ouput correct ddl for custom m2m tables (#35)

* ouput correct ddl for custom m2m tables

* fix tests

* fix typo

* cr

README.md

@@ -180,6 +180,39 @@ The provider supports the following databases:
 * SQLite
 * SQL Server
 
+### Frequently Asked Questions
+
+* **Foreign key constraints not generated correctly** -
+  If a [Customize JoinTable](https://gorm.io/docs/many_to_many.html#Customize-JoinTable) is defined in the schema, 
+  you need to use the provider as a [Go Program](#as-go-file) and pass to the `Load` method the tables in their dependency order. i.e.,
+  Join tables after their parent tables.  
+
+  for example if those are your models:
+  ```go
+  type Person struct {
+    ID        int
+    Name      string
+    Addresses []Address `gorm:"many2many:person_addresses;"`
+  }
+
+  type Address struct {
+    ID   int
+    Name string
+  }
+
+  type PersonAddress struct {
+    PersonID  int `gorm:"primaryKey"`
+    AddressID int `gorm:"primaryKey"`
+    CreatedAt time.Time
+    DeletedAt gorm.DeletedAt
+  }
+  ```
+
+  you should use the following code:
+  ```go
+  stmts, err := gormschema.New("mysql").Load(&models.Person{}, &models.Address{}, &models.PersonAddress{})
+  ```
+
 ### License
 
 This project is licensed under the [Apache License 2.0](LICENSE).

gormschema/gorm.go

@@ -5,6 +5,7 @@ import (
 	"database/sql/driver"
 	"errors"
 	"fmt"
+	"slices"
 
 	"ariga.io/atlas-go-sdk/recordriver"
 	"gorm.io/driver/mysql"
@@ -133,12 +134,14 @@ func (d dialector) Migrator(db *gorm.DB) gorm.Migrator {
 }
 
 // HasTable always returns `true`. By returning `true`, gorm.Migrator will try to alter the table to add constraints.
-func (m *migrator) HasTable(dst interface{}) bool {
+func (m *migrator) HasTable(dst any) bool {
 	return true
 }
 
 // CreateConstraints detects constraints on the given model and creates them using `m.dialectMigrator`.
-func (m *migrator) CreateConstraints(models []interface{}) error {
+func (m *migrator) CreateConstraints(models []any) error {
+	// Reverse the order of models to ensure many 2 many tables constraints are created first, assuming they are at the end.
+	slices.Reverse(models)
 	for _, model := range m.ReorderModels(models, true) {
 		err := m.Migrator.RunWithValue(model, func(stmt *gorm.Statement) error {
 			for _, rel := range stmt.Schema.Relationships.Relations {

gormschema/gorm_test.go

@@ -6,6 +6,7 @@ import (
 
 	"ariga.io/atlas-go-sdk/recordriver"
 	ckmodels "ariga.io/atlas-provider-gorm/internal/testdata/circularfks"
+	"ariga.io/atlas-provider-gorm/internal/testdata/customjointable"
 	"ariga.io/atlas-provider-gorm/internal/testdata/models"
 	"github.com/stretchr/testify/require"
 	"gorm.io/gorm"
@@ -58,6 +59,11 @@ func TestMySQLConfig(t *testing.T) {
 	sql, err = l.Load(ckmodels.Location{}, ckmodels.Event{})
 	require.NoError(t, err)
 	requireEqualContent(t, sql, "testdata/mysql_no_fk")
+	resetSession()
+	l = New("mysql")
+	sql, err = l.Load(customjointable.Address{}, customjointable.Person{}, customjointable.PersonAddress{})
+	require.NoError(t, err)
+	requireEqualContent(t, sql, "testdata/mysql_custom_join_table")
 }
 
 func TestSQLServerConfig(t *testing.T) {

gormschema/testdata/mysql_custom_join_table

@@ -0,0 +1,5 @@
+CREATE TABLE `addresses` (`id` bigint AUTO_INCREMENT,`name` longtext,PRIMARY KEY (`id`));
+CREATE TABLE `people` (`id` bigint AUTO_INCREMENT,`name` longtext,PRIMARY KEY (`id`));
+CREATE TABLE `person_addresses` (`person_id` bigint,`address_id` bigint,`created_at` datetime(3) NULL,`deleted_at` datetime(3) NULL,PRIMARY KEY (`person_id`,`address_id`));
+ALTER TABLE `person_addresses` ADD CONSTRAINT `fk_person_addresses_person` FOREIGN KEY (`person_id`) REFERENCES `people`(`id`);
+ALTER TABLE `person_addresses` ADD CONSTRAINT `fk_person_addresses_address` FOREIGN KEY (`address_id`) REFERENCES `addresses`(`id`);

