Fluent's deleteForeignKey doesn't generate a valid SQL command

[anthonycastelli]

After spending a bit of time trying to figure out why Fluent's deleteForeignKey(...) wouldn't delete foreign keys, I discovered that the actual SQL command isn't valid.

When using the database's modify command like so

try database.modify(Child.self) { builder in
    builder.deleteForeignKey("user_id, referencing: "id", on: User.self)
}

the SQL query generated returns

ALTER TABLE 'children' DROP 'user_id', DROP '_fluent_fk_children.user_id-users.id'

This isn't valid for deleting key constraints. The correct query should read

ALTER TABLE 'children' DROP 'user_id', DROP FOREIGN KEY '_fluent_fk_children.user_id-users.id'

[tanner0101]

@anthonycastelli which driver are you using? This is likely specific to that SQL flavor and should be fixed there.

[anthonycastelli]

@tanner0101 I'm using MySQL. Should I move this to the MySQL Driver?

[tanner0101]

That would be helpful! Probably needs to be fixed in a similar manner to this: https://github.com/vapor/mysql-driver/blob/master/Sources/MySQLDriver/MySQLSerializer.swift#L47-L65

[tanner0101]

Marking this to ensure there is a test case going forward.