added arbitrary join conditions as a tag option for many2many relationships

join_table_handler.go

@@ -42,6 +42,7 @@ type JoinTableHandler struct {
 	TableName   string          `sql:"-"`
 	Source      JoinTableSource `sql:"-"`
 	Destination JoinTableSource `sql:"-"`
+	ArbitraryJoinConditions []string `sql:"-"`
 }
 
 // SourceForeignKeys return source foreign keys
@@ -75,6 +76,8 @@ func (s *JoinTableHandler) Setup(relationship *Relationship, tableName string, s
 			AssociationDBName: dbName,
 		})
 	}
+
+	s.ArbitraryJoinConditions = relationship.ArbitraryJoinConditions
 }
 
 // Table return join table's table name
@@ -174,6 +177,7 @@ func (s JoinTableHandler) JoinWith(handler JoinTableHandlerInterface, db *DB, so
 		for _, foreignKey := range s.Destination.ForeignKeys {
 			joinConditions = append(joinConditions, fmt.Sprintf("%v.%v = %v.%v", quotedTableName, scope.Quote(foreignKey.DBName), destinationTableName, scope.Quote(foreignKey.AssociationDBName)))
 		}
+		joinConditions = append(joinConditions, s.ArbitraryJoinConditions...)
 
 		var foreignDBNames []string
 		var foreignFieldNames []string

model_struct.go

@@ -133,6 +133,7 @@ type Relationship struct {
 	AssociationForeignFieldNames []string
 	AssociationForeignDBNames    []string
 	JoinTableHandler             JoinTableHandlerInterface
+	ArbitraryJoinConditions      []string
 }
 
 func getForeignField(column string, fields []*StructField) *StructField {
@@ -339,6 +340,13 @@ func (scope *Scope) GetModelStruct() *ModelStruct {
 										}
 									}
 
+									// Check for arbitrary join conditions supplied in the tag
+
+									if arbitraryConditions,_ := field.TagSettingsGet("ARBITRARY_JOIN_CONDITIONS"); arbitraryConditions != "" {
+										relationship.ArbitraryJoinConditions = strings.Split(arbitraryConditions, ",")
+									}
+
+
 									joinTableHandler := JoinTableHandler{}
 									joinTableHandler.Setup(relationship, ToTableName(many2many), reflectType, elemType)
 									relationship.JoinTableHandler = &joinTableHandler