Gorm many2many with Non-PrimaryKey(unique index) throw ERROR: primaryKey column of relation does not exist

GORM Playground Link

https://github.com/go-gorm/playground/pull/630

Description

I find that many2many does not support Non-PrimaryKey.

Reproduce steps:

GORM_DIALECT=postgres go test -v

CREATE TABLE "stu_compannys" ("companny_name" text,"stuname" text,PRIMARY KEY ("companny_name","stuname"),CONSTRAINT "fk_stu_compannys_companny" FOREIGN KEY ("companny_name") REFERENCES "compannies"("name"),CONSTRAINT "fk_stu_compannys_stu" FOREIGN KEY ("stuname") REFERENCES "stus"("stuname"))

main_test.go:28 ERROR: column "stu_id" of relation "stu_compannys" does not exist (SQLSTATE 42703)

Comment From: twocs

The description of the problem doesn't match the code. The problem in the code is that the Companny table has a many2many relationship with the Stu table, and then Stu table has a separate many2many relationship with the Companny table.

However, the many2many relationship was only defined halfway, on the Companny slice Stus []Stu. But on the Stu slice []Companny there was only gorm:"many2many" without details of how Gorm should go about joining the Stu's Compannies slice with the other table.

Just update the code to:

type Companny struct {
    ID   int    `gorm:"primarykey"`
    Name string `gorm:"index:,unique"`
    Stus []Stu `gorm:"many2many:stu_compannys;foreignKey:Name;joinForeignKey:CompannyName;References:Stuname;joinReferences:Stuname;"`
}
type Stu struct {
    ID        int       `gorm:"primarykey"`
    Stuname   string    `gorm:"index:,unique"`
    Compannies []Companny `gorm:"many2many:stu_compannys;foreignKey:Stuname;joinForeignKey:Stuname;References:Name;joinReferences:CompannyName;"`
}

Also the assertion should be updated to access the Error, and then it passes:

if err.Error!=nil{
  t.Fatal(err.Error)
}