improve generics version Joins support

callbacks/query.go

@@ -146,10 +146,14 @@ func BuildQuerySQL(db *gorm.DB) {
 
 					if isRelations {
 						genJoinClause := func(joinType clause.JoinType, parentTableName string, relation *schema.Relationship) clause.Join {
-							tableAliasName := relation.Name
+							tableAliasName := join.Alias
+
+							if tableAliasName == "" {
+								tableAliasName = relation.Name
 								if parentTableName != clause.CurrentTable {
 									tableAliasName = utils.NestedRelationName(parentTableName, tableAliasName)
 								}
+							}
 
 							columnStmt := gorm.Statement{
 								Table: tableAliasName, DB: db, Schema: relation.FieldSchema,
@@ -167,6 +171,13 @@ func BuildQuerySQL(db *gorm.DB) {
 								}
 							}
 
+							if join.Expression != nil {
+								return clause.Join{
+									Type:       join.JoinType,
+									Expression: join.Expression,
+								}
+							}
+
 							exprs := make([]clause.Expression, len(relation.References))
 							for idx, ref := range relation.References {
 								if ref.OwnPrimaryKey {

clause/joins.go

@@ -19,15 +19,15 @@ type JoinTarget struct {
 }
 
 func Has(name string) JoinTarget {
-	return JoinTarget{Type: LeftJoin, Association: name}
+	return JoinTarget{Type: InnerJoin, Association: name}
 }
 
 func (jt JoinType) Association(name string) JoinTarget {
 	return JoinTarget{Type: jt, Association: name}
 }
 
-func (jt JoinType) Subquery(subquery Expression) JoinTarget {
+func (jt JoinType) AssociationFrom(name string, subquery Expression) JoinTarget {
-	return JoinTarget{Type: jt, Subquery: subquery}
+	return JoinTarget{Type: jt, Association: name, Subquery: subquery}
 }
 
 func (jt JoinTarget) As(name string) JoinTarget {

generics.go

@@ -3,8 +3,11 @@ package gorm
 import (
 	"context"
 	"database/sql"
+	"fmt"
+	"strings"
 
 	"gorm.io/gorm/clause"
+	"gorm.io/gorm/logger"
 )
 
 type Interface[T any] interface {
@@ -28,7 +31,7 @@ type ChainInterface[T any] interface {
 	Or(query interface{}, args ...interface{}) ChainInterface[T]
 	Limit(offset int) ChainInterface[T]
 	Offset(offset int) ChainInterface[T]
-	Joins(query clause.JoinTarget, args func(db ChainInterface[any], joinTable clause.Table, curTable clause.Table) ChainInterface[any]) ChainInterface[T]
+	Joins(query clause.JoinTarget, args func(db QueryInterface, joinTable clause.Table, curTable clause.Table) QueryInterface) ChainInterface[T]
 	Select(query string, args ...interface{}) ChainInterface[T]
 	Omit(columns ...string) ChainInterface[T]
 	MapColumns(m map[string]string) ChainInterface[T]
@@ -38,6 +41,8 @@ type ChainInterface[T any] interface {
 	Order(value interface{}) ChainInterface[T]
 	Preload(query string, args ...interface{}) ChainInterface[T]
 
+	Build(builder clause.Builder)
+
 	Delete(ctx context.Context) (rowsAffected int, err error)
 	Update(ctx context.Context, name string, value any) (rowsAffected int, err error)
 	Updates(ctx context.Context, t T) (rowsAffected int, err error)
@@ -55,6 +60,14 @@ type ExecInterface[T any] interface {
 	Rows(ctx context.Context) (*sql.Rows, error)
 }
 
+type QueryInterface interface {
+	Select(...string) QueryInterface
+	Omit(...string) QueryInterface
+	Where(query interface{}, args ...interface{}) QueryInterface
+	Not(query interface{}, args ...interface{}) QueryInterface
+	Or(query interface{}, args ...interface{}) QueryInterface
+}
+
 type op func(*DB) *DB
 
 func G[T any](db *DB, opts ...clause.Expression) Interface[T] {
@@ -185,9 +198,77 @@ func (c chainG[T]) Offset(offset int) ChainInterface[T] {
 	})
 }
 
