ent: initial support for edge schemas (#2560)

schema/edge/edge.go

@@ -12,17 +12,18 @@ import (
 
 // A Descriptor for edge configuration.
 type Descriptor struct {
-	Tag         string              // struct tag.
-	Type        string              // edge type.
-	Name        string              // edge name.
-	Field       string              // edge field name (e.g. foreign-key).
-	RefName     string              // ref name; inverse only.
-	Ref         *Descriptor         // edge reference; to/from of the same type.
-	Unique      bool                // unique edge.
-	Inverse     bool                // inverse edge.
-	Required    bool                // required on creation.
-	StorageKey  *StorageKey         // optional storage-key configuration.
-	Annotations []schema.Annotation // edge annotations.
+	Tag         string                 // struct tag.
+	Type        string                 // edge type.
+	Name        string                 // edge name.
+	Field       string                 // edge field name (e.g. foreign-key).
+	RefName     string                 // ref name; inverse only.
+	Ref         *Descriptor            // edge reference; to/from of the same type.
+	Through     *struct{ N, T string } // through type and name.
+	Unique      bool                   // unique edge.
+	Inverse     bool                   // inverse edge.
+	Required    bool                   // required on creation.
+	StorageKey  *StorageKey            // optional storage-key configuration.
+	Annotations []schema.Annotation    // edge annotations.
 }
 
 // To defines an association edge between two vertices.
@@ -86,6 +87,16 @@ func (b *assocBuilder) Field(f string) *assocBuilder {
 	return b
 }
 
+// Through allows setting an "edge schema" to interact explicitly with M2M edges.
+//
+//	edge.To("friends", User.Type).
+//		Through("friendships", Friendship.Type)
+//
+func (b *assocBuilder) Through(name string, t interface{}) *assocBuilder {
+	b.desc.Through = &struct{ N, T string }{N: name, T: typ(t)}
+	return b
+}
+
 // Comment used to put annotations on the schema.
 func (b *assocBuilder) Comment(string) *assocBuilder {
 	return b
@@ -173,6 +184,17 @@ func (b *inverseBuilder) Field(f string) *inverseBuilder {
 	return b
 }
 
+// Through allows setting an "edge schema" to interact explicitly with M2M edges.
+//
+//	edge.From("liked_users", User.Type).
+//		Ref("liked_tweets").
+//		Through("likes", TweetLike.Type)
+//
+func (b *inverseBuilder) Through(name string, t interface{}) *inverseBuilder {
+	b.desc.Through = &struct{ N, T string }{N: name, T: typ(t)}
+	return b
+}
+
 // Annotations adds a list of annotations to the edge object to be used by
 // codegen extensions.
 //

schema/field/annotation.go

@@ -19,6 +19,30 @@ type Annotation struct {
 	//	}
 	//
 	StructTag map[string]string
+
+	// ID defines a multi-field schema identifier. Note,
+	// the annotation is valid only for edge schemas.
+	//
+	//	func (TweetLike) Annotations() []schema.Annotation {
+	//		return []schema.Annotation{
+	//			field.ID("user_id", "tweet_id"),
+	//		}
+	//	}
+	//
+	ID []string
+}
+
+// ID defines a multi-field schema identifier. Note, the
+// annotation is valid only for edge schemas.
+//
+//	func (TweetLike) Annotations() []schema.Annotation {
+//		return []schema.Annotation{
+//			field.ID("user_id", "tweet_id"),
+//		}
+//	}
+//
+func ID(first, second string, fields ...string) *Annotation {
+	return &Annotation{ID: append([]string{first, second}, fields...)}
 }
 
 // Name describes the annotation name.
@@ -45,10 +69,13 @@ func (a Annotation) Merge(other schema.Annotation) schema.Annotation {
 		}
 		a.StructTag[k] = v
 	}
+	if len(ant.ID) > 0 {
+		a.ID = ant.ID
+	}
 	return a
 }
 
-var (
-	_ schema.Annotation = (*Annotation)(nil)
-	_ schema.Merger     = (*Annotation)(nil)
-)
+var _ interface {
+	schema.Annotation
+	schema.Merger
+} = (*Annotation)(nil)