_refs_id_b49a3179` FOREIGN KEY (`b_id`) REFERENCES `repro_app_b` (`id`);
CREATE TABLE `repro_app_b` (
    `id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
    `a_id` integer NOT NULL
)
;
ALTER TABLE `repro_app_b` ADD CONSTRAINT `a_id_refs_id_4838e71a` FOREIGN KEY (`a_id`) REFERENCES `repro_app_a` (`id`);

Fortunately, the (or, "a") fix is an easy one-liner:

django/core/management/sql.py

@@ -36 +36 @@
     # We trim models from the current app so that the sqlreset command does not
     # generate invalid SQL (leaving models out of known_models is harmless, so
     # we can be conservative).
-    app_models = app_config.get_models(include_auto_created=True)
+    app_models = set(app_config.get_models(include_auto_created=True))
     final_output = []
     tables = connection.introspection.table_names()
     known_models = set(model for model in connection.introspection.installed_models(tables) if model not in app_models)

[flakfizer]

Reproduction project

[Simon Charette]

Here's ​a working patch with tests.

[Simon Charette <charette.s@…>]

In 1e404180c1bd3535987aba96d42030daab1e9c9f:

Fixed #23379 -- Corrected a referencing issue in sql_create.

Thanks to Trac alias flakfizer for the report.

[Simon Charette <charette.s@…>]

In c32c220881ebca2be7b7bb5bec6ca4b25d1d6454:

[1.7.x] Fixed #23379 -- Corrected a referencing issue in sql_create.

Thanks to Trac alias flakfizer for the report.

Backport of 1e404180c1 from master