-func (c chainG[T]) Joins(query clause.JoinTarget, args func(db ChainInterface[any], joinTable clause.Table, curTable clause.Table) ChainInterface[any]) ChainInterface[T] {
+type query struct {
-	// TODO
+	db *DB
-	return nil
+}
+
+func (q query) Where(query interface{}, args ...interface{}) QueryInterface {
+	q.db.Where(query, args...)
+	return q
+}
+
+func (q query) Or(query interface{}, args ...interface{}) QueryInterface {
+	q.db.Where(query, args...)
+	return q
+}
+
+func (q query) Not(query interface{}, args ...interface{}) QueryInterface {
+	q.db.Where(query, args...)
+	return q
+}
+
+func (q query) Select(columns ...string) QueryInterface {
+	q.db.Select(columns)
+	return q
+}
+
+func (q query) Omit(columns ...string) QueryInterface {
+	q.db.Omit(columns...)
+	return q
+}
+
+func (c chainG[T]) Joins(jt clause.JoinTarget, args func(db QueryInterface, joinTable clause.Table, curTable clause.Table) QueryInterface) ChainInterface[T] {
+	return c.with(func(db *DB) *DB {
+		if jt.Table == "" {
+			jt.Table = clause.JoinTable(strings.Split(jt.Association, ".")...).Name
+		}
+
+		q := query{db: db.Session(&Session{NewDB: true}).getInstance().Table(jt.Table)}
+		if args != nil {
+			args(q, clause.Table{Name: jt.Table}, clause.Table{Name: clause.CurrentTable})
+		}
+
+		j := join{
+			Name:     jt.Association,
+			Alias:    jt.Table,
+			Selects:  q.db.Statement.Selects,
+			Omits:    q.db.Statement.Omits,
+			JoinType: jt.Type,
+		}
+
+		if where, ok := q.db.Statement.Clauses["WHERE"].Expression.(clause.Where); ok {
+			j.On = &where
+		}
+
+		if jt.Subquery != nil {
+			joinType := j.JoinType
+			if joinType == "" {
+				joinType = clause.LeftJoin
+			}
+
+			expr := clause.NamedExpr{SQL: fmt.Sprintf("%s JOIN (?) AS ?", joinType), Vars: []interface{}{jt.Subquery, clause.Table{Name: j.Alias}}}
+
+			if j.On != nil {
+				expr.SQL += " ON ?"
+				expr.Vars = append(expr.Vars, clause.AndConditions{Exprs: j.On.Exprs})
+			}
+
+			j.Expression = expr
+		}
+
+		db.Statement.Joins = append(db.Statement.Joins, j)
+		return db
+	})
 }
 
 func (c chainG[T]) Select(query string, args ...interface{}) ChainInterface[T] {
@@ -261,6 +342,43 @@ func (c chainG[T]) Count(ctx context.Context, column string) (result int64, err
 	return
 }
 
+func (c chainG[T]) Build(builder clause.Builder) {
+	subdb := c.getInstance()
+	subdb.Logger = logger.Discard
+	subdb.DryRun = true
+
+	if stmt, ok := builder.(*Statement); ok {
+		if subdb.Statement.SQL.Len() > 0 {
+			var (
+				vars = subdb.Statement.Vars
+				sql  = subdb.Statement.SQL.String()
+			)
+
+			subdb.Statement.Vars = make([]interface{}, 0, len(vars))
+			for _, vv := range vars {
+				subdb.Statement.Vars = append(subdb.Statement.Vars, vv)
+				bindvar := strings.Builder{}
+				subdb.BindVarTo(&bindvar, subdb.Statement, vv)
+				sql = strings.Replace(sql, bindvar.String(), "?", 1)
+			}
+
+			subdb.Statement.SQL.Reset()
+			subdb.Statement.Vars = stmt.Vars
+			if strings.Contains(sql, "@") {
+				clause.NamedExpr{SQL: sql, Vars: vars}.Build(subdb.Statement)
+			} else {
+				clause.Expr{SQL: sql, Vars: vars}.Build(subdb.Statement)
+			}
+		} else {
+			subdb.Statement.Vars = append(stmt.Vars, subdb.Statement.Vars...)
+			subdb.callbacks.Query().Execute(subdb)
+		}
+
+		builder.WriteString(subdb.Statement.SQL.String())
+		stmt.Vars = subdb.Statement.Vars
+	}
+}
+
 type execG[T any] struct {
 	g *g[T]
 }