gormschema/testdata/mysql_default

@@ -2,6 +2,6 @@ CREATE TABLE `events` (`eventId` varchar(191),`locationId` varchar(191),PRIMARY
 CREATE TABLE `locations` (`locationId` varchar(191),`eventId` varchar(191),PRIMARY KEY (`locationId`),UNIQUE INDEX `idx_locations_event_id` (`eventId`));
 CREATE TABLE `users` (`id` bigint unsigned AUTO_INCREMENT,`created_at` datetime(3) NULL,`updated_at` datetime(3) NULL,`deleted_at` datetime(3) NULL,`name` longtext,PRIMARY KEY (`id`),INDEX `idx_users_deleted_at` (`deleted_at`));
 CREATE TABLE `pets` (`id` bigint unsigned AUTO_INCREMENT,`created_at` datetime(3) NULL,`updated_at` datetime(3) NULL,`deleted_at` datetime(3) NULL,`name` longtext,`user_id` bigint unsigned,PRIMARY KEY (`id`),INDEX `idx_pets_deleted_at` (`deleted_at`));
-ALTER TABLE `events` ADD CONSTRAINT `fk_locations_event` FOREIGN KEY (`locationId`) REFERENCES `locations`(`locationId`);
-ALTER TABLE `locations` ADD CONSTRAINT `fk_events_location` FOREIGN KEY (`eventId`) REFERENCES `events`(`eventId`);
 ALTER TABLE `pets` ADD CONSTRAINT `fk_users_pets` FOREIGN KEY (`user_id`) REFERENCES `users`(`id`);
+ALTER TABLE `locations` ADD CONSTRAINT `fk_events_location` FOREIGN KEY (`eventId`) REFERENCES `events`(`eventId`);
+ALTER TABLE `events` ADD CONSTRAINT `fk_locations_event` FOREIGN KEY (`locationId`) REFERENCES `locations`(`locationId`);

gormschema/testdata/postgresql_default

@@ -6,6 +6,6 @@ CREATE TABLE "users" ("id" bigserial,"created_at" timestamptz,"updated_at" times
 CREATE INDEX IF NOT EXISTS "idx_users_deleted_at" ON "users" ("deleted_at");
 CREATE TABLE "pets" ("id" bigserial,"created_at" timestamptz,"updated_at" timestamptz,"deleted_at" timestamptz,"name" text,"user_id" bigint,PRIMARY KEY ("id"));
 CREATE INDEX IF NOT EXISTS "idx_pets_deleted_at" ON "pets" ("deleted_at");
-ALTER TABLE "events" ADD CONSTRAINT "fk_locations_event" FOREIGN KEY ("locationId") REFERENCES "locations"("locationId");
-ALTER TABLE "locations" ADD CONSTRAINT "fk_events_location" FOREIGN KEY ("eventId") REFERENCES "events"("eventId");
 ALTER TABLE "pets" ADD CONSTRAINT "fk_users_pets" FOREIGN KEY ("user_id") REFERENCES "users"("id");
+ALTER TABLE "locations" ADD CONSTRAINT "fk_events_location" FOREIGN KEY ("eventId") REFERENCES "events"("eventId");
+ALTER TABLE "events" ADD CONSTRAINT "fk_locations_event" FOREIGN KEY ("locationId") REFERENCES "locations"("locationId");

gormschema/testdata/sqlserver_default

@@ -6,6 +6,6 @@ CREATE TABLE "users" ("id" bigint IDENTITY(1,1),"created_at" datetimeoffset,"upd
 CREATE INDEX "idx_users_deleted_at" ON "users"("deleted_at");
 CREATE TABLE "pets" ("id" bigint IDENTITY(1,1),"created_at" datetimeoffset,"updated_at" datetimeoffset,"deleted_at" datetimeoffset,"name" nvarchar(MAX),"user_id" bigint,PRIMARY KEY ("id"));
 CREATE INDEX "idx_pets_deleted_at" ON "pets"("deleted_at");
-ALTER TABLE "events" ADD CONSTRAINT "fk_locations_event" FOREIGN KEY ("locationId") REFERENCES "locations"("locationId");
-ALTER TABLE "locations" ADD CONSTRAINT "fk_events_location" FOREIGN KEY ("eventId") REFERENCES "events"("eventId");
 ALTER TABLE "pets" ADD CONSTRAINT "fk_users_pets" FOREIGN KEY ("user_id") REFERENCES "users"("id");
+ALTER TABLE "locations" ADD CONSTRAINT "fk_events_location" FOREIGN KEY ("eventId") REFERENCES "events"("eventId");
+ALTER TABLE "events" ADD CONSTRAINT "fk_locations_event" FOREIGN KEY ("locationId") REFERENCES "locations"("locationId");

internal/testdata/customjointable/models.go

@@ -0,0 +1,26 @@
+package customjointable
+
+
+import (
+	"time"
+
+	"gorm.io/gorm"
+)
+
+type Person struct {
+	ID        int
+	Name      string
+	Addresses []Address `gorm:"many2many:person_addresses;"`
+}
+
+type Address struct {
+	ID   int
+	Name string
+}
+
+type PersonAddress struct {
+	PersonID  int `gorm:"primaryKey"`
+	AddressID int `gorm:"primaryKey"`
+	CreatedAt time.Time
+	DeletedAt gorm.DeletedAt
+}