Validates Ecto.Changeset.foreign_key_constraint/3 annotations for Postgres FKs.

Examples

With a foreign key on orders.account_id, before:

def changeset(order, attrs) do
  order
  |> Ecto.Changeset.cast(attrs, [:account_id])
  |> Ecto.Changeset.validate_required([:account_id])
end

The database rejects missing accounts, but the caller may see a low-level constraint error instead of an :account_id changeset error.

After, annotate the changeset with the matching constraint:

def changeset(order, attrs) do
  order
  |> Ecto.Changeset.cast(attrs, [:account_id])
  |> Ecto.Changeset.validate_required([:account_id])
  |> Ecto.Changeset.foreign_key_constraint(:account_id)
end

Ecto can report the invalid relationship through the changeset API.

Notes

The check skips dynamic cast or change field lists and foreign keys whose columns cannot be mapped to Ecto schema fields.

Options

The check discovers compiled Ecto schemas through reflection, parses source files for conservative changeset candidates, and only requires foreign_key_constraint/3 when a candidate casts the local foreign-key field. Dynamic cast/change field lists are skipped for v1.

Pass paths: [...] so Bylaw can parse source AST for user-defined changeset functions:

{Bylaw.Db.Adapters.Postgres.Checks.EctoChangesetForeignKeyConstraints,
 paths: ["lib/my_app"]}

When the repo can report config()[:otp_app], schema module discovery is derived from it. Use schema_modules: [...] when the check should inspect an explicit set of schemas instead:

{Bylaw.Db.Adapters.Postgres.Checks.EctoChangesetForeignKeyConstraints,
 paths: ["lib/my_app/billing"],
 schema_modules: [MyApp.Billing.Invoice, MyApp.Billing.Payment]}

Use rules: [...] to scope the Postgres constraints considered by the check:

{Bylaw.Db.Adapters.Postgres.Checks.EctoChangesetForeignKeyConstraints,
 paths: ["lib/my_app"],
 rules: [
   [
     only: [schema: "public"],
     except: [[table: "events", column: "actor_id"]]
   ]
 ]}

Usage

Add this module to the checks passed to Bylaw.Db.Adapters.Postgres.validate/2. See the README usage section for the full ExUnit setup.