scan.go

@@ -4,6 +4,7 @@ import (
 	"database/sql"
 	"database/sql/driver"
 	"reflect"
+	"strings"
 	"time"
 
 	"gorm.io/gorm/schema"
@@ -244,6 +245,12 @@ func Scan(rows Rows, db *DB, mode ScanMode) {
 							matchedFieldCount[column] = 1
 						}
 					} else if names := utils.SplitNestedRelationName(column); len(names) > 1 { // has nested relation
+						for _, join := range db.Statement.Joins {
+							if join.Alias == names[0] {
+								names = append(strings.Split(join.Name, "."), names[len(names)-1])
+							}
+						}
+
 						if rel, ok := sch.Relationships.Relations[names[0]]; ok {
 							subNameCount := len(names)
 							// nested relation fields

statement.go

@@ -51,10 +51,12 @@ type Statement struct {
 
 type join struct {
 	Name       string
+	Alias      string
 	Conds      []interface{}
 	On         *clause.Where
 	Selects    []string
 	Omits      []string
+	Expression clause.Expression
 	JoinType   clause.JoinType
 }
 
@@ -322,6 +324,11 @@ func (stmt *Statement) BuildCondition(query interface{}, args ...interface{}) []
 			arg, _ = valuer.Value()
 		}
 
+		curTable := stmt.Table
+		if curTable == "" {
+			curTable = clause.CurrentTable
+		}
+
 		switch v := arg.(type) {
 		case clause.Expression:
 			conds = append(conds, v)
@@ -352,7 +359,8 @@ func (stmt *Statement) BuildCondition(query interface{}, args ...interface{}) []
 			sort.Strings(keys)
 
 			for _, key := range keys {
-				conds = append(conds, clause.Eq{Column: key, Value: v[key]})
+				column := clause.Column{Name: key, Table: curTable}
+				conds = append(conds, clause.Eq{Column: column, Value: v[key]})
 			}
 		case map[string]interface{}:
 			keys := make([]string, 0, len(v))
@@ -363,12 +371,13 @@ func (stmt *Statement) BuildCondition(query interface{}, args ...interface{}) []
 
 			for _, key := range keys {
 				reflectValue := reflect.Indirect(reflect.ValueOf(v[key]))
+				column := clause.Column{Name: key, Table: curTable}
 				switch reflectValue.Kind() {
 				case reflect.Slice, reflect.Array:
 					if _, ok := v[key].(driver.Valuer); ok {
-						conds = append(conds, clause.Eq{Column: key, Value: v[key]})
+						conds = append(conds, clause.Eq{Column: column, Value: v[key]})
 					} else if _, ok := v[key].(Valuer); ok {
-						conds = append(conds, clause.Eq{Column: key, Value: v[key]})
+						conds = append(conds, clause.Eq{Column: column, Value: v[key]})
 					} else {
 						// optimize reflect value length
 						valueLen := reflectValue.Len()
@@ -377,10 +386,10 @@ func (stmt *Statement) BuildCondition(query interface{}, args ...interface{}) []
 							values[i] = reflectValue.Index(i).Interface()
 						}
 
