JoinsOn unit test + use all primary keys

callbacks/query.go

@@ -125,7 +125,7 @@ func BuildQuerySQL(db *gorm.DB) {
 						})
 					}
 
-					if join.On != nil {
+					if join.On == nil {
 						exprs := make([]clause.Expression, len(relation.References))
 						for idx, ref := range relation.References {
 							if ref.OwnPrimaryKey {
@@ -153,10 +153,16 @@ func BuildQuerySQL(db *gorm.DB) {
 							ON:    clause.Where{Exprs: exprs},
 						})
 					} else {
+						primaryFields := make([]clause.Column, len(relation.FieldSchema.PrimaryFieldDBNames))
+						for idx, ref := range relation.FieldSchema.PrimaryFieldDBNames {
+							primaryFields[idx] = clause.Column{Table: tableAliasName, Name: ref}
+						}
+
+						exprs := db.Statement.BuildCondition("(?) = (?)", primaryFields, join.On)
 						joins = append(joins, clause.Join{
 							Type:  clause.LeftJoin,
 							Table: clause.Table{Name: relation.FieldSchema.Table, Alias: tableAliasName},
-							ON:    clause.Where{Exprs: []clause.Expression{join.On}},
+							ON:    clause.Where{Exprs: exprs},
 						})
 					}
 				} else {

chainable_api.go

@@ -177,7 +177,7 @@ func (db *DB) Joins(query string, args ...interface{}) (tx *DB) {
 	return
 }
 
-func (db *DB) JoinsOn(query string, on clause.Expression, args ...interface{}) (tx *DB) {
+func (db *DB) JoinsOn(query string, on interface{}, args ...interface{}) (tx *DB) {
 	tx = db.getInstance()
 	tx.Statement.Joins = append(tx.Statement.Joins, join{Name: query, Conds: args, On: on})
 	return

statement.go

@@ -50,7 +50,7 @@ type Statement struct {
 type join struct {
 	Name  string
 	Conds []interface{}
-	On    clause.Expression
+	On    interface{}
 }
 
 // StatementModifier statement modifier interface

tests/joins_test.go

@@ -104,6 +104,26 @@ func TestJoinConds(t *testing.T) {
 	}
 }
 
+func TestJoinOn(t *testing.T) {
+	var user = *GetUser("joins-on", Config{Pets: 2})
+	DB.Save(&user)
+
+	var user1 User
+	onQuery := DB.Select("id").Where("user_id = users.id AND name = ?", "joins-on_pet_1").Model(&Pet{})
+
+	if err := DB.JoinsOn("NamedPet", onQuery).Where("users.name = ?", user.Name).First(&user1).Error; err != nil {
+		t.Fatalf("Failed to load with joins on, got error: %v", err)
+	}
+	AssertEqual(t, user1.NamedPet.Name, "joins-on_pet_1")
+
+	onQuery2 := DB.Select("id").Where("user_id = users.id AND name = ?", "joins-on_pet_2").Model(&Pet{})
+	var user2 User
+	if err := DB.JoinsOn("NamedPet", onQuery2).Where("users.name = ?", user.Name).First(&user2).Error; err != nil {
+		t.Fatalf("Failed to load with joins on, got error: %v", err)
+	}
+	AssertEqual(t, user2.NamedPet.Name, "joins-on_pet_2")
+}
+
 func TestJoinsWithSelect(t *testing.T) {
 	type result struct {
 		ID    uint

utils/tests/models.go

@@ -11,6 +11,7 @@ import (
 // He works in a Company (belongs to), he has a Manager (belongs to - single-table), and also managed a Team (has many - single-table)
 // He speaks many languages (many to many) and has many friends (many to many - single-table)
 // His pet also has one Toy (has one - polymorphic)
+// NamedPet is a reference to a Named `Pets` (has many)
 type User struct {
 	gorm.Model
 	Name      string
@@ -18,6 +19,7 @@ type User struct {
 	Birthday  *time.Time
 	Account   Account
 	Pets      []*Pet
+	NamedPet  *Pet
 	Toys      []Toy `gorm:"polymorphic:Owner"`
 	CompanyID *int
 	Company   Company