Simple relation enhancement, bi-directional one-to-one relationships

[Former user]

In cases where a bi-directional one-to-one relationship is required a simple enhancement could be made to automatically set uselist=False in some cases. If the referencing column (i.e. the one with the FK object passed in) is unique (either from a unique or primary constraint) then the nature of the relationship is easily deduced.

[Mike Bayer]

im concerned it could lead to confusion due to its implicitness. i.e. "whats this uselist flag and why have i never had to use it before", when a column fails to reflect a unique constraint on a new backend, etc.

[Former user]

an extra paragraph/sentence or two in the relation tutorial and in the reference might be enough?

[Mike Bayer]

well no, because people don't read the documentation. its essentially a surprise behavior. The logic to determine many-to-one/one-to-many is quite involved, but if a foreign key is not detected, it fails loudly. this would be that same logic duplicated (since we need to ensure for multiple-column constraints, ensure that the join condition is simple, etc.) and it wouldn't work in many situations, failing silently. Its too much complexity and inconsistency for not enough benefit.