Allow adding additional tags via goField directive

[asif-mahmud]

It is not a bug report, more like a feature request. Currently, if we add additional tags in the generated model structures, and then re-generate after adding more types in the schema, the manually added tags get overwritten. So it requires to add those tags again after each generate. This could be made automatic by allowing the goField directive to have additional tag string or strings to include in the generated models. If i was not clear please let me know. Also if there is already some approach to take care of additional tags in the models, i ll be glad to check that out.

[tprebs]

Though this is not adding tags to goField, #1650 would resolve this issue as you could create a custom directive which adds the tags each time during generation.

e.g.

directive @goTags(tags: [String]!) on INPUT_FIELD_DEFINITION
    | FIELD_DEFINITION

and custom hook

func tagFieldHook(td *ast.Definition, fd *ast.FieldDefinition, f *modelgen.Field) (*modelgen.Field, error) {

	c := fd.Directives.ForName("goTags")
	if c != nil {
		if ma := c.Arguments.ForName("tags"); ma != nil {
			if tags, err := ma.Value.Value(nil); err == nil {
				for _, tag := range tags.([]interface{}) {
					f.Tag += " "+tag.(string)
				}
			}
		}
	}

	return f, nil
}

usage

type SomeObject {
   field1 String @goTag(tags: ["validate:email","gorm:field_1"])
   field2 Int @goTag(tags: ["validate:gt="])
}

[tprebs]

This issue can now be closed as there is a new directive extraTag for adding tags #1173