add implicit inverse foreign keys when necessary

generator/processor.go

@@ -158,6 +158,9 @@ func (p *Processor) processPackage() (*Package, error) {
 	}
 
 	pkg.SetModels(models)
+	if err := pkg.addMissingRelationships(); err != nil {
+		return nil, err
+	}
 	for _, ctor := range ctors {
 		p.tryMatchConstructor(pkg, ctor)
 	}

generator/template.go

@@ -80,6 +80,10 @@ func (td *TemplateData) genFieldsTimeTruncations(buf *bytes.Buffer, fields []*Fi
 func (td *TemplateData) GenColumnAddresses(model *Model) string {
 	var buf bytes.Buffer
 	td.genFieldsColumnAddresses(&buf, model.Fields)
+	for _, fk := range model.ImplicitFKs {
+		buf.WriteString(fmt.Sprintf("case \"%s\":\n", fk.Name))
+		buf.WriteString(fmt.Sprintf("return types.Nullable(kallax.VirtualColumn(\"%s\", r, new(%s))), nil\n", fk.Name, fk.Type))
+	}
 	return buf.String()
 }
 
@@ -129,6 +133,10 @@ func (td *TemplateData) IdentifierType(f *Field) string {
 func (td *TemplateData) GenColumnValues(model *Model) string {
 	var buf bytes.Buffer
 	td.genFieldsValues(&buf, model.Fields)
+	for _, fk := range model.ImplicitFKs {
+		buf.WriteString(fmt.Sprintf("case \"%s\":\n", fk.Name))
+		buf.WriteString(fmt.Sprintf("return r.Model.VirtualColumn(col), nil\n"))
+	}
 	return buf.String()
 }
 
@@ -159,6 +167,9 @@ func (td *TemplateData) genFieldsValues(buf *bytes.Buffer, fields []*Field) {
 func (td *TemplateData) GenModelColumns(model *Model) string {
 	var buf bytes.Buffer
 	td.genFieldsColumns(&buf, model.Fields)
+	for _, fk := range model.ImplicitFKs {
+		buf.WriteString(fmt.Sprintf("kallax.NewSchemaField(\"%s\"),\n", fk.Name))
+	}
 	return buf.String()
 }
 

generator/types.go

@@ -153,6 +153,59 @@ func (p *Package) FindModel(name string) *Model {
 	return p.indexedModels[name]
 }
 
+func (p *Package) addMissingRelationships() error {
+	for _, m := range p.Models {
+		for _, f := range m.Fields {
+			if f.Kind == Relationship && !f.IsInverse() {
+				if err := p.trySetFK(f.TypeSchemaName(), f); err != nil {
+					return err
+				}
+			}
+		}
+	}
+
+	return nil
+}
+
+func (p *Package) trySetFK(model string, fk *Field) error {
+	m := p.FindModel(model)
+	if m == nil {
+		return fmt.Errorf("kallax: cannot assign implicit foreign key to non-existent model %s", model)
+	}
+
+	var found bool
+	for _, f := range m.Fields {
+		if f.Kind == Relationship {
+			if f.ForeignKey() == fk.ForeignKey() {
+				found = true
+				break
+			}
+		} else {
+			if f.ColumnName() == fk.ForeignKey() {
+				found = true
+				break
+			}
+		}
+	}
+
+	if !found {
+		for _, ifk := range m.ImplicitFKs {
+			if ifk.Name == fk.ForeignKey() {
+				found = true
+				break
+			}
+		}
+	}
+
+	if !found {
+		m.ImplicitFKs = append(m.ImplicitFKs, ImplicitFK{
+			Name: fk.ForeignKey(),
+			Type: identifierType(fk.Model.ID),
+		})
+	}
+	return nil
+}
+
 const (
 	// StoreNamePattern is the pattern used to name stores.
 	StoreNamePattern = "%sStore"
@@ -182,6 +235,10 @@ type Model struct {
 	Type string
 	// Fields contains the list of fields in the model.
 	Fields []*Field
+	// ImplicitFKs contains the list of fks that are implicit based on
+	// other models' definitions, such as foreign keys with no explicit inverse
+	// on the related model.
+	ImplicitFKs []ImplicitFK
 	// ID contains the identifier field of the model.
 	ID *Field
 	// Events contains the list of events implemented by the model.
@@ -499,6 +556,11 @@ func relationshipsOnFields(fields []*Field) []*Field {
 	return result
 }
 
+type ImplicitFK struct {
+	Name string
+	Type string
+}
+
 // Field is the representation of a model field.
 type Field struct {
 	// Name is the field name.

tests/kallax.go

@@ -611,6 +611,8 @@ func (r *Child) ColumnAddress(col string) (interface{}, error) {
 		return (*kallax.NumericID)(&r.ID), nil
 	case "name":
 		return &r.Name, nil
+	case "parent_id":
+		return types.Nullable(kallax.VirtualColumn("parent_id", r, new(kallax.NumericID))), nil
 
 	default:
 		return nil, fmt.Errorf("kallax: invalid column in Child: %s", col)
@@ -624,6 +626,8 @@ func (r *Child) Value(col string) (interface{}, error) {
 		return r.ID, nil
 	case "name":
 		return r.Name, nil
+	case "parent_id":
+		return r.Model.VirtualColumn(col), nil
 
 	default:
 		return nil, fmt.Errorf("kallax: invalid column in Child: %s", col)
@@ -10773,6 +10777,7 @@ var Schema = &schema{
 			true,
 			kallax.NewSchemaField("id"),
 			kallax.NewSchemaField("name"),
+			kallax.NewSchemaField("parent_id"),
 		),
 		ID:   kallax.NewSchemaField("id"),
 		Name: kallax.NewSchemaField("name"),

tests/store_test.go

@@ -278,10 +278,12 @@ func (s *StoreSuite) TestInsert_RelWithNoInverse() {
 	s.NoError(store.Insert(p))
 	s.NotEqual(0, p.ID)
 
-	var count int
-	err := s.db.QueryRow("SELECT COUNT(*) FROM children WHERE parent_id = $1", p.ID).Scan(&count)
+	p, err := store.FindOne(NewParentQuery().WithChildren(nil))
 	s.NoError(err)
-	s.Equal(3, count)
+	s.Len(p.Children, 3)
+	for _, c := range p.Children {
+		s.NotEqual(int64(0), c.ID)
+	}
 }
 
 func (s *StoreSuite) TestInsert_RelWithNoInverseNoPtr() {
@@ -298,8 +300,10 @@ func (s *StoreSuite) TestInsert_RelWithNoInverseNoPtr() {
 	s.NoError(store.Insert(p))
 	s.NotEqual(0, p.ID)
 
-	var count int
-	err := s.db.QueryRow("SELECT COUNT(*) FROM children WHERE parent_id = $1", p.ID).Scan(&count)
+	p, err := store.FindOne(NewParentNoPtrQuery().WithChildren(nil))
 	s.NoError(err)
-	s.Equal(3, count)
+	s.Len(p.Children, 3)
+	for _, c := range p.Children {
+		s.NotEqual(int64(0), c.ID)
+	}
 }