Fix sea-orm-cli generating duplicated columns for multi-column foreign keys

[kenkoooo]

sea-orm-cli generate entity generated a malformed Relation for a multi-column foreign key, duplicating columns in the from/to attributes and producing SQL joins whose ON clause matches no rows. This de-duplicates the foreign-key column lists when building the relation, restoring the intended 1:1 column pairing.

PR Info

• Closes sea-orm-cli generates incorrect relation for multi-column foreign key #2662

New Features

• N/A

Bug Fixes

• Multi-column foreign keys that reference a bare unique index generated duplicated columns.

  When a FK targets a bare unique index (CREATE UNIQUE INDEX …) rather than a named UNIQUE / PRIMARY KEY constraint, PostgreSQL's information_schema does not expose the referenced constraint (referential_constraints.unique_constraint_name is empty and the columns are absent from key_column_usage). Schema discovery cannot correlate the local and referenced columns by ordinal position and falls back to their cartesian product — local [f_a, f_b] paired with referenced [a, b, a, b]. From<&TableForeignKey> for Relation stored those lists verbatim, so the generated belongs_to paired two from columns against four to columns:

  // before
  from = "(Column::FA, Column::FB)",
  to   = "(super::first::Column::A, super::first::Column::B, super::first::Column::A, super::first::Column::B)",
  // after
  from = "(Column::FA, Column::FB)",
  to   = "(super::first::Column::A, super::first::Column::B)",

  Fixed by de-duplicating both column lists (preserving first-seen order). A well-formed never repeats a column on either side, so it is a no-op for valid input and only repairs the cartesian-product degeneracy. (The root cause is in sea-schema's discovery query; this is a defensive codegen-side fix that a future sea-schema change could complement.)

Breaking Changes

• None — backward compatible. The de-duplication is a no-op for well-formed foreign keys, so existing correct entities regenerate identically; only the previously-malformed output changes.

Changes

• De-duplicate the local and referenced column lists (order-preserving) in From<&TableForeignKey> for Relation (sea-orm-codegen).
• Regression tests: a unit test for the de-duplication, plus end-to-end transformer tests for the rendered belongs_to (2- and 3-column keys) and the inverse HasOne / HasMany classification.

Verified with cargo test --workspace and cargo test --manifest-path sea-orm-cli/Cargo.toml, and by running sea-orm-cli generate entity against a live PostgreSQL 17 instance with the issue's exact schema.