entc: improve generated comments for edges and fields (#2632)

* replace default field comment with user comment if defined
* use comments defined on edges in generated entities
* add docs for comment method on edges and fields
* update integration to reflect above changes

schema/edge/edge.go

@@ -24,6 +24,7 @@ type Descriptor struct {
 	Required    bool                   // required on creation.
 	StorageKey  *StorageKey            // optional storage-key configuration.
 	Annotations []schema.Annotation    // edge annotations.
+	Comment     string                 // edge comment.
 }
 
 // To defines an association edge between two vertices.
@@ -98,7 +99,8 @@ func (b *assocBuilder) Through(name string, t interface{}) *assocBuilder {
 }
 
 // Comment used to put annotations on the schema.
-func (b *assocBuilder) Comment(string) *assocBuilder {
+func (b *assocBuilder) Comment(c string) *assocBuilder {
+	b.desc.Comment = c
 	return b
 }
 
@@ -165,7 +167,8 @@ func (b *inverseBuilder) StructTag(s string) *inverseBuilder {
 }
 
 // Comment used to put annotations on the schema.
-func (b *inverseBuilder) Comment(string) *inverseBuilder {
+func (b *inverseBuilder) Comment(c string) *inverseBuilder {
+	b.desc.Comment = c
 	return b
 }
 

schema/edge/edge_test.go

@@ -20,8 +20,10 @@ func TestEdge(t *testing.T) {
 	type User struct{ ent.Schema }
 	e := edge.To("friends", User.Type).
 		Required().
+		Comment("comment").
 		Descriptor()
 	assert.False(e.Inverse)
+	assert.Equal("comment", e.Comment)
 	assert.Equal("User", e.Type)
 	assert.Equal("friends", e.Name)
 	assert.True(e.Required)
@@ -39,9 +41,11 @@ func TestEdge(t *testing.T) {
 	e = edge.To("children", Node.Type).
 		From("parent").
 		Unique().
+		Comment("comment").
 		Field("parent_id").
 		Descriptor()
 	assert.Equal("parent_id", e.Field)
+	assert.Equal("comment", e.Comment)
 	assert.Empty(e.Ref.Field)
 
 	t.Log("m2m relation of the same type")