Models with cyclic foreign keys and ENUM-typed fields can't be synced in Postgres

[francofrizzo]

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Bug Description

In PostgreSQL, when there is a circular dependency between models (following foreign keys) and at least some model in the database has an ENUM-typed property, calls to sequelize.sync() will fail, as the enum type is attempted to be created twice.

This bug seems to have been introduced in v6.20.0, when support for cyclic foreign keys was added. The implementation synchronizes the models twice, first to create the tables, and then to create the foreign keys. Both runs are attempting to create the types for the ENUM-typed fields, which is not an idempotent operation.

Reproducible Example

Here is the link to the SSCCE for this issue: https://github.com/francofrizzo/sequelize-sscce-cyclic-associations

What do you expect to happen?

Models should be correctly synced when sequelize.sync() is called.

What is actually happening?

A SequelizeDatabaseError is thrown, indicating that type "enum_<model>_<field>" already exists.

Environment

• Sequelize version: v6.28.0
• Node.js version: v14.21.1
• Database & Version: PostgreSQL 14.5
• Connector library & Version: pg@8.8.0

Would you be willing to resolve this issue by submitting a Pull Request?

• Yes, I have the time and I know how to start.
• Yes, I have the time but I will need guidance.
• No, I don't have the time, but my company or I are supporting Sequelize through donations on OpenCollective.
• No, I don't have the time, and I understand that I will need to wait until someone from the community or maintainers is interested in resolving my issue.

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[WikiRik]

I can confirm this on main as well, by copying the following test and adding the enum to there;

sequelize/test/integration/model/sync.test.js

Lines 527 to 555 in 989713a

	it('supports creating tables with cyclic associations', async () => {
	const A = sequelize.define('A', {}, { timestamps: false });
	const B = sequelize.define('B', {}, { timestamps: false });
	// mssql refuses cyclic references unless ON DELETE and ON UPDATE is set to NO ACTION
	const mssqlConstraints = dialect === 'mssql' ? { onDelete: 'NO ACTION', onUpdate: 'NO ACTION' } : null;
	// These models both have a foreign key that references the other model.
	// Sequelize should be able to create them.
	A.belongsTo(B, { foreignKey: { allowNull: false, ...mssqlConstraints } });
	B.belongsTo(A, { foreignKey: { allowNull: false, ...mssqlConstraints } });
	await sequelize.sync();
	const [aFks, bFks] = await Promise.all([
	sequelize.queryInterface.getForeignKeyReferencesForTable(A.getTableName()),
	sequelize.queryInterface.getForeignKeyReferencesForTable(B.getTableName()),
	]);
	expect(aFks.length).to.eq(1);
	expect(aFks[0].referencedTableName).to.eq('Bs');
	expect(aFks[0].referencedColumnName).to.eq('id');
	expect(aFks[0].columnName).to.eq('BId');
	expect(bFks.length).to.eq(1);
	expect(bFks[0].referencedTableName).to.eq('As');
	expect(bFks[0].referencedColumnName).to.eq('id');
	expect(bFks[0].columnName).to.eq('AId');
	});

I think part of the fix should be in changeColumn so I'll tag @ephys in here.

[ephys]

This is a variant of #7649. The cause is the same, but we can add this test to the new suite to make sure