New collection being created when choosing an existing one for a junction

[kashike]

Describe the Bug

Creating a many-to-many relationship field that utilizes an existing junction collection works successfully, however Directus still creates a new collection/table which is then not used.

I've traced this down to the following area:

• directus/app/src/modules/settings/routes/data-model/field-detail/store/alterations/m2m.ts

  Line 135 in 79c2701

  const automaticJunctionCollectionName = getAutomaticJunctionCollectionName(currentCollection, relatedCollection);

• directus/app/src/modules/settings/routes/data-model/utils/get-junction-collection-name.ts

  Lines 3 to 23 in 79c2701

  	export function getAutomaticJunctionCollectionName(collectionA: string, field: string) {
  	let index = 0;
  	let name = getName(index);
  	while (collectionExists(name)) {
  	index++;
  	name = getName(index);
  	}
  	return name;
  	function getName(index: number) {
  	let name = `${collectionA}_${field}`;
  	if (name.startsWith('directus_')) {
  	name = 'junction_' + name;
  	}
  	if (index) return name + '_' + index;
  	return name;
  	}

• directus/app/src/modules/settings/routes/data-model/field-detail/store/alterations/m2m.ts

  Lines 165 to 190 in 79c2701

  	if (!junctionCollection || collectionExists(junctionCollection)) {
  	set(updates, 'collections.junction', undefined);
  	} else {
  	set(updates, 'collections.junction', {
  	collection: junctionCollection,
  	meta: {
  	hidden: true,
  	icon: 'import_export',
  	},
  	schema: {
  	name: junctionCollection,
  	},
  	fields: [
  	{
  	field: 'id',
  	type: 'integer',
  	schema: {
  	has_auto_increment: true,
  	},
  	meta: {
  	hidden: true,
  	},
  	},
  	],
  	});
  	}

The if (!junctionCollection || collectionExists(junctionCollection)) check specifically is where the logic fails, as the collection name being checked is not the one that is actually being used for the junction.

To Reproduce

1. Insert the following data:

create table issue_abc
(
  id   uuid not null primary key default gen_random_uuid(),
  name text not null
);

create table issue_def
(
  id   uuid not null primary key default gen_random_uuid(),
  name text not null
);

create table issue_abc_issue_def
(
  id           serial primary key,
  issue_abc_id uuid not null references issue_abc (id) on delete cascade,
  issue_def_id uuid not null references issue_def (id) on delete cascade
);

insert into issue_abc (name) values ('ABC');
insert into issue_def (name) values ('DEF');

2. Import the Issue Abc and Issue Def collections in the Directus UI.
3. In the Issue Abc collection, create a new field using the advanced creation modal of type Many to Many Relationship as follows :

• Schema
  • Key: thing
• Relationship
  • Related Collection: issue_def
  • Junction Collection: issue_abc_issue_def (remove the _1 by default at the end)
  • Relational Triggers: all set to Delete the issue_abc_issue_def item (cascade)

4. Check your database, and you'll see that a new issue_abc_issue_def_1 table has been created.
5. Go to the content editor, Issue Abc collection, and edit the item to add a value to the Thing field.
6. Check your database, and you'll see that the relationship has been created in the issue_abc_issue_def table, as is expected.

Directus Version

v10.9.3

Hosting Strategy

Self-Hosted (Docker Image)

[luigigorlero]

This also seems to affect M2A