feat: Null enums types (#1485)

* Generate Null Enum type 

- We need to import driver to comply with the Valuer interface.
- The Scan method uses the Scan from the Non Null Enum type

* Map Custom Null enum type with database typing function

* regen examples and internal endtoend tests 

- Regen with the Null types

* Add Enum examples with nullable fields

* Add NullableEnum output to e2e test

* Update generated files with correct version


.

Co-authored-by: Stephane <sbres@coinshares.com>
Co-authored-by: Avi Zimmerman <avi.zimmerman@gmail.com>

Author: 3 people

examples/batch/postgresql/models.go

@@ -264,6 +264,7 @@ func (i *importer) modelImports() fileImports {
 
 	if len(i.Enums) > 0 {
 		std["fmt"] = struct{}{}
+		std["database/sql/driver"] = struct{}{}
 	}
 
 	return sortedImports(std, pkg)

examples/booktest/mysql/models.go

@@ -86,10 +86,17 @@ func mysqlType(req *plugin.CodeGenRequest, col *plugin.Column) string {
 		for _, schema := range req.Catalog.Schemas {
 			for _, enum := range schema.Enums {
 				if enum.Name == columnType {
-					if schema.Name == req.Catalog.DefaultSchema {
-						return StructName(enum.Name, req.Settings)
+					if notNull {
+						if schema.Name == req.Catalog.DefaultSchema {
+							return StructName(enum.Name, req.Settings)
+						}
+						return StructName(schema.Name+"_"+enum.Name, req.Settings)
+					} else {
+						if schema.Name == req.Catalog.DefaultSchema {
+							return "Null" + StructName(enum.Name, req.Settings)
+						}
+						return "Null" + StructName(schema.Name+"_"+enum.Name, req.Settings)
 					}
-					return StructName(schema.Name+"_"+enum.Name, req.Settings)
 				}
 			}
 		}

examples/booktest/postgresql/models.go

@@ -280,10 +280,17 @@ func postgresType(req *plugin.CodeGenRequest, col *plugin.Column) string {
 
 			for _, enum := range schema.Enums {
 				if rel.Name == enum.Name && rel.Schema == schema.Name {
-					if schema.Name == req.Catalog.DefaultSchema {
-						return StructName(enum.Name, req.Settings)
+					if notNull {
+						if schema.Name == req.Catalog.DefaultSchema {
+							return StructName(enum.Name, req.Settings)
+						}
+						return StructName(schema.Name+"_"+enum.Name, req.Settings)
+					} else {
+						if schema.Name == req.Catalog.DefaultSchema {
+							return "Null" + StructName(enum.Name, req.Settings)
+						}
+						return "Null" + StructName(schema.Name+"_"+enum.Name, req.Settings)
 					}
-					return StructName(schema.Name+"_"+enum.Name, req.Settings)
 				}
 			}
 

examples/ondeck/mysql/models.go

@@ -87,6 +87,30 @@ func (e *{{.Name}}) Scan(src interface{}) error {
 	return nil
 }
 
+type Null{{.Name}} struct {
+	{{.Name}} {{.Name}}
+	Valid  bool // Valid is true if String is not NULL
+}
+
+// Scan implements the Scanner interface.
+func (ns *Null{{.Name}}) Scan(value interface{}) error {
+	if value == nil {
+		ns.{{.Name}}, ns.Valid = "", false
+		return nil
+	}
+	ns.Valid = true
+	return ns.{{.Name}}.Scan(value)
+}
+
+// Value implements the driver Valuer interface.
+func (ns Null{{.Name}}) Value() (driver.Value, error) {
+	if !ns.Valid {
+		return nil, nil
+	}
+	return ns.{{.Name}}, nil
+}
+
+
 {{ if $.EmitEnumValidMethod }}
 func (e {{.Name}}) Valid() bool {
   switch e {