-						conds = append(conds, clause.IN{Column: key, Values: values})
+						conds = append(conds, clause.IN{Column: column, Values: values})
 					}
 				default:
-					conds = append(conds, clause.Eq{Column: key, Value: v[key]})
+					conds = append(conds, clause.Eq{Column: column, Value: v[key]})
 				}
 			}
 		default:
@@ -407,9 +416,9 @@ func (stmt *Statement) BuildCondition(query interface{}, args ...interface{}) []
 						if selected || (!restricted && field.Readable) {
 							if v, isZero := field.ValueOf(stmt.Context, reflectValue); !isZero || selected {
 								if field.DBName != "" {
-									conds = append(conds, clause.Eq{Column: clause.Column{Table: clause.CurrentTable, Name: field.DBName}, Value: v})
+									conds = append(conds, clause.Eq{Column: clause.Column{Table: curTable, Name: field.DBName}, Value: v})
 								} else if field.DataType != "" {
-									conds = append(conds, clause.Eq{Column: clause.Column{Table: clause.CurrentTable, Name: field.Name}, Value: v})
+									conds = append(conds, clause.Eq{Column: clause.Column{Table: curTable, Name: field.Name}, Value: v})
 								}
 							}
 						}
@@ -421,9 +430,9 @@ func (stmt *Statement) BuildCondition(query interface{}, args ...interface{}) []
 							if selected || (!restricted && field.Readable) {
 								if v, isZero := field.ValueOf(stmt.Context, reflectValue.Index(i)); !isZero || selected {
 									if field.DBName != "" {
-										conds = append(conds, clause.Eq{Column: clause.Column{Table: clause.CurrentTable, Name: field.DBName}, Value: v})
+										conds = append(conds, clause.Eq{Column: clause.Column{Table: curTable, Name: field.DBName}, Value: v})
 									} else if field.DataType != "" {
-										conds = append(conds, clause.Eq{Column: clause.Column{Table: clause.CurrentTable, Name: field.Name}, Value: v})
+										conds = append(conds, clause.Eq{Column: clause.Column{Table: curTable, Name: field.Name}, Value: v})
 									}
 								}
 							}
@@ -448,14 +457,14 @@ func (stmt *Statement) BuildCondition(query interface{}, args ...interface{}) []
 						}
 
 						if len(values) > 0 {
-							conds = append(conds, clause.IN{Column: clause.PrimaryColumn, Values: values})
+							conds = append(conds, clause.IN{Column: clause.Column{Table: curTable, Name: clause.PrimaryKey}, Values: values})
 							return []clause.Expression{clause.And(conds...)}
 						}
 						return nil
 					}
 				}
 
-				conds = append(conds, clause.IN{Column: clause.PrimaryColumn, Values: args})
+				conds = append(conds, clause.IN{Column: clause.Column{Table: curTable, Name: clause.PrimaryKey}, Values: args})
 			}
 		}
 	}

tests/generics_test.go

@@ -44,7 +44,7 @@ func TestGenericsCreate(t *testing.T) {
 
 	if u, err := gorm.G[User](DB).Omit("name").Where("name = ?", user.Name).First(ctx); err != nil {
 		t.Fatalf("failed to find user, got error: %v", err)
-	} else if u.Name != "" || u.Age != u.Age {
+	} else if u.Name != "" || u.Age != user.Age {
 		t.Errorf("found invalid user, got %v, expect %v", u, user)
 	}
 
@@ -92,7 +92,6 @@ func TestGenericsCreateInBatches(t *testing.T) {
 
 	found, err := gorm.G[User](DB).Raw("SELECT * FROM users WHERE name LIKE ?", "GenericsCreateInBatches%").Find(ctx)
 	if len(found) != len(batch) {
-		fmt.Println(found)
 		t.Errorf("expected %d from Raw Find, got %d", len(batch), len(found))
 	}
 
@@ -282,10 +281,12 @@ func TestGenericsJoinsAndPreload(t *testing.T) {
 	db := gorm.G[User](DB)
 
 	u := User{Name: "GenericsJoins", Company: Company{Name: "GenericsCompany"}}
-	db.Create(ctx, &u)
+	u2 := User{Name: "GenericsJoins_2", Company: Company{Name: "GenericsCompany_2"}}
+	u3 := User{Name: "GenericsJoins_3", Company: Company{Name: "GenericsCompany_3"}}
+	db.CreateInBatches(ctx, &[]User{u3, u, u2}, 10)
 
