fix comments lost in generated DDL.

[chaosue]

no comments generated on DDL in database, this problem should be fixed, or there's no way to get descriptions for the tables and their columns unless checking the schema golang code, which may lead to impossibility of reverse engineerings and incomprehension for DBA.

[a8m]

Thanks for adding this, @chaosue. It's appreciated! 🙏

I think this change should be added to EntSQL annotation, because I prefer not to trigger migration changes to all users that use the Comment option today. Also, some users, like myself, care only about the code comments and do not need database comments.

[a8m]

Hey @chaosue! Any update on this PR?

[a8m]

After a discussion with Cheng on Discord, we think the configuration can be simplified by providing a single annotation in the entsql package to indicate that columns' comments should also be stored on the database schema. For example:

func (T) Annotations() []schema.Annotation {
    return []schema.Annotation{
        // WithComments indicates that all entity comments
        // should be stored in the database schema as well.
        entsql.WithComments(true),
    }
}

Table comments can be implemented once #3164 is merged, and an entsql.Comment(string) annotation can be added in case there are requests for mixed comments (one for code generation, and one for the database).

[huiwanggo]

table comment ? entsql.WithComments(true), schema.Comment(string) SQL DDL not work。Will this feature be supported? @a8m

[suncle1993]

table comment ? entsql.WithComments(true), schema.Comment(string) SQL DDL not work。Will this feature be supported? @a8m

if you want to generate table comment and column comment, you can upgrade your entgo to master version. And then use like this:

type T struct {
	ent.Schema
}

func (T) Annotations() []schema.Annotation {
	return []schema.Annotation{
		entsql.Annotation{Table: "t"},
		entsql.WithComments(true),
		schema.Comment("t is like business unit table"),
	}
}

func (T) Fields() []ent.Field {
	return []ent.Field{
		field.String("name").Comment("unique name"),
		field.String("description").Default("").Comment("xxx"),
	}
}