Property description is not respected for typed strings

[Leguu]

If you have a typed string, descriptions defined in JSONSchema and JSONSchemaExtend are not respected (they're dropped). In my application, I have a typed string that has a common description throughout the app, but jsonschema drops that custom description (I don't want to duplicate the description tag across many instances of that string).

Reproducing example:

type Bar string

func (Bar) JSONSchemaExtend(s *jsonschema.Schema) {
	s.Title = "This is a Bar title"
	s.Description = "I have a description!"
}

type Foo struct {
	BarProperty Bar
}

func main() {
	json, _ := jsonschema.Reflect(Foo{}).MarshalJSON()
	fmt.Println(string(json))
}

Current (invalid) output:

{"$schema":"https://json-schema.org/draft/2020-12/schema","$ref":"#/$defs/Foo","$defs":{"Foo":{"properties":{"BarProperty":{"type":"string","title":"This is a Bar title"}},"additionalProperties":false,"type":"object","required":["BarProperty"]}}}

Expected output:

{"$schema":"https://json-schema.org/draft/2020-12/schema","$ref":"#/$defs/Foo","$defs":{"Foo":{"properties":{"BarProperty":{"type":"string","title":"This is a Bar title","description":"I have a description!"}},"additionalProperties":false,"type":"object","required":["BarProperty"]}}}

Cause

I believe the issue is here, reflectStructFields calls structKeywordsFromTags which overwrites the description.

jsonschema/reflect.go

Line 524 in 328cc73

property.structKeywordsFromTags(f, st, name)

jsonschema/reflect.go

Line 609 in 328cc73

t.Description = f.Tag.Get("jsonschema_description")

Suggested fix

Struct property tags in general should overwrite the base schema, but we should check that the jsonschema_description tag is present before overwriting the description.

Change:

func (t *Schema) structKeywordsFromTags(f reflect.StructField, parent *Schema, propertyName string) {
	t.Description = f.Tag.Get("jsonschema_description")

	tags := splitOnUnescapedCommas(f.Tag.Get("jsonschema"))
        ...

To:

func (t *Schema) structKeywordsFromTags(f reflect.StructField, parent *Schema, propertyName string) {
	description, exists := f.Tag.Lookup("jsonschema_description")
	if exists {
		t.Description = description
	}

	tags := splitOnUnescapedCommas(f.Tag.Get("jsonschema"))
        ...