-	// LEFT JOIN + WHERE
+	// Inner JOIN + WHERE
-	result, err := db.Joins(clause.Has("Company"), func(db gorm.ChainInterface[any], joinTable clause.Table, curTable clause.Table) gorm.ChainInterface[any] {
+	result, err := db.Joins(clause.Has("Company"), func(db gorm.QueryInterface, joinTable clause.Table, curTable clause.Table) gorm.QueryInterface {
 		return db.Where("?.name = ?", joinTable, u.Company.Name)
 	}).First(ctx)
 	if err != nil {
@@ -295,9 +296,9 @@ func TestGenericsJoinsAndPreload(t *testing.T) {
 		t.Fatalf("Joins expected %s, got %+v", u.Name, result)
 	}
 
-	// JOIN
+	// Inner JOIN + WHERE with map
-	result, err = db.Joins(clause.Has("Company"), func(db gorm.ChainInterface[any], joinTable clause.Table, curTable clause.Table) gorm.ChainInterface[any] {
+	result, err = db.Joins(clause.Has("Company"), func(db gorm.QueryInterface, joinTable clause.Table, curTable clause.Table) gorm.QueryInterface {
-		return nil
+		return db.Where(map[string]any{"name": u.Company.Name})
 	}).First(ctx)
 	if err != nil {
 		t.Fatalf("Joins failed: %v", err)
@@ -306,10 +307,8 @@ func TestGenericsJoinsAndPreload(t *testing.T) {
 		t.Fatalf("Joins expected %s, got %+v", u.Name, result)
 	}
 
-	// Left JOIN
+	// Left JOIN w/o WHERE
-	result, err = db.Joins(clause.LeftJoin.Association("Company").As("t"), func(db gorm.ChainInterface[any], joinTable clause.Table, curTable clause.Table) gorm.ChainInterface[any] {
+	result, err = db.Joins(clause.LeftJoin.Association("Company"), nil).Where(map[string]any{"name": u.Name}).First(ctx)
-		return nil
-	}).First(ctx)
 	if err != nil {
 		t.Fatalf("Joins failed: %v", err)
 	}
@@ -317,6 +316,36 @@ func TestGenericsJoinsAndPreload(t *testing.T) {
 		t.Fatalf("Joins expected %s, got %+v", u.Name, result)
 	}
 
+	// Left JOIN + Alias WHERE
+	result, err = db.Joins(clause.LeftJoin.Association("Company").As("t"), func(db gorm.QueryInterface, joinTable clause.Table, curTable clause.Table) gorm.QueryInterface {
+		if joinTable.Name != "t" {
+			t.Fatalf("Join table should be t, but got %v", joinTable.Name)
+		}
+		return db.Where("?.name = ?", joinTable, u.Company.Name)
+	}).Where(map[string]any{"name": u.Name}).First(ctx)
+	if err != nil {
+		t.Fatalf("Joins failed: %v", err)
+	}
+	if result.Name != u.Name || result.Company.Name != u.Company.Name {
+		t.Fatalf("Joins expected %s, got %+v", u.Name, result)
+	}
+
+	// Raw Subquery JOIN + WHERE
+	result, err = db.Joins(clause.LeftJoin.AssociationFrom("Company", gorm.G[Company](DB)).As("t"),
+		func(db gorm.QueryInterface, joinTable clause.Table, curTable clause.Table) gorm.QueryInterface {
+			if joinTable.Name != "t" {
+				t.Fatalf("Join table should be t, but got %v", joinTable.Name)
+			}
+			return db.Where("?.name = ?", joinTable, u.Company.Name)
+		},
+	).Where(map[string]any{"name": u2.Name}).First(ctx)
+	if err != nil {
+		t.Fatalf("Raw subquery join failed: %v", err)
+	}
+	if result.Name != u2.Name || result.Company.Name != u.Company.Name {
+		t.Fatalf("Joins expected %s, got %+v", u.Name, result)
+	}
+
 	// Preload
 	result3, err := db.Preload("Company").Where("name = ?", u.Name).First(ctx)
 	if err != nil {